HUMAN ANATOMY – VOLUME 1

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Muscles of the hypothenar

FASCIAE AND SYNOVIAL BURSAE OF THE UPPER EXTREMITY

Corresponding to topography, the fasciae of the upper extremity are named the deltoid fascia, infraspinous and supraspinous fasciae and brachial, antebrachial and hand fasciae.

The deltoid fascia (fáscia deltoídea) covers the deltoid muscle on the outside. At the front the fascia continues into the fascia of the thorax. Laterally and downward it passes into the brachial fascia. In the back the deltoid fascia accretes with the i n f r a s p i n o u s f a s c i a, which covers the infraspinous and teres minor muscles.

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The supraspinatus and infraspinatus fasciae are weakly developed. They cover the homonymous muscles and attach along the edges of the homonymous fossae of the scapula. The axillary fossa is lined by the a x i l l a r y f a s c i a (fáscia axilláris).

The brachial fascia (fáscia bráchii) encases the muscles of the arm. Its distal end continues into the antebrachial fascia. On the arm it forms intermuscular septa between separate groups of muscles. The m e d i a l i n t e r m u s c u l a r s e p t u m o f t h e a r m is relatively thick and is attached along the medial margin of the humerus. It separates the brachial and coracobrachial muscles from the medial head of the triceps. The la t - e r a l i n t e r m u s c u l a r s e p t u m o f t h e a r m separates the brachial and brachioradial muscles from the lateral head of triceps. This septum attaches along the lateral margin of the humerus. The distal ends of these intermuscular septa serve as points of origin for several forearm muscles.

The antebrachial fascia (fáscia antebráchii) is much better developed than the brachial, especially on the dorsal surface of the forearm. It forms a thick sheath around the muscles of the forearm, giving off intermuscular septa towards the bones. In the back it is attached to the posterior margin of the humerus and the olecranon process. In the proximal front region this fascia is strengthened by fibers of the b i c i p i t a l a p o n e u r o - s i s, or Piragoff’s fascia. In the region of the wrist it has a thickening, which forms the flexor and extensor retinacula. These tendon retinacula help to create optimal conditions for utilizing the force developed by muscles of the forearm. The f l e x o r r e t i n a c u l u m (r e t i n á c u l u m f l e x ó r u m) attaches to the pisiform and hamate bones medially, and the scaphoid and trapezium on the lateral. It passes over the carpal groove, turning it into the c a r p a l t u n n e l (c a n á l i s c á r p i).

The carpal tunnel contains two synovial sheaths for tendons of the flexor muscles. The c o m m o n f l e x o r s h e a t h (v a g í n a c o m m ú - n i s t e n d i n u m m u s c u l ó r u m f l e x ó r u m) confines the tendons of the superficial and deep flexors of the fingers. The t e n d i n o u s s h e a t h o f t h e f l e x o r p o l l i c i s l o n g u s (v a g í n a t é n d i n i s m . f l é x o r i s p ó l l i c i s l ó n g i) is occupied by the tendon of the homonymous muscle. This sheath extends up to the base of the distal phalanx of thumb. The common synovial flexor sheath ends at the middle of the palm, except for its lateral part, which extends up to the distal phalanx of

i t ó r u m m a n u s) have a blind beginning at the level of metacarpophalangeal joints, and extend to bases of the distal phalanges. Due to the described structure of the synovial sheaths of the hand, purulent processes spread much faster (along the sheaths) from the I and V fingers than from the others.

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The lateral and medial sections of the flexor retinaculum are separated from the rest of it, forming two small tunnels. The lateral tunnel con-

contains the ulnar nerve, artery and vein.

