A&P Flashcards
Two groups of organs make up the digestive system
(1) Gastrointestinal tract / Alimentary canal
(a) A continuous tube that extends from the mouth to the anus
(b) Mouth, pharynx, esophagus, stomach, small intestine, and large intestine
(2) Acessory digestive organs
(a) Organs that aid in digestion
(b) Teeth, tongue, salivary glands, liver, gallbladder, and pancreas
There are six basic functions of digestion
(1) Ingestion - taking in food and liquid through the mouth.
(2) Secretion - cells lining GI tract produces water, acid, buffers and enzymes to aid
digestion.
(3) Mixing and Propulsion – continuous contraction and relaxation moving food along the
GI tract.
(4) Digestion - mechanical and chemical process that breaks down the food we ingest.
(5) Absorption - small molecules produced in digestion moved into spaces to be used by
cells.
(6) Defecation - elimination of materials not absorbed by our body indigestion.
Throughout the GI tract from the esophagus to the anus, the linings of the walls are made up
of four distinct layers of tissues:
(1) Mucosa - innermost lining of the GI tract in direct contact with the substances passing
through.
(2) Submucosa - made up of areolar connective tissues that bind the mucosa to the
muscularis. Contains blood and lymphatic vessels which absorb food molecules as they
are broken down.
(3) Muscularis – contains skeletal (voluntary) muscles and smooth (involuntary) muscles.
(4) Serosa
) Serosa: Made up of two sub layers
(a) Visceral peritoneum – outermost layer around the organs of the GI tract.
(b) Parietal peritoneum) – lines the walls of the abdominal cavity.
(c) G (greater omentum) - “fatty apron” that drapes over the transverse colon and small
intestine
(d) M (mesentery) - binds the small intestine to the posterior abdominal wall
There are three pairs of salivary gland
Parotid – located inferior and anterior to the ears between the skin and the masseter
muscle.
(2) Submandibular – located medial and partly inferior to the mandible in the floor of the
mouth.
(3) Sublingual – beneath the tongue and superior to the submandibular glands.
saliva
(1) Helps dissolve foods and begins digestion.
(2) Made up of 99.5% water and 0.5% solutes.
(3) Contain lysozomes that kill bacteria protecting the mouth from infection and tooth decay.
function of the tongue.
a. The tongue is an accessory digestive organ, made up of skeletal muscle and forms the floor
of the oral cavity.
b. It is highly muscular, maneuvers food for chewing, and forces food to the back of the mouth
to be swallowed.
c. The frenulum is the fold of mucous membrane in the midline underneath the tongue that
limits the movement of the tongue posteriorly
function of the teeth.
a. The teeth are accessory organs of the GI tract, located in the bony sockets of the mandible
and maxilla.
b. They perform mechanical digestion by chewing and breaking down food into small pieces.
function of the pharynx.
A funnel shaped tube, located at the posterior end of the oral cavity, lined
with mucous membranes and is comprised of skeletal muscle.
The pharynx is divided into
three branches
(1) Nasopharynx: that is involved in respiration
(2) Oropharynx: located at the back of the mouth between the naso- and laryngopharynx
(3) Laryngopharynx: which helps to propel food into the esophagus via muscular
contractions
function of the esophagus
a. The esophagus is a muscular tube, lined with stratified squamous epithelium. It lies posterior
to the trachea.
b. The esophagus begins at the end of the pharynx and connects to the superior aspect of the
stomach. At each end, the muscularis forms two sphincters:
(1) Upper esophageal sphincter - composed of skeletal muscle
(2) Lower esophageal sphincter - composed of smooth muscle
c. The esophagus functions to transport food along its path while mixing it with mucous
Phases of swallowing
(1) Voluntary- Bolus forced into the oropharynx by the movement of the tongue upward and
backward against the palate.
(2) Pharyngeal- Begins when the bolus is in the oropharynx. Breathing is temporarily
interrupted. The soft palate and uvula move upward to close off the nasopharynx. The
epiglottis seals off the larynx. The upper esophageal sphincter relaxes and the bolus
moves into the esophagus.
(3) Esophageal- Begins when the bolus moves into the esophagus. Food is pushed through
the esophagus via peristalsis. When the bolus reaches the bottom of the esophagus the
lower esophageal sphincter relaxes and the bolus moves into the stomach.
function of the stomach
a. The stomach - J-shaped organ of the GI tract, serves as a reservoir and mixing chamber for
food. It aids in digestion.
(1) It extends from the end of the esophagus to the tip duodenum.
(2) Is the most elastic part of the GI tract.
(3) It can be stretched to accommodate up to 6.4 liters a of food.
