Clinical Anatomy and Operative Surgery of areas and organs of head, neck, chest and abdomen

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Ministry of Health of Ukraine

Ukrainian Medical Stomatological Academy

Clinical Anatomy and Operative Surgery of areas and organs of head, neck, chest and abdomen

Manual for training of specialists

for II (Master's Degree) in branch of knowledge 22 "Health Care"

on speciality 222 "Medicine"

S.M. Bilash, O.M. Pronina, M.M. Koptev

Poltava – 2018

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Ministry of Health of Ukraine

Ukrainian Medical Stomatological Academy

S.M. Bilash, O.M. Pronina, M.M. Koptev

Clinical Anatomy and Operative Surgery of areas and organs of head, neck, chest

and abdomen

Manual for training of specialists

for II (Master's Degree) in branch of knowledge 22 "Health Care"

on speciality 222 "Medicine"

Recommended by the Scientific Board of Ukrainian Medical Stomatological Academy as a manual for English speaking students of the higher educational

establishments of the Ministry of Health of Ukraine (protocol № 3 from 5.12.18)

Poltava – 2018

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2 UDC [611. 9+616-089](07)

Recommended by the Scientific Board of Ukrainian Medical Stomatological Academy as a manual for English speaking students of the higher educational establishments of the Ministry of Health of Ukraine (protocol № 3 from 5.12.18)

Authors: S. M. Bilash, O. M. Pronina, M. M. Koptev

Clinical anatomy and operative surgery of areas and organs of head, neck, chest and abdomen. Manual for training of specialists for II (Master’s Degree) in branch of knowledge 22 "Health Care" on specialty 221"Medicine".− Poltava:

Publishing office “Kopir servis”, 2018. – 186 р.

The manual on clinical anatomy and operative surgery for international students specializing in medicine corresponds to the syllabus and curriculum of the subject. The main issues for practical training and also recommendations on the methodology of the subject are represented sequentially. The manual includes theoretical material, assignments for self-control, situational tasks and the list of recommended literature for self-training.

It provides development of learning effectiveness of the students and is directed on mastering the subject "Clinical anatomy and operative surgery", gaining practical experience and skills which is of great importance in future medical practice.

Reviewers:

O.M.Slobodian – Doctor of Medicine, Professor, Head of Department of Anatomy, Topographic Anatomy and Operative Surgery, Higher State Educational Establishment of Ukraine "Bukovinian State Medical University";

Yu.I.Popovych – Doctor of Medicine, Professor, Head of Department of Clinical Anatomy and Operative Surgery, Ivano-Frankivsk National Medical University;

V.I.Liakhovskyi – Doctor of Medicine, Professor, Head of Department of Surgery No. 1, Ukrainian Medical Stomatological Academy;

O.M. Bieliaieva – PhD, Associate Professor, Head of Department of Foreign Languages with Latin Language and Medical Terminology, Ukrainian Medical Stomatological Academy.

Literary editor – I. V. Rozhenko Literature on medicine and biology

UDC [611. 9+616-089](07) ІSВІ 978-966-8716-54-6

S. M. Bilash, O. M. Pronina, M. M. Koptev

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CONTENTS

Introduction. Surgical instruments and suture equipment.

3 Primary surgical technique.

13 Clinical anatomy and operative surgery of the craniocerebral area of the head.

19 Clinical anatomy and operative surgery of the cranial cavity.

27 Simulation-based training surgery "Trepanation of the skull".

39 Clinical anatomy of the lateral facial part. Operative interventions in case of

purulent processes of the face. 43

Clinical anatomy of the anterior part of the face. Operative interventions in case of

purulent processes of the face. 61

Clinical anatomy of the neck regions. Fascias, triangles, neck vessels. Exposure

and bandaging of external and common carotid arteries. 69 Clinical anatomy of the neck organs (larynx, trachea, pharynx, esophagus, thyroid

gland). Tracheotomy. Thyroid gland surgery. 81

Clinical anatomy and operative surgery of the chest walls, mammary gland. Breast surgery. Access to the organs of the chest cavity. Resection of the rib. 95 Pleura, pleural cavity. Puncture of the pleural cavity. Pneumothorax. Surgical

management in case of pneumothorax. 101

Clinical anatomy and operative surgery of the lungs and organs of the anterior and

posterior mediastinum. 106

Clinical anatomy and operative surgery of the heart and pericardium.

111 Clinical anatomy and operative surgery of the anterolateral wall of the abdomen.

116 Clinical anatomy of the inguinal region. Surgical anatomy and surgical treatment

of inguinal hernias. 122

Surgical anatomy and operative treatment of the femoral, umbilical and linea alba

hernias. 129

Clinical anatomy of the abdominal cavity.

134 Clinical anatomy of the epigastric region.

142 Clinical anatomy of the hypogastric region.

148 Abdominal cavity surgery. Intestinal sutures. Resection of the intestine.

154 Educational simulation operation "Intestinal resection".

161 Stomach surgery

166 Surgery of liver, gallbladder, biliary tract, pancreas.

172 Removal of appendix. Surgery of the large intestine.

177

Final module control 182

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Academic discipline

Clinical anatomy and operative surgery

Module No.1 Clinical anatomy and operative surgery of the regions of head, neck, chest and abdominal cavity.

Content module No.1

Introduction to clinical anatomy and operative surgery. Clinical anatomy and operative surgery of areas and organs of head and

neck.

Topic 1 Introductory lesson. Surgical instruments and suture equipment.

Year II

Faculty Foreign students training (medical)

1. The relevance of the topic

Every surgical intervention, regardless of the complexity and region, is performed by surgical instruments and requires high-quality suture materials.

Profound knowledge of surgical instruments and rules of their use are important in professional activities of specialists in different fields of surgery that should be combined with knowledge of rules and surgical techniques.

2. Specific objectives

1. Classify general surgical instruments.

2. Explain the technique of general surgical instruments application.

3. Classify surgical suture materials.

4. Explain the use of basic types of suture materials.

3. Tasks for independent work to prepare for the lesson

3.1. List of the main terms, parameters, characteristics that should be learnt by the student while preparing for the lesson

Term Definition

Operative surgery

The science dealing with surgical operations, methods of surgical interventions, which provides mechanical effect on organs and tissues with diagnostic, medical or reconstructive

purpose

Clinical anatomy

Science dealing with anatomical issues which are relevant to various fields of practical medicine.