The extensor retinaculum (retináculum extensórum) stretches across the dorsal side, from the distal end of the radius to the styloid process of the ulna and the ulnar collateral ligament. The space beneath the retinaculum is divided by fibrous fascicles into six tunnels, which contain tendons of the extensor muscles of the wrist and fingers, and their synovial sheaths. The first tunnel, starting at the lateral edge of the retinaculum, contains tendons of the long abductor and the short extensor of thumb. The second tunnel contains tendons of the long and short radial extensors of wrist; the third contains the tendon of the long extensor of thumb; the fourth — tendons of the extensor of the fingers and extensor of the index finger; the fifth — tendon of the extensor of little finger; and the medial most tunnel contains the tendon of the ulnar extensor of the wrist. The proximal ends of these sheaths protrude 2–3 cm from underneath the retinaculum. The distal ends extend to the middle of the metacarpal bones.

The fascia of the hand (fáscia mánus) is better developed on the palmar side, where it covers the muscles of the thenar and hypothenar, tendons of the flexors of the fingers and the lumbrical muscles. Around the middle of the palm this fascia forms the palmar aponeurosis (aponeurósis palmáris). This aponeurosis has a triangular shape. Its apex is directed towards the forearm, where it serves as a point of insertion for the long palmar muscle. At the bases of the fingers this aponeurosis divides into fibrous cords, which continue onto the fingers and participate in the formation of fibrous tunnels for the tendons of the superficial and deep flexors of fingers. Fibrous fascicles of these tunnels and of the palmar aponeurosis weave into the skin, which results in the formation of characteristic grooves on the surface of the hand.

The d e e p l a m i n a o f t h e p a l m a r f a s c i a (intermuscular fascia) separates interosseous muscles of the hand from tendons of the forearm muscles. This lamina is weakly developed.

The dorsal fascia of the hand (fáscia dorsális mánus) has a superficial and a deep plate. The s u p e r f i c i a l l a m i n a is weakly developed; it stretches from the distal end of the extensor retinaculum over the tendons of the extensors. The d e e p l a m i n a is better developed. It covers the interosseous muscles and attaches to the periosteum on the dorsal surface of metacarpal bones.

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Questions for revision and examination

1.Name the muscles of the thenar, the hypothenar and the middle group of the muscles of the hand.

2.How many synovial tendon sheaths are there beneath the flexor retinaculum on the palmar side of the wrist?

3.How far does the synovial sheath of the flexors of each finger extend in the proximal direction?

4.Tendons of which muscles pass through synovial sheaths on the dorsal side of the

wrist?

TOPOGRAPHIC ANATOMY AND FATTY TISSUE SPACES

OF THE UPPER EXTREMITY

The upper extremity has several bone and muscle structures that are easily definable surfaces. These include the scapular spine, acromion, medial and lateral margins and the inferior angle of the scapula. In the subclavicular region one can palpate the coracoid process. The deltoid region, which is occupied by the large deltoid muscle, is separated from the greater pectoral muscle by the deltopectoral groove. The axillary region corresponds to the axillary fossa, which can be seen when the arm is raised. The anterior border of this fossa is the lower edge of the greater pectoral muscle, and the posterior border is the lower edge of the latissimus dorsi. On the arm there are a medial and a lateral grooves, which continue into the cubital fossa. At the sides of the elbow it is possible to palpate the medial and lateral epicondyles of the humerus. On the dorsal side of the elbow joint is the prominent olecranon process. On the anterior surface of the forearm are the r a d i a l a n d u l n a r g r o o v e s, and at the level of the radiocarpal joint it is possible to palpate the styloid processes of the ulna and radius. On the palm one can easily see the thenar and hypothenar, and between them a triangular depression. Also well definable are the creases over metacarpophalangeal and interphalangeal joints and the balls of the fingers. The dorsal surface of the hand is convex. At the base of the thumb, when it is abducted, a fossa appears between tendons of the long and short extensors. This fossa is called the anatomical snuffbox; in it lies the radial artery, which passes between the first two fingers onto the palm.

The skin on the scapular region is thick and tightly accreted with the subcutaneous tissue and the superficial fascia. The skin above the deltoid muscle is also thick and almost immovable.

