BIOM20002 Lecture Notes - Lecture 39: Pelvic Floor, Peristalsis, Apposition
Document Summary
Occupy cavities in the body: thorax, abdomen, pelvis. Typically tubular, with a cylindrical wall and a lumen. Mucosa (internal layer) may have folds that increase surface area for absorption. Muscularis (middle layer) contains smooth muscle that may produce waves of contraction (cid:858)peristalsis(cid:859). Serosa (external layer) covered with fluid that minimises friction. Can be continuous with a mesentery attaching viscera to body wall (eg small intestines) Provides for motility (eg peristalsis) & expansion (eg smooth muscle may be stretched without changing force of contraction to allow for storage of large volumes of liquids (bladder) or solids (rectum)) At critical point of storage (stretch) reflexes are initiated to cause micturition or defecation. Constrictions - usually at beginning & end - also at specific sites along its course (e. g. where male urethra pierces pelvic floor) A duct tends to narrow where it approaches the wall of a hollow viscus its orifice (opening) Calculi (stone) likely to lodge at orifice. e. g. gall bladder.
