From inside (lumen) to the outer surface of organs in order: mucosa, submucosa, muscularis externa, serousmembrane
Serosa is a serous membrane with simplesquamousepithelium and looseconnectivetissue
Visceral peritoneum is on the surface of much of the gastrointestinaltract
Adventitia: loose CT
Mucosa: laminapropria (loose CT containing lymphatics and immunesystemcells), muscularismucosae (thin layer of CT), for secretion and absorption
Muscularis externa: mostly smoothmuscle cells, innercircular and outer longitudina
Intraperitoneal organs are not really in the peritonealcavity, they have visceralperitoneum on most of the surface and are connected to abdominal wall by a mesentery, (anchored to the posterior abdominal wall)
Retroperitoneal are posterior to peritoneum and may have visceralperitoneum on one or more surfaces
Mesentery is a double layer of serousmembrane, with connective tissue and neurovascular structures between
pharynx parts
nasopharynx, oropharynx, laryngopharynx
swallowing Involves muscular contraction called peristalsis: wave of relaxation and contraction of pharyngeal and oesophagus muscles
HCl results in chyme having a low pH (2-3), it is antibacterial and denatures protein
enzymes in stomach
pepsinogen (into pepsin in lumen and begins proteindigestion) and gastriclipase (continues lipiddigestion)
stomach releases mucous (to protect epithelium from acidic chyme) and also releases intrinsicfactor, needed for the absorption of VitaminB12 in the intestine
small intestine from top to bottom
duodenum, jejunum, ileum
small intestine Has smooth muscle contraction: segmentation which mixes contents and peristalsis which moves contents along length
small intestine secretions
Secretions include intestinal cell enzymes (peptidases, disaccharidases, nucleosidases) and water, ions, and mucus
Chemical digestion in SI occurs in two phases: in lumen and at brush border
chemical digestion in SI lumen
enzymes from pancreas break covalentbonds in macromolecules to form smaller macromolecules
chemical digestion in small intestine at brush border
the intestinal epithelial cell enzymes complete digestion process prior to absorption
Absorption in the small intestine includes nutrients, water, and ions by: simplediffusion, facilitateddiffusion, secondaryactivetransport (relies on Na+ electrochemical gradient), or active transport.
Nutrients can be absorbed by enterocytes in digestive tract, then to the blood capillaries in villi, to venules, to veins
Bile: exocrine secretion produced by liver, stored, and concentrated in gallbladder
bile and pancreatic juice are both released into duodenum when food enters the stomach and duodenum
Bile salts (amphipathic) aids digestion and absorption of fat by emulsifyingfats, and solubilising the digestion products (increases surface area)
Fats and fat-soluble vitamins to the lymphatic system:
fattyacids,glycerol, and monoglycerides are absorbed and reynthesised into triglycerides in enterocytes, packaged into chylomicrons, travel to lymphcapillaires, lymphnodes, thoracicduct, left subclavian vein, around body
Segmentation in small intestine: alternating of contraction and relaxation to move contents
small intestine secretions
intestinal cell enzymes attached to microvilli (peptidases, disaccharide-ases, nucleosidases), water, ions, and mucus
hepatic portal venous system
Venousblood from the gut, containing absorbednutrients goes to hepaticportalvein, This blood flows through the liver, hepatic vein, inferiorvenacava, and then the rightatrium
enteric nervous system regulation
sensory, motor, and inter-neurons within ganglia in walls of GIT, local control of motility and secretion in response to conditions in the lumen of the gut
endocrine regulation
Enteroendocrine cells (distant effects) and paracrine cells (local effects), Contribute to control of motility (smoothmuscle) and secretion