In the subclavicular region the skin is thin, and the subcutaneous tissue is well developed, especially in women. The axillary region, which confines the axillary fossa, is bordered medially by the level of the third rib. Its lateral border is a line drawn on the arm between points of insertion of the

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latissimus dorsi and pectoralis major muscles. Beginning in puberty, the skin of the axillary region acquires characteristic hair growth. The skin of this region contains many sweat and sebaceous glands; the subcutaneous tissue is weakly developed. On the arm the skin is thicker on the posterior and lateral sides than on the medial; the subcutaneous tissue is loose. On the elbow joint the skin is thick on its posterior surface and thin in the front. Above the apex of the olecranon there is a subcutaneous synovial bursa. In cases of injury or prolonged compression this bursa is likely to be a site of pathological processes. On the front of the forearm the skin is thin and relatively movable, whereas on the posterior side it is thicker and has less mobility. On the palm the skin is thick and lacks hair. Its subcutaneous tissue has a cellulate structure. On the dorsal side of the hand the skin is thin and movable. The subcutaneous tissue is loose, which contributes to formation of an edema during inflammatory processes in the hand.

The subcutaneous tissue contains almost no adipose cells. The skin is attached by fibers to the proper fascia of the trapezius muscle. The fascia of the supraspinous muscle is attached at the top to the transverse ligament of the scapula, the coracoid process and the capsule of the shoulder joint. Between the supraspinous muscle and the floor of the supraspinous fossa there is a thin layer of fatty tissue, which contains the supraspinous nerve, artery and veins.

The loose connective tissue beneath the infraspinous muscle contains the circumflex artery of scapula. The supraspinous and infraspinous fascial sheaths communicate with each other near the base of the acromion (where blood vessels and nerves enter the infraspinous fossa).

The s u b d e l t o i d c o n n e c t i v e t i s s u e s p a c e continues downward until the insertion point of the deltoid muscles. This space contains the tendon of the long head of biceps brachii, branches of the axillary nerve and the posterior circumflex humeral artery.

Beneath the axillary fascia is the axillary cavity (cavum axillare), which is shaped like a pyramid, the apex of which is directed upward and medially, and the base — downward and laterally. The upper aperture of the axillary cavity is bordered by the clavicle, the first rib and the superior margin of the clavicle. This aperture connects the axillary and the cervical regions. The axillary cavity has four walls. The anterior wall is formed by the major and minor pectoral muscles; the posterior — by the latissimus dorsi, teres major and subscapular muscles; the medial wall is formed by the serratus anterior muscle; and the lateral — by the biceps brachii and the coracobrachialis muscle.

The posterior wall of the axillary cavity has two relatively large openings, which are normally covered by loose connective tissue. The t r i l a -

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t e r a l o p e n i n g is more medial, and is bordered by the subscapular muscle at the top, the teres major muscle at the bottom, and by the long head of the triceps on the lateral side. Through this opening pass the circumflex scapular artery and vein. The q u a d r i l a t e r a l o p e n i n g is more lateral; it is bordered by the surgical neck of humerus on the lateral side, the long head of the triceps on the medial side, the subscapular muscle at the top, and the major teres muscle at the bottom. This foramen serves as a passage for the posterior circumflex humeral artery and vein and the axillary nerve. The axillary cavity contains a lot of loose fibrous connective tissue rich in adipocytes, as well as blood vessels, nerves and axillary lymph nodes.

On the anterior wall of the axillary fossa there are three triangles, the borders of which define the topography of some blood vessels and nerves. The c l a v i p e c t o r a l t r i a n g l e is situated between the clavicle and the upper edge of the minor pectoral muscle. Within its boundaries lie the axillary artery and vein and the medial bundle of the brachial plexus.

The p e c t o r a l t r i a n g l e corresponds to the contours of the minor pectoral muscle. Within its boundaries lie the long thoracic nerve and the lateral thoracic artery branches off the axillary artery. Through the s u b p e c t o r a l t r i a n g l e, which is situated between the lower boundaries of the minor and greater pectoral muscles, pass the axillary artery and vein, as well as the median, musculocutaneous, ulnar and other nerves. Within this triangle the axillary artery gives off the subscapular and the anterior and posterior circumflex humoral arteries.

