Digestive System Slides Flashcards
Peritoneum:
lines coelom;
covers organs
Mesentery:
peritoneal extension
provides support; vessels draw
nutrients from canal
Extramural gland;
e.g.
salivary; pancreas
Mucosa
Epithelia mostly simple columnar
or stratified squamous.
Lamina propria with lots of WBCs
Mucosal pits
Some are glands e.g. gastric pits.
Also sanctuaries for mitosis.
Muscularis
Inner circular layer; outer longitudinal
Causes “gut motility” e.g. Peristalsis:
wave of contraction drives digesta
analward as a bolus
Oral Cavity
Tongue manipulates food
Salivary glands make saliva:
Lubrication
Digestive enzymes
Modified as reptile venom glands
Teeth typical
Keratin Teeth or equivalent
Epithelial outgrowths; are composed of keratinocytes
Agnatha
Baleen in whales
Most vertebrates have bony teeth
Ectoderm derivatives develop in connective tissue
Outer layer of human teeth
Pure hydroxyapatite.
Hardest substance in the body.
Made by cells called Ameloblasts.
Inner layer of human teeth
Bonelike matrix.
Made by cells called Odontoblasts.
Tooth held in place by
“Periodontal Ligament” of
dense connective tissue
Pulp Cavity
Vascular and innervated.
Lined with Odontoblasts
Odontoblasts
Monitor dentin condition;
make 2o dentin to accommodate wear
Esophagus Parts and pieces
Peristalsis of swallowing
muscularis transition
skeletal muscle to smooth muscle
abundant mucus glands
Esophagus adaptations
Crop in birds dilated portion; stores food Rumen in “Foregut Fermenters” e.g. Cattle houses microbes to digest cellulose
Stomach parts and functions
Stores food; begins protein digestion
Rugae: inner folds permit stretch
3 layered muscularis for mixing motions
Gastric pits secrete “gastric juice”
Gastric juice includes:
Hydrochloric acid
Digests; protects against parasites
Proteases: enzymes that break down proteins
Mucus: keeps stomach from digesting self
Birds have two stomachs:
Glandular stomach: secretes juice Gizzard: grinding stomach Mucosa covered with hard keratin-like protein Some birds swallow small rocks to help grind food
The vertebrate stomach produces an
acidic product called
Chyme
Chyme moves into the Duodenum, the
beginning of the small intestine
Duodenum receives:
Chyme from the stomach
Digestive enzymes from the pancreas
Bile from the liver
Duodenum wall has Brunner’s glands:
secrete alkaline mucus to neutralize chyme
Small Intestine parts and functions
Lined with columnar Enterocytes Enterocytes have apical “brush border” enzymes that finish digestion Enterocytes perform all absorption Enterocyte surface area is maximized
How enterocyte surface is maximized
Great intestinal length Spiral valve in some fishes e.g. sharks ~Circular internal folds ~Villi: finger-like mucosa projections ~Microvilli of enterocytes
These ~ increase SA by 600X`
