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Anatomy Atlases: Atlas of Human Anatomy in Cross Section: Section 5. Lower Thorax (Lungs) and Abdomen

Atlas of Human Anatomy in Cross Section: Section 5. Lower Thorax (Lungs) and Abdomen

Plate 5.13

Ronald A. Bergman, Ph.D., Adel K. Afifi, M.D., Jean J. Jew, M.D., and Paul C. Reimann, B.S.
Peer Review Status: Externally Peer Reviewed

Plate 5.13

Upper Left Quadrant

Lower Left Quadrant

Lower Right Quadrant

Upper Right Quadrant

1. Lumbar Iymph nodes
2. Transverse colon
3. Inferior epigastric a. and v.
4. Inferior vena cava
5. Testicular a. and v.
6. Ileum
7. Transversus abdominis m.
8. Internal abdominal oblique m.
9. External abdominal oblique m.
10. Ureter

11. Right colic a. and w.
12. Liver
13. Ascending colon
14. Subperitoneal fat
15. Peritoneum
16. Latissimus dorsi and quadratus lumborum mm.
17. Psoas major and anulus fibrosus of intervertebral disk
18. Intertransversarius m.
19. Second and third lumbar nerves
20. Nucleus pulposus, intervertebral disk, L3/L4
21. Thoracolumbar fascia, longissimus m.
22. Thecal sac, filum terminale, and cauda equina
23. Ligamentum flavum
24. Spinous process, L3

25. Multifidus m.
26. Aponeurosis of origin, erector spinae m.
27. Superior articular process, L4
28. Third lumbar nerve
29. Erector spinae and iliocostalis lumborum mm.
30. Second lumbar nerve
31. Abdominal obliques and transversus abdominis origin: thoracolumbar fascia and lumbar triangle
32. Quadratus lumborum m.
33. Psoas major m.
34. Jejunum
35. Descending colon
36. Intercostal nerve
37. Genitofemoral nerve
38. Ureter

39. Gonadal a. and v.
40. Jejunal aa.
41. Lumbar Iymph node
42. Ileum
43. Transverse colon
44. Inferior mesenteric a.
45. Superior mesenteric aa., brs.
46. Aortic plexus of nerves
47. Abdominal aorta
48. Rectus abdominis m.
49. Ligamentum teres, hepatis
50. Linea alba

This section passes through the third lumbar intervertebral disk, where one may see the nucleus pulposus (20) and the anulus fibrosus (17). The spinous process of L3 (24) and the superior articular process of L4 (27) are also seen.

The three abdominal wall muscles-transversus abdominis (7), internal oblique (8), and external oblique (9)-are well developed in this cut. Between the internal and external oblique an intercostal, possibly T11, nerve can be found.

On the left side, the sacculations of the transverse colon (43), sections of ileum (42), appear, and the descending colon (35) is found in its usual left lower lateral position on the posterior abdominal wall. A few sections of jejunum (34) still remain at this level. The latissimus dorsi muscle is already aponeurotic and medial and does not appear on the left side. The thoracolumbar fascia (31) provides one point of origin of the abdominal oblique and transversus abdominis muscles. This area, devoid of an external covering of muscle, is known as the lumbar triangle (31).

In the middle of the section, an internal view of the colon (in general) reveals a smooth surface because the mucosal glands form pits and project downward rather than having luminal projections such as mucosal folds and villi, as is the case for the small intestine. The differentiation between the small bowel and the large bowel is usually readily made. Various primary and secondary branches of the abdominal aorta (47) are seen: gonadal (39), jejunal (40), inferior mesenteric (44), and right colic (11) arteries. The inferior vena cava (4) is adjacent to the aorta.

On the right side, the transverse colon (2) sacculations and the ascending colon (13) (which appears three sided) are seen. The three sided appearance is due to the restraining effect of the three tenia coli, bands of smooth muscle formed of the outer longitudinal layer of the tunica muscularis of the colon. The right lobe of the liver (12) is occupying a progressively smaller part of the right side of the abdomen. The peritoneum (15) is clearly marked on the right side separating the abdominal cavity from the subperitoneal fatty layer (14). Note the small intertransversarius muscle (18) beneath psoas major (17) and quadratus lumborum (16).

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