Principles of viscera and body cavities

===Lecture Details===
Norm Eizenberg; Week 1 MED1011; Anatomy
===Lecture Content===
Layers of wall in hollow viscera are mucosa, muscularis and serosa. There are normal constrictions of the lumen which are generally at the beginning and end of a tubular viscus. Visceral obstruction can be internal, intramural (in the wall) or extraluminal. A duct opening into the lumen of a hollow viscus tends to narrow as it traverses the wall. Endocrine glands have a rich blood supply and secretions are routed directly to bloodstream. Paired viscera recieves a unilateral neurovascular supply and refers pain to the same side. Midline organs recieve paired bundles. Unpaired viscera, even non-midline, recieve a bilateral nerve supply, pain is felt over the midline. Serous membranes for mesentaries for unpaired viscera. It enables mobility and allows artery and nerve supply. Retroperitoneal viscera are the duodenum, ascending and descending colon and rectum. Kidneys are peritoneal viscera, and bladder, vagina and rectum are subperitoneal. Involuntary and voluntary sphincters recieve variable nerve supplies. Muscular functional sphincters occur as a consequence of anatomical placement, for example as the ureters travel through the bladder wall. Mucosal functional sphincters eg the gall bladder is where the mucosa is so complex that it is impossible for substances to travel through it freely (cystic duct).
Epithelial lining of tissues is avascular, underlying connective tissue is highly vascular. Junctions between tissues can be horizontal or vertical. Epithelial interfaces occur where epithelium/lamina propria/smooth muscle meets epidermis/dermis/skeletal muscle. Mucocutaneous junctions are where arterial anastomoses, watershed areas of lymph drainage and internervous lines occur. Smooth muscle sphincters are supplied by visceral nerves and skeletal muscle sphincters by somatic nerves.
Transmucosal junctions are usually where territories of different developmental origin meet (foregut, midgut, hindgut). Lines for reflexes particularly occur where mucosa overlies skeletal muscle.
Visceral pain lines are thoracic and pelvic pain lines. Thoracic is between T4 and L1, pelvic is S2 to S4. There tends to be no anastomoses over vascular segments although there may be some venous communication. Splanchic is also known as visceral mesoderm, and splanchic nerves supply viscera. The body wall and its serous membrane are supplied by somatic nerves, the gut and its mucosa are supplied by visceral nerves. Some vascular supply can be 'public' or 'private' as in the bronchial supply of arteries compared to the pulmonary supply for gas exchange.
Layers of the body wall are skin, subcutaneous tissue, 3 layers of muscle, fascial layer, extraperitoneal fat and the parietal peritoneum. A hernia is an abnormal protrusion through an avenue. Can be of disc or viscus. Mesothelium surrounds the layer opposite to the epithelium of tissues (peritoneal layer).
Prolapse means falling.
===Readings===
====Eizenberg: Ch 8 and 16====