Topographic anatomy

The science dealing with structure, shape and relative location of organs and tissues in various parts of the human body

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Developmental anatomy

The science that studies the age-related aspects of anatomical features of individual human development – ontogenesis. The branch of anatomy that studies structural changes of an

individual from fertilization to maturity Comparative

anatomy

The science that studies similarities and differences in the body structure of animals and humans, the body structure itself at different stages of evolution, that clarifies the historical development of human organism − phylogenesis

General surgical

instruments Surgical instruments used for all types of surgery

Special surgical

instruments Surgical instruments used only for certain surgical interventions on the organs

3.2. Theoretic questions

1. What is the order of instruments placement on the table of scrub nurse?

2. What types of scalpels do you know? What positions for holding a scalpel do you know?

3. What is a scalpel position while performing the skin incision?

4. How should the scissors be held in the hand while dissecting tissue?

5. What is the difference between Kocher’s and Billroth’s hemostatic forceps?

6. What is the difference between Hegar’s, Troianov, and Mathieu needle holders?

7. Is it correct position of the forceps in the hand when its end is directed to the palm?

8. What types of surgical needles do you know?

9. What are the requirements for suture material?

10. What is the classification for suture materials? What are their comparative characteristics?

3.3. Practical skills acquired in class

1. Arrange the instruments on the table of scrub nurse.

2. Perform the soft tissue cutting with a scalpel.

3. Apply hemostatic forceps on the blood vessels.

4. The content of the topic

At the beginning of the lesson the teacher should acquaint students with educational facilities of department, equipment, main tasks of the department in teaching and research work.

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Description of surgical instruments

Starting with surgical instruments, the teacher explains that there are general and special instruments and surgical suturing devices, proceeds to description of each instrument specifying its application in surgical practice and the way of its application.

General surgical instruments can be distributed into the following groups: for tissue separation (cutting instruments), for bleeding arrest (hemostatic instruments), auxiliary (fixing) instruments and instruments for tissue connecting.

Instruments for tissue separation include scalpels (bellied, sharp-pointed, straight).

When dissecting tissue surgeons often use scissors: straight or curved along the plane or edge. There are scissors for special purpose: ocular, vascular and others.

Hemostatic instruments include clamps, which can have straight or curved working surface. Kocher’s clamps are widespread in surgical practice (with teeth on working surface), Mikulich’s (with teeth and diagonal notches on working surface) and Billroth’s (without teeth). Hemostatic clips "mosquitoes" are used for small vessels bleeding arrest. Halstead clamps provide simultaneous capture of both vascular wall and adjacent tissue.

Auxiliary (fixing) instruments are used to examine occurring wound, identify bleeding vessels, pathologically changed tissues and organs by thorough widening of the wound edges. It is performed by capturing the wound edges with fixing tools, namely, tweezers, hooks, mirrors etc.

Hooks can be sharp-pointed, blunt, laminar, one-, two-, three- and four toothed.

If surgeon manipulates in the depth of the wound near large vessels and nerves, it is advisable to use blunt or laminar hooks.

Tweezers are often used as fixing instruments. Anatomical forceps (without teeth) is preferable in case of soft tissue capture (blood vessels, nerves, walls of the intestines and others), and surgical ones are used while capturing the edges of dissected skin, aponeurosis, tendons.

The group of auxillary (fixing) instruments includes probes, namely, grooved, bulbous-end and Kocher probe. Grooved probes are used in cutting of aponeurosis and fascia, the bulbous-end – to examine the depth and direction of the wound channel or fistule, detection of foreign bodies and other. Kocher probe is used in thyroid gland surgery.

Deshana ligature needles also belong to auxiliary group of instruments. They are used to bring the ligature under the vessels and ducts. There are right and left- handed Deshana needles, they can be sharp-pointed and blunt-ended.

Instruments for tissue connection include needle holders (Hegar's, Troianov, Mathieu), curved surgical needles (taper and cutting), straight, pointed and blunt (for liver), clamps, tweezers and Michel clips remover.

Cutting (triangular) surgical needles are used in case of suturing the skin, aponeurosis, fascia and taper (round) one – while suturing the walls of hollow and parenchymatous organs.

Atraumatic needles are used for angiorrhaphy, suturing of the heart and lung wounds.

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The teacher indicates the order of instruments placement on the table of scrub nurse, rules for passing them to the surgeon and how the surgeon should hand back the instruments to the nurse.

Fig.1. Instruments for tissue connection:

A − needle holders: 1 − for angiorrhaphy; 2 − with bent handles and ratchets; 3 – Troianov’s; 4 − with straight ring handles and ratchets; 5 − curved with straight ring handles and ratchets; 6, 7 − straight and curved with straight ring handles and ratchets; B − surgical needles: 1 − surgical needles straight and curved (cutting and taper); 2 − atraumatic surgical needle; 3 − the metal clips (Michel); 4 − forceps for metal clips applying.

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Fig.2. Auxiliary tools:

B – retractors: 1 – liver speculum; 2 – abdominal wall speculum; 3 –

kidney abduction

speculum; 4 – soft tissue elevator; 5 – speculum for heart; 6 – Buial'skii spatula; 7 – surgical toothed hooks; 8 – laminar hooks; C – retractors: 1 – double with ratchet; 2 – without ratchet; 3 – screw

retractor used for ribs.

The teacher shows different positions of scalpel fixing (dinner knife position, pen holding position, fiddlestick position, amputating knife position) depending on the objectives of the incision (Fig.3−8).

Fig.3. Dinner knife position of the scalpel

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Fig.4. Pen holding position

Fig.5. Fiddlestick position

Fig.6. Position like amputation knife

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Fig.7. Dissection of the leg soft tissues using amputation knife

Fig.8. Position of scissors in the surgeon's hand

The teacher should draw attention to certain types of special surgical instruments, namely, retractors, tongue forceps, tracheostomic cannulas, intestinal clamps, trocars, liver speculum, and the like.

The first practical lesson in each academic group includes presentation of topics

"General surgical instruments", "Special surgical instruments", suturing surgical devices and instruments for blood vessels suturing (Fig.1, 2).

5. Materials for self-control A. Tasks for self-control:

Test No.1. The scrub nurse gave the surgeon bellied scalpel instead of required sharp- pointed one. What is the main difference between them?

a) length of handle;

b) thickness of handle;

c) length of working part;

d) sharpness of blade;

e) angle of the point.

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Test No. 2. The surgeon used Billroth clamp, curved along the edge during surgery.