The neurovascular bundle, formed by the median nerve and the brachial artery and veins, passes on the arm through the medial sulcus (of the biceps muscle). On the back of the arm the proper fascia forms a sheath for the triceps muscle. In front of this sheath, through the radial canal, passes the posterior neurovascular bundle. The radial, or humeromuscular, canal (canális nérvi radiális, s. canális humeromusculáris) is situated between the posterior surface of the humerus and the triceps brachii muscle. Its upper opening (entrance) is situated at the boundary between the upper and middle thirds of the body of the humerus. At the medial side this opening is bordered by the humerus and the lateral and medial heads of triceps brachii muscle. Its lower opening (exit) is situated at the boundary between the middle and bottom thirds of humerus, between the brachialis and brachioradialis muscles. This canal serves as a passage for the radial nerve and the deep brachial artery and veins. On the back of the elbow, on either side of the olecranon process, there are two grooves. In the posterior medial cubital groove, within a tunnel, formed by the medial epicondyle, the olecranon and the fascia, lies the ulnar nerve.

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Situated on the front cubital surface is the cubital fossa (fóssa cubitális). Its bottom and upper border are formed by the brachioradialis muscle and the pronator teres. The cubital fossa contains a l a t e r a l and m e d i a l b i c i p i t a l g r o o v e s. The lateral groove is bordered by the brachioradialis muscle on the lateral side, and the brachialis muscle medially. The medial bicipital groove is situated between the pronator teres and the brachialis muscle. Situated in the subcutaneous tissue of this region are the basilic and cephalic veins. Beneath the bicipital aponeurosis pass the brachial artery and veins, and the median nerve. On the anterior cubital region there are three fascial muscle sheaths. The medial one contains the pronator teres, flexor carpi radialis, palmaris longus muscle, flexor carpi ulnaris muscles and, at the very bottom, the flexor digitorum superficialis. The lateral sheath contains the brachioradialis muscle and, beneath it, the supinator. The middle fascial sheath, which lies between the two bicipital grooves, encases the distal part of the biceps brachii and its tendon, and the anconeus muscle. In the anterior forearm region, on the antebrachial fascia there are three grooves called the radial, median and ulnar. The radial groove is situated between the brachioradialis muscle and the flexor carpi radialis. The median groove passes between the flexor carpi radialis and the flexor digitorum superficialis. The ulnar groove is bordered by the flexor digitorum superficialis and the flexor carpi ulnaris.

The antebrachial fascia gives off two intermuscular septa toward the radius, which separate the anterior, posterior and lateral fascial sheaths of the forearm. Each of these sheaths contains muscles, together with nerves and blood vessels. The largest one is the anterior fascial sheath. It contains the anterior muscles of the forearm, excluding the brachioradialis muscle, situated in four corresponding layers. Between the flexor digitorum profundus and the flexor pollicis longus there is a connective tissue space (or Pirogoff), filled by loose connective tissue. Situated beneath all the muscles, on the interosseous membrane, is a neurovascular bundle, which is formed by the anterior interosseous blood vessels and nerves.

The lateral fascial sheath contains only three muscles. More superficially lies the brachioradialis muscle, and beneath it — the extensor carpi radialis longus and extensor carpi radialis brevis muscles.

The posterior sheath contains the posterior muscles of the forearm, excluding the extensor carpi radialis longus and extensor carpi radialis brevis. Between the superficial and deep layers of muscles lies the posterior brachial connective tissue space. The posterior and anterior connective tissue spaces communicate through an opening in the interosseous membrane of forearm, which serves as a passage for interosseous vessels. Within the posterior fascial sheath, on the interosseous membrane, lies a

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neurovascular bundle, containing blood vessels and the deep branch of the radial nerve.

