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Dissections of thoracic and abdominal hypaxial muscles

Anterior view

Thoracic and Abdominal Musculature

 1 Rectus abdominis muscle

 2 Serratus anterior muscle

 3 External intercostal muscle

 4 External oblique muscle (superficial lamina)

 5 External oblique muscle (deep lamina)

 6 Internal intercostal muscle

 7 Internal oblique muscle

 8 Innermost intercostal muscle

 9 Transversus abdominis muscle

Other Muscles and Structures

10 Platysma muscle

 11 Sternohyoid muscle

12 Sternothyroid muscle

13 Omohyoid muscle

14 Sternocleidomastoid muscle

15 Trapezius muscle

16 Deltoid muscle

17 Pectoralis major muscle

18 Anterior scalene muscle

19 Middle scalene muscle

20 Posterior scalene muscle

21 Biceps brachii muscle

22 Tensor fasciae latae muscle

23 Gluteus medius muscle

24 Gluteus minimis muscle

25 Iliopsoas muscle

26 Pectineus muscle

27 Adductor longus muscle

28 External lamina of rectus sheath

29 Linea alba

30 Tendinous intersections

31 Internal lamina of rectus sheath

32 Semilunar line

33 Arcuate line

34 Transversalis fascia

35 Inguinal ligament

36 Spermatic cord

37 Inferior epigastric vessels

38 Cutaneous nerves

Thoracic and Abdominal Hypaxial Muscles

The muscles of the thorax and abdomen develop from the hypomere of the thoracic and abdominal somites of the embryo.

Like the neck they clearly demonstrate the muscle pattern of the vertebrate body wall. The thoracic body wall differs from

the abdomen in having well-developed ribs that dominate the wall and limit the movements of the vertebral column. Because

of the well-developed segmental ribs, the muscles of the thoracic wall retain their segmental origins. The uniquely mammalian

diaphragm muscle is a member of this group that plays an important role in respiration. The outermost layer of the lateral

muscle wall is well developed in the thorax. Some portions of this muscle layer remain associated with the ribs, while the

rhomboid muscles (depicted in the upper limb chapter that follows) and large serratus anterior muscle migrate onto the

scapula to become principal stabilizers of the upper limb. The ventral ramus of each of the thoracic and upper lumbar spinal

nerves innervates these muscles.

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Dissections of thoracic and abdominal hypaxial muscles

Anteriolateral view

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Dissections of lateral muscle layers of thoracic and abdominal wall

Posterior view upper left, Lateral view upper center, Posterolateral view all others

Thoracic and Abdominal Hypaxial Muscles

Again we would have you notice the rarely described deep lamina of the external oblique muscle. Notice its continuity with

the external intercostal muscles, while the superfi cial lamina of the external oblique interdigitates with the serratus anterior

muscle. Also note the similar fi ber orientations of the intercostal muscles and their homologues in the abdominal wall.

The photos of the diaphragm on the opposite page clearly reveal the continuity of this internal layer muscle with its internal

homologue in the abdomen – the transversus abdominis muscle.

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Thoracic and Abdominal Musculature

 1 Rectus abdominis muscle

 2 Serratus anterior muscle

 3 Serratus posterior superior muscle

 4 Serratus posterior inferior muscle

 5 External intercostal muscle

 6 External oblique muscle (superficial lamina)

 7 External oblique muscle (deep lamina)

 8 Internal intercostal muscle

 9 Internal oblique muscle

10 Innermost intercostal muscle

 11 Subcostal muscle

12 Diaphragm

13 Transversus abdominis muscle

14 Quadratus lumborum muscle

15 Psoas major muscle

16 Psoas minor muscle

Other Muscles and Structures

17 Longus capitis muscle

18 Longus colli muscle

19 Splenius capitis muscle

20 Trapezius muscle

21 Deltoid muscle

22 Infraspinatus muscle

23 Teres major muscle

24 Triceps brachii muscle

25 Latissimus dorsi muscle

26 Tensor fasciae latae muscle

27 Gluteus maximus muscle

28 Gluteus medius muscle

29 Gluteus minimis muscle

30 Piriformis muscle

31 Superior gemellus muscle

32 Obturator internus muscle

33 Inferior gemellus muscle

34 Quadratus femoris muscle

35 Iliacus muscle

36 Sacrotuberous ligament

Dissection of hypaxial subvertebral muscles

Anterior view

Dissection revealing diaphragm

Superior view

Dissection revealing diaphragm

Lateral view

37 Sternum

38 Thoracic vertebra

39 Spinal cord

40 Ribs

41 Costal pleura

42 Mediastinal pleura

43 Diaphragmatic pleura

44 Parietal pericardium

45 Fibrous pericardium

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