digestive system chapt 25 Flashcards
organ system that processes food, extracts nutrients, and eliminates residue
digestive system
selective intake of food
1- ingestion
mechanical and chemical breakdown of food into a form usable by the body
2- digestion
uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph
3- absorption
absorbing water and consolidating the indigestible residue into feces
4-compaction
elimination of feces
5- defecation
five stages of digestion
1-ingestion 2-digestion 3- absorption 4-compaction 5-defecation
the physical breakdown of food into smaller particles
mechanical digestion
cutting or grinding teeth, churning action of stomach/intestines, exposes more food surface to digestive enzymes
mechanical digestion
series of hydrolysis reactions that break dietary macromolecules into their monomers (residues)
chemical digestion
some nutrients are present in a usable form in ingested food and can be directly absorbed
chemical digestion - vitamins, amino acids, minerals, cholesterol, and water
carried out by digestive enzymes produced by salivary glands, stomach, pancreas, and small intestine
chemical digestion
results of chemical digestion
polysaccharides into monosaccharides, protein into amino acids, fats into monoglycerides and fatty acids, nucleic acids into nucleotides
accessory organs:
teeth, tongue, salivary glands, liver, gallbladder, and pancreas
30 ft long muscular tube extending from mouth to anus, gastrointestinal is the stomach and intestines
digestive tract (alimentary canal)
mouth, pharynx, esophagus, stomach, small intestine, and large intestine
digestive tract (alimentary canal)
- mucosa: epithelium, lamina propria, muscularis mucosae
- submucosa
- muscularis externa: inner circular layer, outer longitudinal layer
- serosa: areolar tissue, mesothelium
digestive tract wall layers
lines the lumen (mucous membrane) (innermost)
mucosa
simple columnar in most of digestive tract, stratified squamous from mouth through esophagus, and in lower anal canal
inner epithelium of mucosa
loose connective tissue layer
lamina propria of mucosa
thin layer of smooth muscle, tenses mucosa creating grooves & ridges that enhance surface area and contact with food
muscularis mucosa of mucosa
imrpoves effieciency of digestion and nutrient absorption
muscularis mucosa of mucosa (mucous membrane)
the mucosa exhibits an abundance of lymphocytes and lymphatic nodules
mucosa-associated lymphatic tissue (MALT)m of mucosa
thicker layer of loose connective tissue; MALT extends into the submucosa in some parts of the GI tract
submucosa
contains blood vessels, lymphatic vessels, a nerve plexus, & in some places mucus-secreting gland that dump lubricating mucus into the lumen
submucosa
consists of usually two layers of muscle near the outer surface
muscularis extrerna
this layer thickens to form valves (sphincters) that regulate the passage of material through the tract
inner circular layer of musclaris externa
- outer longitudinal layer
- responsible for mobility that propels food and residue through the tract
muscularis extera
composed of thin layer of areolar tissue topped by simple squamous mesothelium
serosa
- begin in the lower esophagus
- ends just before the rectum
serosa
fibrous connective tissue layer that binds and blends the pharynx, most of the esophagus, & the rectum into adjacent connective tissue of other organs
adventitia of serosa
nervous network in esophagus, stomach, & intestines that regulates digestive tract motility, secretion, and blood flow
enteric nervous system
controls secretions of mucosa and movements of muscularis mucosae
submucosal plexus; network of enteric nervous system
parasympathetic ganglia and nerve fibers between the two layers of the muscularis externa; controls peristalsis
myenteric plexus; network of enteric nervous system
connective tissue sheets that suspend stomach and intestines from abdominal wall
mesenteries
serous membrane that lines the wall of the abdominal cavity
parietal peritoneum
ventral mesentery that extends from the lesser curvature of the stomach to the liver
lesser omentum
hangs from the greater curvature of the stomach (its left margin)
greater omentum
extension of the mesentery that anchors the colon to the abdominal wall
mesocolon
when an organ is enclosed by mesentery on both sides “within peritoneal cavity”
