Chapter 24: The Digestive System Flashcards
The __________ is long tube that is open at both ends
for the transit of food during processing
Named portions of the tube include the
esophagus, stomach, small intestine, large
intestine, and rectum
Gastrointestinal (GI) Tract
_________ are not part of the GI tract,
but they do contribute to food processing
Accessory structures include the teeth,
tongue, salivary glands, liver, gall bladder,
and pancreas
Accessory structures
Submucosal plexus
Myenteric plexus
Enteric Nervous System
Autonomic Nervous System
Parasympathetic
Sympathetic
___________ regulate GI secretion and
motility in response to stimuli within the GI tract
GI reflex pathways
The _________ is the largest serous membrane
in the body
peritoneum
The ______ is formed by the cheeks, hard and soft
palates, and tongue
mouth
_____________ lie outside the mouth and empty
their contents into ducts which deliver saliva into the
oral cavity
Salivary glands
3 pairs:
Parotid
Submandibular
Sublingual
The ______, together with associated muscle,
forms the floor of the oral cavity
Composed of skeletal muscle covered with mucous
membrane
Participates in chewing, swallowing, and speech
The upper and lateral surfaces of the tongue are
covered with papillae, some of which contain taste
buds
TONGUE
The _____ project into the mouth and are adapted
for mechanical digestion
teeth
Chewing mixes food with saliva and forms a
bolus which can be easily swallowed
Mechanical digestion
Salivary amylase converts polysaccharides to
disaccharides
Chemical digestion
The ______ is a funnel shaped tube that extends
from the internal nares to the esophagus posteriorly
and to the larynx anteriorly
The pharynx is composed of skeletal muscle and
lined with mucous membrane
PHARYNX
The __________ is a collapsible, muscular tube that
lies posterior to the trachea and connects the
pharynx to the stomach
esophagus
The __________ is a J-shaped enlargement of the GI
tract
stomach
Mixes saliva, food, and gastric juice to form
chyme
Serves as a reservoir for food before release
into the small intestine
Secretes gastric juice, which contains HCl,
pepsin, intrinsic factor, and gastric lipase
Secretes gastrin into the blood
Functions of the Stomach
Lies posterior to the stomach
Produces enzymes that digest
carbohydrates, proteins, fats, and nucleic
acids
Produces sodium bicarbonate which buffers
stomach acid
Empties its contents into the duodenum
PANCREAS
The _______ makes bile, which is important in the
emulsification of fats
The gallbladder stores bile until it is needed
liver
The liver is composed of hepatocytes, bile
canaliculi, and hepatic sinusoids
Histology of the Liver
Carbohydrate, lipid, and protein metabolism
Processing of drugs and hormones
Bilirubin excretion
Bile salt synthesis
Storage
Phagocytosis
Vitamin D activation
Functions of the Liver and Gallbladder
The majority of digestion and absorption occur in the
SMALL INTESTINE (SI)
Segmentations mix chime with digestive juices and
bring food into contact with mucosa for absorption;
peristalsis propels chime through small intestine
Completes digestion of carbohydrates, proteins,
lipids; begins and completes digestion of nucleic
acids
Absorbs about 90% of nutrients and water that pass
through digestive system
Functions of the Small Intestine
Circular folds increase the surface area for
digestion and absorption in the small intestine
Circular Folds in the SI
___________ provides a vehicle for absorption of
substances from chyme as they come in contact
with the villi
Intestinal juice
_____________ enzymes, found on the surfaces of
the microvilli of absorptive cells, break down food
products
Brush border
Localized contractions
Segmentation
Propulsive contractions
Peristalsis
Digestion of:
Carbohydrates
Proteins
Lipids
Nucleic Acids
Chemical Digestion in the SI
Haustral churning, peristalsis, and mass peristalisis
drive contents of colon into rectum
Bacteria in colon convert proteins into amino acids,
break down amino acids, and produce some B
vitamins
Absorption of some water, ions, and vitamins
Formation of feces
Defecation
Functions of the Colon
Distension reaches a certain point and the walls
of the haustra contract to squeeze contents
onward
Haustral churning
A strong peristaltic wave that begins in the
transverse colon and quickly drives the contents
of the colon into the rectum
Mass peristalsis
The last stages of digestion occur through bacterial
action
Substances are further broken down by bacteria
Some vitamins are synthesized by bacterial
action
Chemical Digestion in the Colon
The colon absorbs water, electrolytes, and some
vitamins
Absorption
Consist of water, inorganic salts, sloughed-off
epithelial cells, bacteria, products of bacterial
decomposition, and undigested portions of food
Feces
Rectal wall distends and stretch receptors send
sensory nerve impulses to the sacral spinal cord
Motor impulses travel back to the descending
colon, sigmoid colon, rectum, and anus
Longitudinal rectal muscles contract and the
internal anal sphincter opens
Defecation Reflex
Stimulates gastric secretion and motility
Cephalic phase
Neural and hormonal mechanisms
Gastric phase
Neural and hormonal mechanisms
Intestinal phase
Decreased secretory mechanisms and
motility
Loss of strength and tone of digestive
muscular tissue
Changes in neurosecretory feedback
Diminished response to pain and internal
sensations
Aging and the Digestive System
Tooth decay
Periodontal diseases
Ulcers
Diverticula
Tumors
Hepatitis
Anorexia nervosa
Digestive System Disorders