What is it used for?

a) separation of tissues;

b) bleeding arrest;

c) separation of wound edges;

d) providing surgery technique;

e) connection of tissue.

Test No. 3. The surgeon used scissors while separating tissues. Scissors were fixed in the hand in such a way, that the thumb of the surgeon was in one of two rings. What finger of the surgeon should be in the second ring of the instrument to provide optimal fixation in the hand?

a) 1^st; b) 2^nd; c) 3^rd; d) 4^th; e) 5^th.

Test No. 4. On the table for general surgical instruments of scrub nurse the following instruments were placed: scalpels, scissors, haemostatic clamps, hooks, tweezers, packer, towel clips, grooved probe, Luer cannula, Hegar needle holders, needles, suture material and gauze wipes. What should not be on the table?

a) hooks;

b) packer;

c) towel clips;

d) grooved probe;

e) Luer cannula.

Test No. 5. While performing surgical access the surgeon dissect aponeurosis. What hooks should be used for separation of aponeurosis edges?

a) sharp single-toothed;

b) blunt single-toothed;

c) sharp multi-toothed;

d) blunt multi-toothed;

e) Farabeuf hook.

B. Tasks for self-control:

Task No. 1. For removal of foreign body from the gastrocnemius muscle the scrub nurse placed cutting, auxiliary and connecting tissues instruments. Is it possible to start a foreign body removal surgery with these instruments?

Task No. 2. The surgeon used pointed scissors for skin dissection during surgery.

What mistake was made?

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References Basic literature

1. Tsyhykalo O.V. Topographic Anatomy and Operative Surgery / O.V.Tsyhykalo.

– Vinnytsia, 2011. — 528 р.

2. Danilchenko S.I. Methodical Instruction For the 3st year students’of stomatological faculty self - preparation work (at class and at home) in studying operative surgery and toographical anatomy / S.I.Danilchenko, E.N.Pronina, O.Yu.Polovik. - Poltava, 2010. — 239 р.

Additional literature

1. Gray. Н. F.R.S. Gray’s anatomy / Henry F.R.S. Gray, R. A. Bolam. – London, 1994. – 1290 p.

2. McCraw J.B. Athlas of muscle and Musculocutaneous Flaps Head and Neck Reconstruction / John B McCraw, Phillip G Arnold. – Norfolk, Virginia, 1988. – 757 р.

3. Netter F. H. Atlas of Human Anatomy / Frank H.Netter. – East Hannover, New Jersey, 1990. – 592 р.

4. Hnatyuk M.S. Operative surgery and topographical anatomy (lectures) / M.S.Hnatyuk, O.B.Slabui. – Temopil, 2004. – 212 р.

5. Bernard C. Illustrated Manual of Operative Surgery and Surgical Anatomy / C.Bernard – 1991.-330 р.

6. Pemberton L.B. Workbook of Surgical Anatomy / L.B.Pemberton. – 1990. – 298 р.

7. Gliedman M.L. Atlas of Surgical Techniques / M.L.Gliedman. – New York etc., McGraw – Hill. – 1990. – 420 р.

8. Sabiston D.C. Atlas of General Surgery / D.C.Sabiston. – Philadelphia etc., Saunders. – 1994. – 220 р.

9. Chassin J.L. Operative Strategy in General Surgery / J.L.Chassin. – New York etc., Springer. – 1994. – 368 р.

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1. The relevance of the topic

Every surgical intervention, regardless of the complexity and region, is performed by surgical instruments and requires high-quality suture material.

Profound knowledge of surgical instruments and rules of their use is important in professional activities of specialists in different fields of surgery that should be combined with knowledge of rules and surgical techniques.

2. Specific objectives:

1. Explain how to prepare the surgical field.

2. Explain how to carry out layer by layer infiltration anesthesia.

3. Explain how to carry out layer by layer separation of tissues.

4. Explain how to carry out layer by layer connection of tissues.

5. Explain the technique of bleeding arrest using hemostatic clips and ligatures on the vessels.

3.1. List of the main terms, parameters, characteristics that should be learnt by the student while preparing for the lesson

Operative surgery

The science of surgical operations, methods of surgical interventions, the essence of which is to mechanical action on organs and tissues with a diagnostic, therapeutic or restorative purpose

Topographical anatomy The science dealing with structure, shape and relative location of organs and tissues in various parts of the human body.

Academic discipline

Module No.1 Clinical anatomy and operative surgery of the sites of the head, neck, chest cavity and abdominal cavity.

Content module No.1

Introduction to clinical anatomy and operative surgery.

Clinical anatomy and operative surgery of the head and neck

Topic 2

Primary surgical technique

Year II

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Special surgical instruments Surgical instruments used only for certain surgical interventions on the organs.

3.2. Theoretic questions:

1. What are the surgical hand scrub techniques?

2. How is operating field prepared for surgery?

3. What are the methods for local anesthesia?

4. What is Vishnevsky anesthesia?

5. What types of scalpels do you know? Positions of scalpel holding.

6. What is the scalpel position for skin incision?

7. How should scissors be held in the hand when dissecting tissue?

8. What is the difference between Kocher hemostatic clamp and Billroth clamp?

9. What is the difference between Hegar's needle holders, Troyanov and Mathieu needle holders?

10. Define whether the position of tweezers in the hand is correct, if its end is directed to the palm of the hand.

11. What types of surgical needles do you know?

12. What are the requirements for suture material?

13. How can suture materials be classified? Name their comparative characteristics:

biological, synthetic, absorbable and non-absorbable?

14. What main types of surgical knots are used in practice?

15. What is the basic principle for tissue disconnection?

16. How should the skin, fascia, muscles be disconnected?

17. What is the principle of tissue connection?

18. What are the types of skin sutures?

19. What instruments are needed for injections and infusions?

3.3. Practical activities performed in class:

1. Surgical scrubbing of the surgeon's hands.

2. Preparation of operating field and surgical draping, namely, placing of sterile coverings on it.

3. Layer by layer tissue disconnection.

4. Bleeding arrest in the surgical wound.

5. Layer by layer connection of tissues.

6. Tying of main types of surgical knots.

4. Content of the topic:

Preparation of operating field

Surgery starts with preparation of operating field. Hair should be removed by special cream − depilator. The skin of the surgical field should be disinfected twice by 70% of alcohol, and then by 2% solution of iodine. It should be noted that iodine causes skin irritation and may be an allergen, so, now it is rarely used. Alcohol solutions of iodophores (iodonate, betadine, betazidone, iodopirone) are used more often. Alcohol solution of Gibitanum, Roccal and peracetic acid can also be used.

