Chapter 25 Digestive System

digestive system

Organ system processes food

digestive tract

Tube runs from mouth to anus

five functions of digestive system

Ingestion, digestion, absorption, compaction, defecation.

ingestion

Selective intake of food

digestion

Mechanical and chemical breakdown of food

absorption

Uptake of nutrient molecules

compaction

Absorbing water and consolidating indigestible residue

defecation

Elimination of feces

mechanical digestion

physical breakdown of food into smaller particles

chemical digestion

series of hydrolysis reaction breaks into monomers

monomers of polysaccharides

Monosaccharides.

monomers of proteins

Amino acids

monomers of fats

Monoglycerides and fatty acids

monomers of nucleic acids

Nucleotides

four layers of digestive tract

Mucosa, submucosa, muscularis externa, serosa.

function of mucosa layer

Secretes mucus

function of submucosa layer

Contains blood vessels lymphatic ducts.

function of muscularis externa layer

Moves food through canal peristalsis and segmentation

two types of muscles in muscularis externa

Circular longitudinal muscles

third muscle of stomach

Oblique muscle

circular muscles thicken form

Sphincters

another name for digestive system

Digestive Tract

serous membrane surrounding abdominopelvic organs

Peritoneum

function of enteric nervous system

Coordinates digestive system activity

enteric nervous system also known as

Gut Brain

two networks of neurons in enteric nervous system

Submucosal plexus Myenteric plexus

submucosal plexus controls

Glandular secretions of mucosa and movements of muscularis mucosae

myenteric plexus controls

Peristalsis and muscularis externa

mesenteries

Connective tissue sheets suspends stomach

ventral mesentery lesser curvature of stomach to liver

Lesser omentum

greater curvature of stomach cover small intestine

Greater omentum

functions of mouth

sensory responses to food, chewing

type of epithelium lines mouth

Stratified squamous epithelium

covers surface of tongue

Nonkeratinized stratified squamous epithelium

function of tongue

Manipulates food between teeth

bumps and projections on the tongue

Lingual papillae

role of lingual papillae

Sites of most taste buds

Vallate papillae

V

Palate

Roof of mouth

Hard palate

Bony surface for mashing food

Soft palate

Muscle closes off nasopharynx

Uvula

Conical projection at back of mouth

Deciduous teeth

Baby teeth (6

Permanent teeth

Adult teeth (6

Wisdom teeth

Third molars (17

Incisors

Front teeth for cutting

Canines

Pointed teeth for tearing

Premolars

Bicuspids for grinding

Molars

Large teeth for grinding

Crown

Visible part of tooth above gum

Root

Part of tooth below gum

Neck

Point where crown, root, and gum meet

Gingival sulcus

Space between tooth and gum

Periodontal ligament

Anchors tooth in socket

Dentin

Hard tissue that makes up most of tooth

Enamel

Noncellular covering of crown

Cementum

Covering of root

Another name for chewing

mastication

Mastication

breaking food into smaller pieces to be swallowed

What manipulate food

tongue, buccinator, orbicularis oris

elevates lower teeth to crush food

masseter and temporalis

functions of salivary glands

Moistens mouth, begins starch

What triggers salivation

Presence of food, tactile, pressure

function of pharynx

Connects oral cavity to esophagus

three phases of swallowing

Oral phase, pharyngeal phase, esophageal phase

during oral phase of swallowing

Voluntary control, tongue forms bolus

during pharyngeal phase of swallowing

Involuntary, soft palate rises, larynx moves upward

during esophageal phase of swallowing?

Involuntary, bolus moves in esophagus, peristalsis

function of upper esophageal sphincter

Prevents air from entering

esophagus pass through diaphragm

Esophageal hiatus

composition of esophagus

Nonkeratinized stratified squamous epithelium

four regions of stomach

Pyloric, Fundus, Cardial, Body

function of stomach

Food storage and mechanical chemical digestion

chyme

soupy or pasty mixture of food in stomach

role of mucosa in stomach

folded up forms rugae secretes mucus

pyloric sphincter

joins the distal end of stomach with small intestine

stomach protected from digesting itself

protective mucosal barrier

three layers of the muscularis externa in stomach

Outer longitudinal, middle circular, and inner oblique layers

cells found in gastric glands of stomach

Parietal cells, chief cells, mucous cells

parietal cells secrete

Hydrochloric acid (HCl), intrinsic factor

HCl important in stomach

activate pepsin, denature proteins, kills bacteria

role of intrinsic factor

B12 absorption

HCl produced in stomach

Carbonic acid parietal cells pumped into gastric gland lumen

cell found in cardiac region of stomach

Cardiac glands

cell found in pyloric region of stomach

Pyloric glands

cell found in body region of stomach

Gastric glands

chief cells secrete

Pepsinogen and gastric lipase.

activates pepsinogen

Exposure to HCl or preexisting pepsin molecules.

enteroendocrine cells found

Stomach glands.

enteroendocrine cells release

Hormones into lamina propia.

three phases of gastric activity

Cephalic phase, gastric phase, intestinal phase.

happens in cephalic phase

Stomach is controlled by brain.

triggers the cephalic phase

Stimuli

How much stomach's acid secretion occurs in cephalic phase?

40%.

happens in gastric phase

Stomach controls itself.

parietal cells to increase HCl output in gastric phase

Stretch receptors in stomach.

G cells to secrete gastrin in gastric phase?

Chemical stimuli

gastrin target in gastric phase

Parietal cells to increase HCl production.

happens in intestinal phase

Stomach is controlled by small intestine.

activates enterogastric reflex in intestinal phase

Chyme entering duodenum