(4) Has four main regions
(5) Gastric gland cells are exocrine cells that secrete 3 types of contents that combine to
create gastric juice
(6) Chyme
Has four main regions of the stomach
the cardia, fundus, body and pylorus
Gastric gland cells are exocrine cells that secrete 3 types of contents that combine to
create gastric juice
(a) Mucous neck cells – secrete mucous
(b) Chief cells – secrete pepsinogen
(c) Parietal cells
1) Secrete Hydrochloric acid (HCl) which helps convert pepsinogen into
pepsin (active digestive enzyme
a) Gastrin is the major hormonal regulator of HCL secretion
b) Gastrin is secreted by G cells in the pyloric antrum of the stomach
2) Secrete Intrinsic Factor (IF). IF is necessary for the absorption of
Vitamin B12 in the Small Intestines
a thick liquid with the consistency of pea soup in the stomach that is made up of
gastric juices and macerated food particles.
Chyme
function of the pancreas Endocrine functions
(a) There are specialized areas within the pancreas called islets of Langerhans.
(b) The islets of Langerhans are made up of different type of cells that make hormones
(c) The commonest ones are the beta cells, which produce insulin.
(d) Glucagon is a hormone that is produced by the alpha cells, found in the islets of
Langerhans.
(e) Glucagon’s role in the body is to prevent blood glucose levels dropping too low
one of the most important accessory organs within the Gastrointestinal
system
The pancreas
function of the pancreas exocrine functions
(1) It plays a vital role in chemical digestion
(2) It is a retroperitoneal organ that lies behind the stomach
(3) It passes secretions into the duodenum via the pancreatic duct
Pancreatic juice pH
7.1-8.2
a clear, colorless liquid made up of three enzymes that
consists mostly of water, some salts, and sodium bicarbonate
Pancreatic juice
protein digesting
starch (carbohydrate) digesting
triglyceride (fat) digesting
nucleic acid digesting
(1) Trypsin and chymotrypsin
(2) Pancreatic amylase
(3) Pancreatic lipase
(4) Ribonuclease
function of the liver and gallbladder
(1) Carbohydrate metabolism
(2) Lipid metabolism
(3) Protein metabolism
(4) Processing of drugs and hormones
(5) Excretion of bilirubin
(6) Storage of vitamins and minerals
(7) Activation of vitamin D
second largest organ in the body located just below the diaphragm, mostly on the
right side of the body
liver
Major functional cells of the liver that perform metabolic, secretory and
endocrine functions
Hepatocytes
A pear-shaped sac that hangs from the inferior margin of the liver.
gallbladder
function of the gallbladder
(1) Stores bile to be released into the small intestine.
(2) Aids in chemical digestion, especially digestion of fats
function of the small intestine.
(3) Most of the digestion and absorption events occur here.
(a) Digestion
1) Mechanical via segmentation and peristalsis
2) Chemical via pancreatic enzymes, bile and intestinal juice
(b) Absorption
1) Carbohydrates: Broken down by enzymes and absorbed as
monosaccharides
2) Proteins: Broken down by enzymes into amino acids, dipeptides and
tripeptides
3) Triglycerides (fats): Broken down by enzymes and absorbed as
monoglycerides and fatty acids
4) Absorption of ions and water.
5) Absorption of vitamins A, D, E and K.
The small intestine is divided into three different segments
(a) Duodenum - Attaches to the pyloric sphincter of the stomach.
(b) Jejunum - Middle section of small intestine.
(c) Ileum - Attaches to the large intestine at the ileocecal sphincter/valve
length of the small intestine
Approx 3m (10ft) long in a living person but, stretches out to 6.5m (21ft) in a cadaver.
the segment in the GI system that comes after the stomach
small intestine
e function of the large intestine
(1) Complete absorption – absorbs water, electrolytes and vitamins.
(2) Absorbs certain vitamins produced by healthy gut bacteria – vitamins B and
K. These are needed for normal metabolism.
(3) Forms feces (unabsorbed digested material) to be expelled from the body
The last part of the GI tract
large intestine
The large intestine has four regions
(1) Cecum – First segment of the large intestine. The appendix attaches here.
(2) Colon – Broken down into ascending, transverse, descending and sigmoid portions.
(3) Rectum – Connects the sigmoid colon to the anus.
(4) Anal canal – last 2-3 cm of the rectum consisting of internal (involuntary) and external
(voluntary) sphincters
There are three phases of digestion
(1) Cephalic – The smell, sight, sound or thought of food activates neural centers in the brain
stimulating the salivary glands to secrete saliva and the gastric glands tosecrete gastric
juice.
(2) Gastric – Starts when food enters the stomach. Gastrin is released promoting the release
of gastric juice which increases the mobility of the stomach, relaxes the pyloric sphincter
and promotes gastric emptying.
(3) Intestinal – Starts when food enters the small intestine. Inhibitory effects slow gastric
emptying and excitatory effects stimulate the secretion of pancreatic juices to aid in
absorption and digestion.
