Chapter 25: Digestive System

Alimentary canal

which organ group Digests and absorbs food

Teeth, tongue, gallbladder

Accessory digestive organs

Mechanical digestion

physical breakdown of food

into smaller particles

Chemical digestion

series of hydrolysis reactions

that break macromolecules into their monomers

Enteric nervous system

a nervous network in the

esophagus, stomach, and intestines that regulated digestive

tract motility, secretion, and blood flow

in submucosa

Submucosal (Meissner) plexus is

parasympathetic

Myenteric (Auerbach) plexus is

Mesenteries

connective tissue sheets that loosely suspend

the stomach and intestines from the abdominal wall

Parietal peritoneum

a serous membrane that lines the

wall of the abdominal cavity

lines the organs

what does Visceral peritoneum do?

Mesocolon

extension of the mesentery that anchors the colon to the posterior abdominal wall

Intraperitoneal

when an organ is enclosed by mesentery on both sides

Retroperitoneal

when an organ lies against the posterior body wall and is covered by peritoneum on its anterior side only

Lesser omentum

attaches stomach to liver

Greater omentum

covers small intestines like an apron, hangs from the greater curvature of

the stomach

Neural, Hormonal, Paracrine mechanisms

Motility and secretion of the digestive tract are

controlled by three mechanisms

Short (myenteric) reflexes:

stretch or chemical stimulation acts through myenteric plexus

Long (vagovagal) reflexes:

parasympathetic stimulation of digestive motility and secretion

Oral (buccal) cavity

Bounded by lips, cheeks, palate, and tongue

Vestibule:

recess internal to lips and cheeks, external to teeth and gums

Oral cavity

proper lies within the teeth and gums

Labial frenulum

median attachment of each lip to the gum

Lingual lipase

digests fat after reaches the stomach

Lysozyme

enzyme that kills bacteria

Immunoglobulin A

inhibits bacterial growth

Electrolytes

Na+, K+, Cl-, phosphate & bicarbonate

Parasympathetic stimulation

salivary glands produce thin saliva, rich in enzymes

Sympathetic stimulation

produce less abundant, thicker saliva, with more mucus

Pharynx:

Allow passage of food, fluids, and air

Esophagus:

Flat muscular tube from laryngopharynx to stomach

Segmentation

•movement in which stationary ringlike constrictions appear in several places along the intestine

Salivary amylase

begins starch digestion, stops working in acidic stomach (if < 4.5

Pancreatic enzymes

take over protein digestion by

hydrolyzing polypeptides into shorter oligopeptides

monosaccharides

Polysaccharides into

amino acids

Proteins into

glycerol and fatty acids

Fats into

nucleotides

Nucleic acids into

mucus

Mucous neck cells: secrete

HCl and.Intrinsic factor

Parietal cells secrete:

pepsinogen–Inactive enzyme

Chief cells: secrete

hormones & paracrine messengers

Enteroendocrine cells: secrete