intraperitoneal
organs enclosed by mesentery on both sides:
stomach, liver, parts of small and large intestine
“outside peritoneal cavity” when an organ lies against the posterior body wall and is covered by peritoneum on its anterior side only
retroperitoneal
organs that lie against posterior body wall and is covered by peritoneum on its anterior side only
duodenum, pancreas, and parts of large intestine
loosely suspended from abdominal wall by mesenteries
digestive tract
serous membrane that lines wall of abdominal cavity and form mesenteries
parietal peritoneum
site for ingestion (food intake), taste, chewing and chemical digestion, swallowing, speech, and respiration
mouth (oral, buccal cavity)
anterior opening between lips
oral fissure
posterior opening to the throat
fauces
what lines the mouth
stratified squamous epithelium
the mouth is keratinized in these areas
gum and hard palate
mouth is nonkeratinized in these areas
floor of mouth, soft palate, and inside of cheeks and lips
median fold that attaches each lip to the gum between the anterior incisors
labial frenulum
space between cheeks or lips and the teeth
vestibule
retain food and pushes it between teeth, essential for speech, sucking and blowing
cheeks and lips
colors like the rest of the face, has hair follicles and sebaceous glands
cutaneous area of lip
hairless region where lips meet, redder and more sensitive than cutaneous area
red (vermillion) area
inner surface of the lips facing the gums and teeth
labial mucosa
muscular, bulky, agile and sensitive organ
tongue
manipulates food between teeth, senses taste and texture, covered by nonkeratinized stratified squamous epithelium
tongue
bumps and projection that are the sites of most taste buds
lingual papillae
anterior two thirds of tongue; it occupies oral cavity
body of tongue
posterior one-third of the tongue; occupies the oropharynx
ROOT OF TONGUE
a V-shaped row of papillae that marks the boundary between the body and root of tongue
vallate papillae
groove behind vallate papillae of tongue
terminal sulcus of tongue
median fold that attaches the body of the tongue to the floor of the mouth
lingual frenulum of tongue
contained entirely within the tongue; produces subtle tongue movements of speech
intrinsic muscles of tongue
with attachments outside in the tongue; produce stronger movements of food manipulation
extrinsic muscles of tongue
genioglossus, hyoglossus, palatoglossus, and styloglossus are what
extrinsic muscles of tongue
serous and mucous glands amid the extrinsic muscles that secrete a portion of the saliva
lingual gland of tongue
contained in the root of the tongue
lingual tonsils
separates oral cavity from nasal cavity; makes it possible to breathe while chewing food
palate
anterior portion thats supported by the palatine processes of the maxillae and the palatine bones
hard (bony) palate
transverse ridges that help the tongue hold and manipulate food
palatine rugae of hard palate
posterior to hard palate with more spongy texture
soft palate
no bone, composed of skeletal muscle and glandular tissue
soft palate
conical medical projection visible at the rear of the mouth; helps retain food in the mouth until ready to swallow
uvula in soft palate
where are palatine tonsils located
wall between muscular arches on each side of oral cavity
palatoglossal arch (muscular arch)
anterior arch of oral cavity
palatopharyngeal arch (muscular arch)
posterior arch of oral cavity
the teeth are called what
dentition
how many adult teeth
32 adult teeth
- 16 in mandible (lower jaw)
- 16 in maxilla (upper jaw)
chisel-like cutting teeth used to bite off a piece of food
2 incisors
pointed and act to puncture and shred food
1 canine
broad surface for crushing, shredding, grinding
2 premolars
even broader surface for crushing, shredding, and grinding
3 molars
tooth socket in bone
alveolus in teeeth
joint formed between tooth and bone
gomphosis
modified periosteum whose collagen fibers penetrate into the bone on one side and into the tooth on the other
periodontal ligament
covers the whole alveolar bone
giniva (gum)
portion above the gum in mouth
crown
portion below the gum, embedded in alveolar bone
root
point where crown, root, and gum meet
neck
space between the tooth and the gum
gingival sulcus
hard yellowish tissue that makes up most of the tooth