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The skin of the surgical field should be isolated by sterile sheets or self-adhesive sterile drapes, through which surgical incisions are performed.

In general, during operation, the surgical field is disinfected 4 times (according to Grossikh-Filonchikov):

• before conducting the local anesthesia, or placing of sterile coverings (for general anesthesia);

• before layer by layer tissue dissection (performing of operative access);

• before skin suturing (after all stages of surgery);

• before applying an aseptic dressing on the surface of the surgical wound.

The technique for conduction of layer by layer local infiltration anesthesia The teacher explains that there are two types of anesthesia: general and local, and then assigns the scrub nurse, surgeon and assistant from the number of students. The scrub nurse places syringe, injection needles, and other instruments required for local anesthesia on the table for instruments. The surgeon and assistant at this time occupy appropriate places and start disinfection of operating field, perform surgical draping.

The teacher emphasizes priority of domestic authors in development of local anesthesia methods, points out the principles of anesthesia by the method of Vishnevsky creeping infiltration.

Layer by layer tissue disconnection

The teacher draws attention to sparing performing of incisions, taking into account direction of skin folds, muscle fibers, topography of neurovascular bundles.

Incision is usually performed with bellied scalpel, fixing the skin at the moment of incision by the fingers of the left hand. After skin incision, the edges of the wound are dilated with sharp hooks and bleeding arrest from damaged blood vessels should be performed. Then subcutaneous tissue, superficial and proper fascia are incised.

Large vessels and nerve trunks can be located under the proper fascia, so, they are incised through a grooved probe. Vessels and nerves that are in the direction of incision, if possible, are drawn aside. Fascia propria can also be incised with blunt scissors, bringing in the lower branch of the scissors below the fascia.Disconnection of muscles, if possible, is performed according to blunt pattern in direction of the muscle fibers, if necessary, the muscles are incised. Periosteum is incised with scalpel, then the edges of the periosteum are exfoliated with straight or curved raspatory. Periosteum should be retained as much as possible, as in future it will provide regenerative function. Currently, laser devices "Scalpel-1", "Scalpel-2",

"Romashka" are used in surgery.

Suturing

The first series of continuous sutures (simple, locking, mattress) students perform on fascia propria. Assistant shows how to tie the knot properly while suturing. Students put loop stitches on the skin. The distance from the edge of incision is 0.3−0.5 cm. The wound edges are carefully put together. The distance from one knot to another is about 1 cm (Fig. 9, 10, 11).

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Fig.9. Intracutaneous continuous suture

Fig.10. Tying the surgical knot on apposed wound edges

Fig.11. Stringing of dense skin on the needle with tweezers

Test No. 1. The surgeon has performed the operation. Which should be the sequence of its stages?

a) access, procedure, exit;

b) access, exit, procedure;

c) procedure, access, exit;

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d) procedure, exit, access;

e) exit, procedure, access.

Test No. 2. Surgeon is performing surgical access. What does this stage of surgical intervention include?

a) access to the organ or formation where the intervention is performed;

b) examination of adjacent organs or formations in surgical field;

c) preparation of organs or formations for intervention;

e) action pertaining the organ or formation where the intervention is performed;

d) connection the tissues.

Test No. 3. Surgeon is performing operative procedure. What does this stage of surgical intervention include?

b) examination of adjacent organs or formations in the operational field;

d) action pertaining the organ or formation where the intervention is performed;

e) connection the tissues.

Test No. 4. Surgeon is performing operative exit. What does this stage of surgical intervention include?

b) examination of adjacent organs or formations in the operational field;

d) action pertaining the organ or formation where the intervention is performed;

e) connection the tissues.

Test No. 5. The scrub nurse placed general surgical instruments on the sterile table.

What instruments should be on this table?

a) for tissue separation;

b) for tissue disconnection and bleeding arrest;

c) for tissue disconnection, bleeding arrest and auxiliary;

d) for tissue disconnection, bleeding arrest, auxiliary and for tissue connection;

e) for tissue disconnection, bleeding arrest, auxiliary and special.

Task No. 1. While making incision of the skin and subcutaneous tissue, uneven, jagged edges of the wound were formed. What rule did the surgeon ignore while incising the skin?

Task No. 2. When removing a foreign body, the surgeon disinfected the surgical field with 96 ° alcohol and performed its sterile draping. Was the preparation of surgical field carried out correctly?

Task No. 3. The final bleeding arrest in the wound was performed with Kocher's clamp, which assistant applied on bleeding vessel; surgeon lifted the ligature to the

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clamp without removing the clamp, tied the vessel with two knots. When assistant removed the clamp, bleeding started again. What was the mistake?

Task No. 4. Three hours after stitching the wound the severe bleeding occured. How can this be explained?

Task No. 5. While suturing the wound the surgeon used silk ligature and tightened knot strongly. Did he connect the edges of damaged muscle correctly?

Task No. 6. While connecting the edges of wound, surgeon made the cavity in subcutaneous tissue. The skin was sutured with knot stitches. Was the tissue connection performed properly?

Task No. 7. When applying the interrupted sutures on the skin of the wound, that is 12 cm in length, an area of excess skin was formed at the angle of the wound. What mistake has the surgeon done?

Task No. 8. In 48 hours after suturing the skin, marginal necrosis occured. What caused it?

1. Tsyhykalo O.V. Topographic Anatomy and Operative Surgery / O.V.Tsyhykalo. – Vinnytsia, 2011. — 528 р.

2. Danilchenko S.I. Methodical Instruction For the 3st year students’of stomatological faculty self - preparation work (at class and at home) in studying operative surgery and toographical anatomy / S.I.Danilchenko, E.N.Pronina, O.Yu.Polovik. - Poltava, 2010. — 239 р.

4. Hnatyuk M.S. Operative surgery and topographical anatomy (lectures) / M.S.Hnatyuk, O.B.Slabuj. – Temopil, 2004. – 212 р.

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Academic

discipline Clinical anatomy and operative surgery

Content module No.1 Introduction to clinical anatomy and operative surgery.

Clinical anatomy and operative surgery of the head and neck.

Topic 3

Clinical anatomy and operative surgery of the craniocerebral region of the head. Borders, external

hallmarks. Head shape, age features. Division into regions:

fronto-parieto-occipital, temporal, mastoid process region.

Layers of the cranial vault, cellular spaces, blood supply and innervation, lymphatic drainage. Trepanation of the Chipault triangle. Primary surgical debridement of craniocerebral wounds. Antrotomy.