On the palm there are three i n t e r f a s c i a l s p a c e s, formed by two f a s c i a l s e p t a, which stretch from the superficial fascia to the III–V metacarpals. The lateral interfascial space contains the muscles of the thenar. The middle interfascial space has superficial and deep sections. Its superficial section contains tendons of the flexor digitorum superficialis and profundus, the superficial palmar arch and branches of the median and ulnar nerves. The deep section is situated between tendons of the flexors and the deep lamina of the palmar fascia. It contains the deep palmar arterial arch and its branches. The deep one communicates through the carpal tunnel with the space of Pirogoff, located on the anterior side of the forearm. The medial interfascial space contains the muscles of the hypothenar.

Questions for revision and examination

1.Name the walls of the axillary cavity. What muscles form each wall?

2.Name the triangle (and their borders) defined on the anterior wall of the axillary

cavity.

3.Where is the radial canal situated, and by what muscles formed?

4.Name the muscles situated in each fascial sheath of the forearm.

5.Describe the fasciae of the hand and their location among the adjacent muscles.

6.Name the connective tissue spaces of the upper extremity (and their locations).

MUSCLES AND FASCIAE OF THE LOWER EXTREMITY

The lower extremities serve as organs of support and movement. Due to these functions they have the most powerful musculature, which makes up more then 50 percent of the total muscle mass of the body. The muscles of the lower extremity are divided, according to their location, into the muscles of the pelvis (pelvic girdle) and muscles of the free lower extremity (of the thigh, leg and foot) (Fig. 111 and 112).

MUSCLES OF THE PELVIC GIRDLE (MUSCLES OF THE PELVIS)

Muscles of the pelvis surround the coxal joint from all sides. They have points of origin on the hipbone, lumbar vertebrae and the sacrum, and are divided into external and internal groups of muscles. The internal muscles, which are situated inside the pelvic cavity, include the iliopsoas (consists of the iliacus and the psoas major muscles), psoas minor, obturator internus, superior gemellus and inferior gemellus, and the piriformis muscles. The external muscle group consists of muscles of the sides and of the gluteal regions of the pelvis. These include the gluteus maximus,

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Fig. 111. Muscles of lower limb, right.

Anterior aspect.

1 — sartorius; 2 — iliopsoas; 3 — pectineus; 4 — abductor longus; 5 — gracilis; 6 — triceps surae; 7 — soleus; 8 — tendon of extensor hallucis longus; 9 — inferior extensor retinaculum; 10 — superior extensor retinaculum; 11 — extensor digitorum longus; 12 — fibularis brevis; 13 — tibialis anterior; 14 — fibularis longus; 15 — quadriceps femoris; 16 — tensor fasciae latae.

gluteus medius and gluteus minimus muscles, as well as the quadratus femoris muscle, the tensor of fascia lata and the obturator externus muscle.

Internal muscles of the pelvic girdle

The iliopsoas muscle (m. iliopsóas) forms part of the posterior abdominal wall. This muscle consists of two parts with two different points of origin. These are the greater psoas and the iliac muscles (see «Muscles of the posterior abdominal wall). The psoas major muscle lies in front of the quadratus femoris muscle, adjoining the anterior surface of the lumbar vertebrae. It originates from the lateral surfaces of the bodies of the vertebrae, the intervertebral disks and the transverse processes. This muscle stretches downward, crosses the pelvic brim

and unites with the iliac muscle. The iliac muscle is flattened and triangular in shape. It originates on walls of the iliac fossa of ilium, the internal lip of the iliac crest, and the iliolumbar and sacroiliac ligaments. The iliopsoas muscle passes beneath the inguinal ligament through the muscular lacuna, and is inserted into the lesser trochanter of femur.

F u n c t i o n: This muscle flexes the femur in the coxal joint. When the lower extremity is fixed, it flexes the lumbar section of the spine, bending the pelvis and trunk to the front.

I n n e r v a t i o n: lumbar plexus.

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