dentin
covers crown and neck; non cellular secretion that cannot regenerate
enamel
covers root in mouth
cement
space in a root leading to pulp cavity in the crown
root canal
pore at the basal end of each root canal
apical foramen
meeting of the teeth with the mouth closed
occlusion
develop beneath gums and erupt in a predictable order
teeth
calcified plaque
calculus
sticky residue on teeth made up of bacteria and sugars
plaque
breaks food into smaller pieces to be swallowed and exposes more surface to digestive enzymes
mastication (chewing)
functions of saliva
moistens mouth, begins starch and fat digestion, cleanses teeth, inhibits bacterial growth, dissolves molecules, moistens food
hypotonic solution of 97 to 99.5% water and electrolytes, phosphate, and bicarbonate
saliva
stimulates saliva glands to produce an abundance of thin, enzyme-rich saliva
parasympathetic fibers
produces less abundant saliva and more mucous
sympathetic activity
muscular funnel connecting oral cavity to esophagus and nasal cavity to larynx
pharynx
food pauses here because of constriction
lower esophagus sphincter
complex action involving over 22 muscles in the mouth, pharynx, and esophagus
swallowing
pair of nuclei in MEDULLA OBLONGATA that coordinates swallowing
swallowing center
swallowing under voluntary control
oral phase
involuntary swallowing
pharyngeal phase
small area in stomach within 3 cm of the cardial orifice
cardial part (cardia)
dome-shaped portion superior to esophageal attachment in stomach
fundus
makes up greatest part of stomach
body
narrower pouch at the inferior end of stomach
pyloric part
margins of stomach
curvatures
lesser omentum connects lesser curvature of stomach to what
liver
stomach receives what
- parasympathetic fibers from vagus
- sympathetic fibers from celiac ganglia
blood drained from stomach and intestines enters ___ circulation and is filtered through livers before returning to heart
hepatic portal
has a simple columnar epithelium covered by mucous
stomach
apical region of stomach is filled with
mucin
swells with water and becomes mucus after it is secreted
mucin
depressions in gastric mucosa
gastric pits
found in base of pit and in neck of gland, divide rapidly and produce continual supply of new cells to replace cells that die
regenerative (stem) cells
found most in the upper half of the stomach gland, secretes hydrochloric acid, intrinsic factor, and ghrelin
parietal cells
most numerous cells in stomach
chief cells
2 to 3 L per day produced by the gastric glands, mainly a mixture of water, hydrochloric acid, and pepsin
gastric juice
produced by chief cells, digests 10 to 15% of dietary fats in stomach
gastric lipase
a glycoprotein secreted by parietal cells, essential to absorption of vitamin by the smll intestine
intrinsic factor
needed to synthesize hemoglobin
vitamin
gastric and pyloric glands have a variety of cells that produce a variety of
chemical messengers
secreted by parasympathetic nerve fibers of both reflexes
acetylcholine
paracrine secretion from enteroendocrine cells in the gastric glands
histamine
hormone produced by enteroendocrine G cells in pyloric gland
gastrin
reddish-brown gland located immediately inferior to the diaphragm; bodies largest gland
liver
secretes bile which contributes to digestion
liver
four lobes of the liver
right, left, quadrate, and caudate
__ __ separates right and left lobes of liver
falciform ligament
fibrous remnant of umbilical vein in liver
round ligament
irregular opening between quadrate and caudate lobes in liver
hilum
point of entry for hepatic portal vein and exit for bile passages
hilum
adheres to a depression on the inferior surface of the liver, between right and quadrate lobes
gallbladder
tiny cylinders that fill the interior of the liver
hepatic lobules
blood filled channels that fill spaces between the plates, lines by fenestrated endothelium
hepatic sinusoids
allows plasma into the space between hepatocytes from blood cells
hepatic sinusoids
__ are separated by a sparse connective tissue called stroma
hepatic lobules
filtered through sinusoids, then collected into the central vein
blood
flows into right and left hepatic veins, drains into the inferior vena cava
blood
narrow channels into which the liver secretes bile
bile canaliculi
descends through lesser omentum toward the duodenum
bile duct