Year II

1. The relevance of the topic: traumas of the head soft tissues, penetrating and nonpenetrating wounds of the cranial vault, hematomas of different localization, intracranial tumors can often be found in surgical practice. A good knowledge of the anatomical and physiological features of the soft tissues of fronto-parieto-occipital, temporal, mastoid process regions is essential for correct opening of hematomas, abscesses and phlegmons. In addition, it will help to understand the peculiarities of the course of pathological processes and use optimal surgical techniques in the treatment.

2. Specific objectives.

1. Explain the topography of the vessels and nerves of the cranial vault, the regions of their location for carrying out conduction anesthesia, dissection of flaps

when performing surgical interventions.

2. To analyze the features of the layered structure of the cranial vault tissues.

3. To analyze the ways of development of phlegmon, purulent edema, hematoma on the cranial vault.

4. Explain connections of the craniocerebral subcutaneous veins with the sinuses of dura mater.

5. Explain how to perform primary surgical debridement of the craniocerebral wounds.

6. Explain the technique of bleeding arrest from blood vessels of the subcutaneous tissue, skull bones, cerebral meninges and venous sinuses.

7. Explain the borders of the Chipault triangle trepanation.

8. Explain the antrotomy technique.

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3.1. List of the main terms, parameters, characteristics that should be learnt by the student while preparing for the lesson.

Antrotomy Trepanation of the mastoid process Trepanation of the

Chipault triangle

The region of the mastoid process, within which anthrotomy is performed

1. The head borders. Craniocerebral and facial parts of the head. Their division into regions.

2. Sections of the cranial vault and their borders.

3. The borders of the frontal-parietal-occipitalregion.

4. Layers of the fronto-parieto-occipital region.

5. Vessels and nerves of the fronto-parieto-occipital region.

6. The borders of temporal region.

7. Layers of the temporal region.

8. Cellular spaces of the temporal region.

9. Vessels and nerves of the temporal region.

10. Borders and layers of the mastoid region.

11. The borders of the Chipault triangle trepanation.

12. Technique of antrotomy. Common errors and complications.

3.3. Practical skills acquired in class:

1. To master layer preparation of the studied regions.

2. To diagnose subaponeurotic and subperiostal abscesses and hematomas of cranial vault on the basis of obtained knowledge.

3. To determine the possible ways of spreading of purulent infection from the cellular layers of temporal region.

4. To identify the borders of the Chipault triangle trepanation and specify the possible complications.

5. To perform primary surgical debridement of cranial wounds and trepanation of mastoid process.

4. The content of the topic:

Frontal-parietal-occipital region

At the beginning of the class students analyze studied information, namely, borders and layered structure of fronto-parieto-occipital regions and start preparation of this region (Fig.12).

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Fig.12. Layers of the cranial vault presented in frontal section, conducted through the fronto-parieto-occipital region (scheme by S.N. Delitsyn, with changes).

1 − skin; 2 − subcutaneous tissue; 3 − epicranial aponeurosis; 4 − diploic vein; 5 – subaponeurotic cellular tissue; 6 − periosteum; 7 – subperiosteal cellular tissue; 8 − arachnoidal granulations; 9 − blood accumulated in the extradural space due to the middle meningeal artery damage (10); 11 – dura mater; 12 − arachnoidea mater encephali; 13 − cerebrospinal fluid of the subarachnoideal space; 14 − pia mater; 15 − cortex of the cerebral hemispheres; 16 − falciform process of dura mater; 17 – superior sagittal sinus of dura mater; 18 − brain veins; 19 − artery and vein of dura mater; 20 − extradural space; 21 − internal plate of parietal bone; 22 − spongy substance; 23 − external plate of parietal bone; 24 − vena emissaria parietalis; 25 − subcutaneous vessels; 26 − septa of connective tissue joining the skin with epicranial aponeurosis.

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On the frontal, parietal or occipital part of the head, the shape of an imaginary flap is indicated. It is important to emphasize that the flap, which is cut out, should be directed downward. This provides sufficient blood supply to the flap and its engraftment.

Students separate the skin and subcutaneous cellular tissue along with aponeurosis. Special attention should be paid to the skin connection with aponeurosis through connective tissue strands extending from the skin to aponeurosis. The connection of the subcutaneous blood vessel walls with connective tissue strands and the possibility of prolonged vascular bleeding should be determined. The teacher gives a description of the scalp wounds on the cranial vault. After cutting out the aponeurotic flap, students insert a Kocher probe between the aponeurosis and periosteum. Moreover, students should check the friability of subaponeurotic cellular tissue. The next stage is dissection of the cranial vault periosteum.

Due to the presence of the subperiosteal loose layer, the periosteum is easily exfoliated from the bone.

Students study the structure of the bone on the sagittal skull cut. It should be mentioned that the thickness of the inner lamina is very important while damaging the bones of the skull in case of the brain area traumas. In the process of fronto- parieto-occipital region preparation, attention should be paid to the radial direction of the neurovascular bundles.

Thus, summing up the information about the layer-by- layer structure of the cranial vault tissues, it should be noted that each layer is followed by a fiber layer:

skin − subcutaneous tissue, epicranial aponeurosis − subaponeurotic tissue;

periosteum − subperiosteal tissue. The first three layers are connected with each other by vertical connective tissue septums. The bones of the vault consist of the outer, inner laminae and diploe between them.

The blood flow to the frontal-parietal-occipital region is carried out by the arteries: supraorbital, suprathrochlear, superficial temporal artery and its branches (frontal and parietal), posterior auricular and occipital. Innervation: n. supraorbitalis, n. suprathrochlearis, n. auriculotemporalis, n. auricularis major, n. occipitalis major and n. occipitalis minor.

Temporal region

In the temporal region, a lingulate flap with a width 2.5 cm and 4 cm in length are cut out. First, the students separate the skin from the deeper tissues. Pay attention to the absence of pronounced epicranial aponeurosisin this region. The latter is thinned and defined as superficial temporal fascia. After detaching the skin with subcutaneous tissue and superficial fascia, the students isolate the temporal fascia, separate its surface and deep plates and make sure that there is a closed cellular space between them above the zygomatic arch. After this, they dissect the deep plate of the temporal fascia, introduce a Kocher probe, penetrating zygomatic arch, and make sure in connection between the subaponeurotic tissue and the fatty body of the cheek.

