Pathophysiology II Chapter 35

GI function

provide nutrients through propulsive and mixing movements, secretion of digestive juices, and absorption of nutrients

congenital abnormalities

begin to form as early as 4th week of gestation, artesia, fistula, stenosis

atresia plus fistula

most common, abnomral connection and gap of esophagus

fistula

abnormal connection of esophagus

atresia

abnormal gap in esophagus

mouth and salivary glands

point of entry for nutrients, food broken down and moistened by salvia

esophagus

straight collapsible tube, 25 cm long, peristalic waves move food through, mucous glands are scattered throughout the submucosa

cardiac region of stomach

small area near esophageal opening

fundus

temporary food storage area, might fill with swallowed air

antrum

lower portion of stomach, no rugae

pyloric region

contains pyloric sphincter, connects stomach to duodendum

parietal cells

secrete hydrochloric acid and intrinsic factor, needed for VitB12 absorption and food digestion

G cells

secrete gastrin

chief cells

secrete pepsinogen and gastric lipase

mucous neck cells secrete

mucus

surface mucous cell

secretes mucus

small intestine

5-6 meters long

duodendum

first 22 cm of small intestine

jejunum

middle 2 meters of small intestine

ileum

forms end portion of small intestine

large intestine

1.5 metes long muscular tube that forms a frame around the small intestine

large intestine composed of

transverse colon, descending colon, sigmoid colon, rectum

skeletal muscle

upper and lower end of GI tract

smooth muscle

muscular movements performed by close layers of smooth muscle

neural control

by CNS through ANS modulated by hormonal interactions

intestinal wall controlled by

intrinsic nervous system

PNS

increases activity through vagus nerve

SNS

decreases activity through sacral segments

preganglionic neuron

cell body in brain/spinal cord, axon is myelinated fiber that extends to autonomic ganglion

postganglionic neuron

cell body lies outside the CNS in an autonomic ganglion, axon is unmyelinated fiber that terminates in a visceral effector

slow waves of GI smooth muscle

continuously present

ach spikes in GI smooth muscle

depolarization

NE spikes in GI smooth muscle

hyperpolarization

hormonal control

impulses through vagus nerve stimulate gastric secretions when taste, see, smell, or think about food

chyme

milky white sludge of gastric juices and food

large intestine function

fluid and electrolyte absorption, storage of fecal mass until expelled from body, haustal churning

defecation

takes about 18 hours to reach distal end, 1-3 mass movements per day

decreased parietal and chief cells

aging, leads to decreased HCl and pepsin in stomach causing increased pH, alkalinity

epithelial membrane changes

aging, decreased absoprtion of lipids, amino acids, glucose, Ca, Fe

decreased smooth muscle strength

aging, decreased emptying time, decreased anal sphincter tone, increased nonperitaltic waves and peristalsis