pear shaped sac on underside of liver
gallbladder
serves to store and concentrate bile by absorbing water and electrolytes
gallbladder
internally lined by highly folded mucosa with simple columnar epithelium
gallbladder
yellow-green fluid containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids
bile
principal pigment derived from the decomposition of hemoglobin
bilirubin
steroids synthesized from cholesterol
bile acids (bile salts)
forms if bile becomes excessively concentrated with wastes
gallstones
hard mases in either the gallbladder or bile ducts
gallstones
how does bile get to the gallbladder
filling the bile duct then overflowing into the gallbladder
how much bile does the liver secrete daily
500 to 1000 mL
80% of bile acids are reabsorbed in the __ and returned to liver
ileum
20% of the bile acids are excreted in the
feces
gallstones are composed of
cholesterol, calcium carbonate, and bilirubin
use of ultrasonic vibration to pulverize gallstones without surgery
lithotripsy
spongy retroperitoneal gland posterior to greater curvature of stomach
pancreas
has a head encircled by duodenum, a body, and a tail on the left
pancreas
pancreatic islets that secrete insulin and glucagon; concentrated in the tail of the gland
endocrine portion on pancreas
99% of pancreas that secretes 1200 to 1500 mL of pancreatic juice per day
exocrine portion of pancreas
alkaline mixture of water, enzymes, zymogens, sodium bicarbonate, and other elctrolytes
pancreatic juice
ducts secrete
bicarbonate
digests starch
pancreatic amylase
digests fat
pancreatic lipase
3 stimuli are responsible for the release of pancreatic juice and bile
acetylcholine, cholecystokinin, secretin
stimulates pancreatic secretion
acetylcholine
stimulates pancreas to release enzymes, contracts gallbladder, relaxes ampulla sphincter
cholecystokinin
stimulates liver and pancreas to secrete sodium bicarbonate
secretin
longest part of the digestive tract, nearly all chemical digestion and nutrient absorption occurs here
small intestine
small intestine is divided into 3 regions
duodenum, jejunum, ileum
receives stomach contents, pancreatic juice, and bile; stomach acid is neutralized here
duodenum
thick wall with rich blood supply; most digestion and nutrient absorption occurs here
jejunum
last 60% of small intestine, thinner wall, less vascular, paler pink color.
ileum
both __ and __ are intraperitoneal and covered with serosa
jejunum and ileum
makes mucosa look fuzzy, core filled with areolar tissue of lamina propria
villi
forms a fuzzy brush border on apical surface of each absorptive cell
microvilli
numerous pores that open into tubular glands on the floor of the small intestine between bases of the villi
intestinal crypts
intestinal crypts secretes __ of intestinal juice per day
1 to 2 L
secretes bicarbonate-rich mucus which neutralizes stomach acid and shield the mucosa from it
duodenal gland
types of movement that occur in the small intestine
segmentation and peristalsis
movement where ring-like constrictions appear in several places along the intestine and then relax as new constrictions form elsewhere
segmentation movement in small intestine
waves of contraction in small intestine that moves chyme toward colon
peristalsis movement in small intestine
digestion begins in the mouth by salivary amylase, then digestion continues into small intestine with pancreatic amylase and other enzymes
carbohydrate digestion
broken into smaller peptides in stomach by pepsin, then broken into dipeptides in small intestine via other enzymes, then free amino acids moving into epithelium
protein digestion
stomach lingual lipase breaks down to free fatty acids, small intestine pancreatic lipase breaks to monoglycerides and free fatty acids, then micelles brought into epithelium to break into triglycerides, to then flow into the lacteal
fat digestion
fat soluble vitamins absorbed with lipids. water soluble vitamins absorbed by simple diffusion
vitamin and mineral digestion
small intestine absorbs most water consumed via osmosis
water digestion
absorbed by carrier-mediated transport across absorptive cell surface
how carbohydrates and proteins are absorbed by small intetsine
lipids leave micelles at brush border to diffuse into absorptive epithelial cells and ultimately flow into lacteal
how fat is absorbed by small intestine