After detaching the subfascial layer, the students cut out a lingulate flap of the temporal muscle and exfoliate it. On the posterior surface of the temporal muscle, they prepare the branches of deep temporal artery and the same name nerve. Between the muscle and periosteum, a deep layer of loose tissue of the temporal region is exposed. The next stage is periosteum dissection.

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At the bone preparation, students study the structure of the temporal bone squama. Pay attention to the presence of a furrow for the middle meningeal artery, the possibility of damage to this artery due to the injuries of the temporal bone.

Blood supply of the site: the superficial temporal artery and its branches, as well as deep temporal branches of the maxillary artery.

Innervation: auriculotemporal nerve and facial nerves, deep temporal branches of the mandibular nerve.

Mastoid region

On the bone preparation students examine the boundaries of the site corresponding to the mastoid process (Fig.13). After that, students perform the layer- by- layer preparation of the mastoid region. Pay attention that the skin is thin, has a strong connection with deeply placed aponeurosis.

Fig.13. Trepanation of the mastoid process

A− line for soft tissues cutting according to Schwarz;

Б− scheme of the Chipault triangle on the skeletonized process: 1− middle cranial fossa; 2− main mastoid air cells; 3− sinus cavernosus; 4− facial nerve;

B− trepanation technique.

In the process of preparation, it should be noted that the periosteum has a close connection with the bone. On the mastoid process cut, they study the structure, possible pneumatic or sclerotic forms of structure of its cells. The presence of the largest cell – antrum is detected.

On the bone preparation students study the boundaries of theChipault triangle, within which the trepanation of the mastoid process – anthrotomia should be performed.

Primary surgical treatment of craniocerebral wounds

Craniocerebral injury is the indication for the primary surgical treatment of craniocerebral wounds. It is noted that the aim of this operation is to transform the infected wound into uninfected. The signs of penetrating and impenetrable craniocerebral wounds should be determined. So, in case of damage to the dura mater, wounds are considered to be penetrating, and if integrity is preserved, they are

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impenetrable. The main stages of primary surgical treatment for craniocerebral wounds are as follows:

• removal of the foreign bodies, bone fragments, treatment with antiseptics, anesthesia;

• layer-by-layer removal of non-viable wound edges within the healthy tissues;

• conducting a thorough hemostasis;

• examination of the wound bottom.

Only the fragments of bones that are not fixed to the periosteum, along with the extraneous bodies, should be removed.

During the layer-by-layer treatment of craniocerebral wounds, special attention is paid to the state of the dura mater. If it is not damaged, pulsates, has no signs of subdural hematomas, then it is not dissected. At the end of the surgery, the stitches are put into aponeurosis; the skin is not stitched or fixed with thin sutures.

In case of penetrating wound, the arcuate incision is performed on the dura mater, the bone fragments, foreign bodies, blood clots are removed from the medullary substance.

The crushed brain tissue (detritus) and small bone fragments in it are washed away with a stream of the physiological solution using a rubber bag. After a thorough hemostasis, the dura mater is sutured. If it is not possible (significant defects of the dura mater), it is not stitched, thin sutures are put into aponeurosis, as well as the skin, the rubber tube drainages are left in the wound angles for 1-2 days.

Test No. 1. The injured person has a cut wound in the anterior part of the fronto- parieto-occipital region. What is the front boundary of this region?

a) linea nuchae superior;

b) nasal bridge and superciliary arch;

с) linea temporalis superior;

d) linea temporalis inferior;

e) seam between the parietal and frontal bones.

Test No. 2. The patient has an abscess 2 x 2 cm in size in the frontal-parietal- occipital area. In what layer is the inflammatory process localized in this case?

a) intradermal;

b) in subcutaneous tissue;

c) interaponeurotic tissue;

d) subaponeurotic tissue;

e) subperiosteal tissue.

Test No. 3. The doctor determined the pulse of the patient on the superficial temporal artery. Where is the pulsation point of this artery?

a) for 1 transverse finger in front of the ear tragus;

b) for 1 transverse finger behind the ear;

c) 2 cm behind the mastoid process;

d) along the anterior edge of the masseter muscle;

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e) over the ear.

Test No. 4. A patient has a purulent mastoiditis. The surgeon cuts the abscess. What section will be the most anatomically reasonable and least traumatic in this case?

a) transverse;

b) longitudinal;

c) radial to the vertex;

d) radial to ear tragus;

e) arcuate.

Test No. 5. A patient has an abscess in the left temporal region. The surgeon cuts the abscess. What section will be the most anatomically reasonable and least traumatic in this case?

a) transverse;

b) longitudinal;

c) radial to the vertex;

d) radial to ear tragus;

e) arcuate.

Task No. The patient M. was brought to the emergency hospital with complaints of headache, swelling in the area of the cranial valt. The patient slipped and fell two hours ago. The examination revealed the presence of fluctuating swelling, limited by the front edge of the orbit, posteriorly − by the upper nuchal line, on the sides − the upper temporal line. Diagnosis: hematoma of the cranial vault. In what cellular tissue layer is hematoma localized?

Task No. 2. During anthropometry, the surgeon went beyond the posterior borders of Chipault triangle. Heavy bleeding occurs. What is the source of bleeding?

Task No. 3. During anthrotomy, paralysis of the facial muscles on the side of intervention (left-sided anthrotomy) occurred in the patient. What is the cause of this complication?

Task No. 4. After an injury to the skull, a palpable fluctuating tumor within the boundaries of the left temporal bone was observed. Where is hematoma located?

Task No. 5. During anthrotomy, the surgeon went beyond the borders of Chipault triangle. What formations can be damaged in this case?

1. Tsyhykalo O.V. Topographic Anatomy and Operative Surgery / O.V.Tsyhykalo. – Vinnytsia, 2011. — 528 р.

2. Danilchenko S.I. Methodical Instruction For the 3st year students’of stomatological faculty self - preparation work (at class and at home) in studying operative surgery and toographical anatomy / S.I.Danilchenko, E.N.Pronina,

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O.Yu.Polovik. - Poltava, 2010. — 239 р.

4. Hnatyuk M.S. Operative surgery and topographical anatomy (lectures) / M.S.Hnatyuk, O.B.Slabuj. – Temopil, 2004. – 212 р.

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Academic discipline

Content module No.1 Introduction to clinical anatomy and operative surgery.

Clinical anatomy and operative surgery of the head and neck.

