48. The urinary system: kidneys
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8. Skeletal system The components of the skeletal system are derived from mesenchymal elements that arise from mesoderm and neural crest. Mesenchymal cells differentiate into fibroblasts, chondroblasts, and osteoblasts, which produce connective tissue, cartilage, and bone tissue, respectively. Bone organs either develop directly in mesenchymal connective tissue (intramembranous ossification) or from preformed cartilage models (endochondral ossification). The splanch nic meso—derm gives rise
9. Muskular system Skeletal (voluntary) system.The dermomyotome further differentiates into the myo—tome and the dermatome.Cells of the myotome migrate ventrally to surround the in—traembryonic coelom and the somatic mesoderm of the ventrolateral body wall. These myoblasts elongate, become spindle—shaped, and fuse to form multinucleated muscle fibers.Myofibrils appear in the cytoplasm, and, by the third month, cross—striations appear. Individual muscle fibers increase in diameter as
28. Respiratory system The respiratory system is structurally and functionally adapt ed for the efficient transfer of gases between the ambient air and the bloodstream as well as between the bloodstream and the tissues. The major functional components of the res piratory system are: the airways, alveoli, and blood vessels of the lungs; the tissues of the chest wall and diaphragm; the systemic blood vessels; red blood cells and plasma; and respi ratory control neurons in the brainstem and
45. The digestive system: the function The digestive system, or gastrointestinal tract, begins with the mouth, where food enters the body, and ends with the anus, where solid waste material leaves the body. The primary function of the organs of the digestive system are threefold.First, complex food material which is taken into the mouth must be digested mechanically and chemically, as it travels through, the gastrointestinal tract.Second, the digested food must be absorbed by passage through
46. The digestive system: liver and stomach. Sources of energy Liver, the pancreas and the kidneys are the organs primarily engaged in the intermediary metabolism of the materials resorbed from the gasro – intestinal tract and in the excretion of metabolic waste products. Of these 3 organs the liver performs the most diverse func tions. It acts as the receiving depot and distributing center for the majority of the products of intestinal digestion and plays a major role in the intermediary
49. The urinary system: kidney vascular sypply Vascular supply begins with the renal artery, enters the kidney the hilum, and immediately divides into interlobar arteries. The arteries supply the pelvis and capsule before passing direct between the medullary pyramids to the corticomedullary junction. The interlobar arteries bend almost 90 degrees to form shoarching, arcuate arteries, which run along the corticomedullary junction. The arcuate arteries subdivide into numerous fine interlobul
50. The urinary system: ureters, uretra The calyces, renal pelves, and ureters constitute the main excretory ducts of the kidneys. The walls of these structures, in particular the renal pelvis and ureter, consist of three coats: an inner mucosa, middle muscularis, and an outer adventitia.Mucosa of the calyces and ureter is lined by a transitional epithelium, which varies in thickness with the distention of the ureter. In the collapsed state, the cells are cuboidal with larger с shaped cells