Topic 4

Clinical anatomy and operative surgery of the cranial cavity. Base of the skull: external and internal. Cranial fossae, their contents. Topography of the brain meninges and venous sinuses of the dura mater of the brain. The scheme of craniocerebral topography (Kronlein-Briusova- Yehorov). Trepanation of the skull.

Year II

1. The relevance of the topic: the treatment of injuries to the skull, hematomas, posttraumatic hypostases of the brain, tumors, cysts demands the substantial knowledge of topography of the main furrows (sulci) of the brain and cerebral gyri, schemes of the craniocereberal topography, as well as the knowledge of technique for conducting the surgical interventions and the bleeding arrest from the vessels.

2. Specific objectives.

1. Explain the topography of the external and internal bases of the skull, cranial fossae and their contents.

2. Explain the topography of the cerebral meninges and venous sinuses of the cranial dura mater.

3. Draw a scheme of the cranio-cerebral topography according to Kronlein-Briusova, Yehorov.

4. Analyze the various methods of trepanation (craniotomy, craniectomy) of the skull.

5. Explain the technique of cranioplasty conducting in the parietotemporal region.

3.1. List of the main terms, parameters, characteristics that should be learnt by the student while preparing for the lesson.

Primary surgical treatment of the brain

wounds

Trepanation of the skull

The surgical intervention, which involves the transformation of the wound of the brain part of the head from the dirty (infected) into a clean and creating the proper conditions for healing by its primary tension.

Opening of the cranial cavity for operative access to the brain and its meninges in case of surgical intervention.

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1. Blood supply of the brain.

2. Cranio-cerebral topography scheme according to Kronlein-Briusova.

3. Special surgical tools for interventions on the brain part of the head.

4. Types of anesthesia in case of brain interventions.

5. Methods for bleeding arrest from the sinuses of the cranial dura mater.

6. Technique for bleeding arrest from the brain vessels.

7. Primary surgical treatment of penetrating head injuries.

8. Cranioplasty of the parieto-temporal region.

9. Decompressive trepanation of the skull according to Cushing.

3.3. Practical skills acquired in class:

1. Perform the osteoplastic trepanation of the skull on the corpse.

2. Be able to stop bleeding from the middle meningeal artery and sinuses of the dura mater of the brain.

4. The content of the topic:

Topographic and anatomical features of the external and internal skull base While making the analysis of the topography of the external and internal base of the skull, students pay attention to the bones forming the cranial fossae.

Thus, the anterior cranial fossa on the inner base of the skull is separated from the middle by the posterior margin of the lesser wings of the sphenoid bone. It is formed by two orbital surfaces of the frontal bone with the cribriform lamina (lamina cribrosa) of the ethmoid bone; the body and the lesser wings of sphenoid bone complement the fossa.

Attention should be drawn to the fact that the anterior cranial fossa is located above the nose cavity and orbits. It contains frontal lobes of the brain and olfactory bulbs (bulbus olfactorius) which are located underneath them on the sides of the crista galli on the cribriform plate of ethmoid bone. About 30 nerve trunks pass to them from the nose cavity through the holes in the cribriform lamina. The anterior and posterior ethmoidal arteries (aa. ethmoidales anterior et posterior) and ethmoidal nerves (nn. ethmoidales) pass through these holes in the mucous membrane of the nasal cavity. The anterior meningeal artery (a. meningea anterior) passes from the anterior ethmoidal artery to the dura mater. It is emphasized that foramen caecum through which the venous plexus of the nasal cavity is connected with the superior sagittal venous sinus (sinus sagittalis superior) is located in front of crista galli.

At the base of the lesser wings of sphenoid bone the paired optic foramina are located, through which the optic nerves (n. opticus) and the ophthalmic artery (a.

ophtalmica) without a vein of the same name pass from the cavity of the skull to the orbit.

The middle cranial fossa (fossa cranii media) consists of three bones – the sphenoid bone and the two temporal bones. Anteriorly and laterally it is bounded by the lesser wings of the sphenoid bone. These are two triangular projections of bone that arise from the central sphenoid body. Anteriorly and medially it is bounded by the limbus of the sphenoid bone. The limbus is a bony ridge that forms the anterior border of the chiasmatic sulcus (a groove running between the right and left optic

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canals). Posteriorly and laterally it is bounded by the superior border of the petrous part of the temporal bone. Posteriorly and medially it is bounded by the dorsum sellae of the sphenoid bone. This is a large superior projection of bone that arises from the sphenoidal body. The floor is formed by the body and greater wing of the sphenoid, and the squamous and petrous parts of the temporal bone. The middle cranial fossa consists of a central portion, which contains the pituitary gland, and two lateral portions, which accommodate the temporal lobes of the brain.

The central part of the middle cranial fossa is formed by the body of the sphenoid bone. It contains the sella turcica which is a saddle-shaped bony prominence. It acts to hold and support the pituitary gland, and consists of three parts:

1) the tuberculum sellae (horn of the saddle) is a vertical elevation of bone. It forms the anterior wall of the sella turcica, and the posterior aspect of the chiasmatic sulcus (a groove running between the right and left optic canals);

2) the hypophysial fossa or pituitary fossa (seat of the saddle) sits in the middle of the sella turcica. It is a depression in the body of the sphenoid, which holds the pituitary gland;

3) the dorsum sellae (back of the saddle) forms the posterior wall of the sella turcica. It is a large square of bone, pointing upwards and forwards. It separates the middle cranial fossa from the posterior cranial fossa.

The sella turcica is surrounded by the anterior and posterior clinoid processes. The anterior clinoid processes arise from the sphenoidal lesser wings, while the posterior clinoid processes are the superolateral projections of the dorsum sellae. They serve as attachment points for the tentorium cerebelli, a membranous sheet that divides the brain.

The depressed lateral parts of the middle cranial fossa are formed by the greater wings of the sphenoid bone, and the squamous and petrous parts of the temporal bones. They support the temporal lobes of the brain. It is the site of many foramina – small holes by which vessels and nerves enter and leave the cranial cavity.

Features and contents of the middle cranial fossa

Sphenoid bone: the sphenoid bone resembles a bat having a centrally placed body with greater and lesser wings extending to both sides. The body contains the sphenoid air sinuses that are lined with mucous membrane and communicate with the nasal cavity. Like all other air sinuses of the skull, they serve as voice resonators.

Optic canal (canalis opticus): it is located anteriorly and transmits the optic nerve (n. opticus) and the ophthalmic artery (a. ophtalmica).

Superior orbital fissure. It is a slit-like opening between the lesser and the greater wings of the sphenoid bone. It transmits many important structures including the lacrimal (n. lacrimalis), frontal (n. frontalis), trochlear (n. trochlearis), oculomotor (n. oculomotorius), nasociliary (n. nasociliaris) and abducent nerves (n. abducens) as well as the superior ophthalmic artery (a. ophthalmica superior).

Foramen rotundum and foramen ovale. Foramen rotundum is situated behind the medial end of the superior orbital fissure, perforating the greater wing of the sphenoid. It transmits the maxillary nerve (n. maxillaris). Foramen ovale is situated posterolateral to foramen rotundum, also perforating the greater wing of sphenoid. It transmits both the large sensory root and the small motor root of the mandibular nerve (n. mandibularis).

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Foramen spinosum: it also perforates the greater wing of sphenoid, lying posterolateral to the foramen ovale. It transmits the middle meningeal artery (a.

meningea media) into the cranial cavity.

Foramen lacerum: it is large irregularly shaped and lies between the apex of the petrous part of the temporal bone and the sphenoid bone. The opening of this foramen is filled with cartilage and fibrous tissue and only small blood vessels pass through it.

Carotid canal (canalis caroticus): it opens into the side of the foramen lacerum above the closed inferior opening. The internal carotid artery (a. carotica interna) enters the foramen lacerum through this canal.

Impression for trigeminal ganglion (ganglion trigeminale). Lateral to the foramen lacerum, on the apex of the petrous part of the temporal bone, there is an impression for the trigeminal ganglion.

Grooves on petrous bone. On the anterior surface of the petrous bone (petrous part of temporal bone), there are two grooves for nerves. The larger medial groove is for the greater petrosal nerve (n. petrosus major) (a branch of facial nerve) and the smaller lateral groove for the lesser petrosal nerve (n. petrosus minor), (a branch of tympanic plexus).

Arcuate eminence: it is a rounded eminence found on the anterior surface of the petrous bone and is caused by the underlying superior semicircular canal.

Tegmen tympani: it is a thin plate of bone that is actually a forward extension of the petrous part of temporal bone. From behind forwards, it forms the roof of the mastoid antrum, the tympanic cavity and the auditory tube. Tegmen tympani is clinically important because it is the only barrier that separates the infection in the tympanic cavity from the temporal lobe of the cerebral hemisphere.

Median part of middle cranial fossa. The median part is formed by the body of sphenoid bone. It has the following important structures:

Sulcus chiasmatis: it lies in front and is related to the optic chiasma. It leads laterally to the optic canal on each side.

Tuberculum sellae: it is an elevation that lies posterior to sulcus chiasmatis.

Sella turcica: it is a deep depression behind the elevation (tuberculum sellae).

It lodges the pituitary gland.

Dorsum sellae: it is a square plate of bone that bounds the sella turcica posteriorly.

Posterior clinoid processes: these are two tubercles on the superior angles of the dorsum sellae. They give attachment to the fixed margin of the tentorium cerebelli.

Cavernous sinus: it is directly related to the side of the body of sphenoid bone. The oculomotor, trochlear and ophthalmic and maxillary divisions of trigeminal nerve (n. trigeminalis) pass along its lateral wall. The internal carotid artery (a. caroticus internus) and the abducens nerve (n. abducens) pass through it.

The posterior cranial fossa (fossa cranii posterior) is located above three bones: the occipital bone and two temporal bones.

It is bounded as follows: anteriorly and medially it is bounded by the dorsum sellae of the sphenoid bone. This is a large superior projection of bone that arises from the body of the sphenoid. Anteriorly and laterally it is bounded by the superior border of the petrous part of the temporal bone. Posteriorly it is bounded by the internal surface

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of the squamous part of the occipital bone. The floor consists of the mastoid part of the temporal bone and the squamous, condylar and basilar parts of the occipital bone.

The posterior cranial fossa houses the brainstem and cerebellum. The brainstem is comprised of the medulla oblogata, pons and midbrain and continues down through the foramen magnum to become the spinal cord. The cerebellum has an important role in coordination and fine motor control. Alongside the gross anatomical structures of the brainstem and cerebellum, the posterior cranial fossa also accommodates associated arteries and nerves. Some key structures will be discussed with regards to their foramina below.

Foramina. There are several bony landmarks and foramina in the posterior cranial fossa (foramen is simply a hole that allows the passage of a structure – usually a blood vessel or nerve).

The internal acoustic meatus is an oval opening in the posterior surface of the petrous part of the temporal bone. It transmits the facial nerve (n. facialis VII), vestibulocochlear nerve (n. vestibulocochlearis VIII) and labyrinthine artery (internal auditory artery).

Occipital bone. A large opening, the foramen magnum, lies centrally in the floor of the posterior cranial fossa. It is the largest foramen in the skull. It transmits the medulla of the brain, meninges, vertebral arteries, spinal accessory nerve (n.

ascendens), dural veins and anterior and posterior spinal arteries. Anteriorly an incline, known as the clivus, connects the foramen magnum with the dorsum sellae.

The jugular foramina are situated either side of the foramen magnum. Each transmits the glossopharyngeal nerve (n. glossopharyngeus), vagus nerve (n.

vagus), spinal accessory nerve (descending) (n. descendens), internal jugular vein (v.

jugularis interna), inferior petrosal sinus (sinus petrosus inferior), sigmoid sinus and meningeal branches of the ascending pharyngeal and occipital arteries (aa.

occipitales).

Directly superior to the anterolateral margin of the foramen magnum is the hypoglossal canal. It transmits the hypoglossal nerve through the occipital bone.

The cerebellar are located posterolaterally to the foramen magnum. These are bilateral depressions that house the cerebellum. They are divided medially by a ridge of bone, the internal occipital crest.

Topographic and anatomical features of the external cranial base On the skull students determine the boundary of its external base. It passes along a line wich connects protuberantia occipitalis externa with a sphenoidal rostrum (rostrum sphenoidalis) which lies between the wings of the vomer: on the superior nuchal line, through the base of the mastoid process, the posterior and lower margins of the external acoustic meatus, continues along the zygomatic process of the temporal bone, its crista infratemporalis, and on margo supraorbitalis of the frontal bone.

If you draw a line through the foramen magnum, which connects the apexes of the mastoid processes, then the external cranial base is divided into two parts:

anterior and posterior. Within the posterior part, there is occipital protuberance (condylus occipitalis) which is connected with atlas, and foramen magnum through which the medulla oblongata passes.