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The Digestive System
Anatomy and Physiology of the Digestive System
123
Anatomy
12th Grade
05/18/2011

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Term
What is the function of the digestive system?
Definition
takes in food, breaks it down to the nutrient molecular level, absorbs them into the bloodstream, rids the body of indigestible remains
Term
What 2 categories do digestive system organs fall under?
Definition
1. Alimentary canal
2. Accessory organs
Term
Alimentary Canal (aka Gastrointestinal Tract or gut)
Definition
Continuous tube that winds through the body where food is digested and absorbed
Term
Accessory digestive organs
Definition
Secrete enzymes to help with digestion or contribute to breakdown of food (teeth, tongue, salivary glands, gallbladder, liver, pancreas)
Term
6  Steps of Digestive Process
Definition
1. Ingestion
2. Propulsion
3. Mechanical Digestion
4. Chemical Digestion
5. Absorption
6. Defecation
Term
Ingestion
Definition
Entrance of food into the GI tract, usually by mouth
Term
Propulsion
Definition
Includes swallowing and peristalsis - wave of smooth muscle contraction to push food along GI tract
Term
Mechanical Digestion
Definition
Physically preparing food for chemical digestion (chewing, mixing of food, churning in stomach)
Term
Chemical Digestion
Definition
Breaks food down to the building block molecules (fats to fatty acids, starches to glucose, proteins to amino acids)
Term
Absorption
Definition
Passage of digested molecules, vitamins, minerals, and water into blood and lymph; on the average, up to 10L of food, water, and GI secretions enter the alimentary tract daily
Term
Defecation
Definition
Elimination of indigestible substances through anus in the form of feces
Term
2 Mechanisms that control the digestive system
Definition
1. Variety of mechanical and chemical stimuli in walls of tract (stimulate or inhibit digestion)
2. Nerves along tract and endocrine glands (controls both intrinsic and extrinsic)
Term
The Mouth/Oral Cavity/Buccal Cavity
Definition
lined with mucus and stratified squamous epithelium (for lots of friction), boundaries are the lips, cheeks, tongue, and palate.
Term
Oral oriface
Definition
Anterior opening of mouth
Term
Oropharynx
Definition
Posterior opening to mouth
Term
Lips and Cheeks
Definition
skeletal muscle surrounded by skin, keep food between teeth for chewing, used in speech
Term
Red Margin
Definition
red area of lips, where keratinized skin meets the mucous layers, translucent – see red from blood vessels
Term
Palate
Definition
roof of mouth – both hard palate (anterior, bony) and soft palate (muscle, posterior).
Term
Hard Palate
Definition
for tongue to push food against when chewing\
Term
Hard Palate
Definition
for tongue to push food against when chewing
Term
Soft Palate
Definition
includes uvula, closes off nasopharynx when we swallow
Term
Tongue
Definition
occupies the space of the oral cavity, “tied” to the floor of mouth, made of skeletal muscle, constantly repositions food between teeth while chewing
Term
Bolus
Definition
ball/mass of food and saliva pushed into pharynx by tongue
Term
Salivary glands
Definition
parotid, sublingual, submandibular – produce saliva
Term
Functions of saliva
Definition
1. Cleanses mouth
2. Dissolves food so it can be tasted by taste buds
3. Moistens, lubricates food and helps form the bolus
4. Contains enzymes that begin the breakdown of starches into sugars
5. Contains chemicals/antibodies to protect against microorganisms
Term
Teeth
Definition
lie in sockets of the gum covered jaw bones, used to masticate or chew food; First teeth to grow – baby or deciduous; Permanent – grow in until the age of 25, 32 of them; classifies by shape – incisors, canines, premolars, molars; Several layers – enamel, dentine, pulp in center
Term
Deglutition
Definition
complicated process involving 22 muscles, occurs in 2 phases: Buccal phase and Pharyngeal-esophageal phase
Term
Buccal phase (deglutition)
Definition
occurs in mouth and is voluntary, tongue pushes on hard palate, tongue contracts and pushes bolus into oropharynx, then becomes involuntary reflex
Term
Pharyngeal-esophageal Phase
Definition
controlled by the swallowing center in the brain (the pons and medulla;  Breathing inhibited, tongue blocks off mouth, soft palate blocks off nasopharynx, epiglottis covers trachea, esophageal muscles and sphincters relax to open esophagus
Term
Esophagus
Definition
muscular tube about 10 inches long, flattened, and collapsed when not involved in food propulsion; runs behind heart, through mediastinum, through the diaphragm; Joins the stomach at the cardiac orifice;  Has 4 layers: stratified epithelial layers, mucus, smooth muscle, skeletal muscle, fibrous layers
Term
Heartburn
Definition
gastroesophageal reflux disease (GERD; Burning pain when acids and enzymes from stomach are released up into esophagus (overeating, exercise, stress)
Term
Hiatal hernia
Definition
weakening of the cardiac sphincter (muscle) around the cardiac orifice – allows stomach to come up through diaphragm, allows fluids from stomach to enter esophagus, especially when lying down
Term
Stomach
Definition
 Where GI Tract expands, forms a temporary “storage tank” where chemical breakdown of proteins begins and where food is converted to a creamy paste called chyme;  Varies in size from 6-10 inches long but diameter and volume depends on how much food is consumed
Term
Rugae
Definition
large, longitudinal folds in stomach (what you hear when stomach growls)
Term
6 Layers of Stomach
Definition
Cardiac region, fundus, body, pyloric region, greater curvature, lesser curvature
Term
Cardiac region of stomach
Definition
aka cardia – area surrounding the cardiac orifice where food enters from the esophagus
Term
Fundus (stomach)
Definition
dome shaped part beneath the diaphragm, bulges upward
Term
Body (Stomach)
Definition
midportion or length
Term
Pyloric region (stomach)
Definition
has 3 parts – pyloric antrum, pyloric canal, and the pylorus – continuous with the duodenum of the small intestine, has pyloric sphincter that keeps stomach closed
Term
Greature curvature (stomach)
Definition
convex, inferior, lateral surface
Term
Lesser curvature (stomach)
Definition
concave, superior, medial surface
Term
2 membranes that tie the stomach to other organs and to the body wall attached to the curvatures
Definition
Lesser omentum and greater omentum
Term
Lesser omentum
Definition
from liver to lesser curvature
Term
Greater omentum
Definition
from stomach, drapes over the small intestine – filled with lymph cells and fat cells, and drapes over the body like an apron.
Term
3 layers of smooth muscle (stomach)
Definition
longitudinal, circular, and oblique – allows stomach to churn and mix food as well as peristaltic movements
Term
Interior glands and secretions (Stomach)
Definition
Mucous cells, Parietal cells, Chief cells, Enteroendocrine cells
Term
Mucous cells
Definition
produces 2 layer thick barrier of mucous to protect stomach wall
Term
Parietal cells
Definition
make and secrete HCl and intrinsic factor
Term
HCl
Definition
to kill germs, helps break down proteins, allows enzymes to function
Term
Intrinsic Factor
Definition
needed to absorb vitamin B
Term
Chief cells
Definition
make pepsinogen, which forms pepsin – enzyme to digest proteins
Term
Enteroendocrine cells
Definition
release a variety of chemicals and hormones (histamins, serotonin, gastrin, etc.) that help stimulate digestive system, regulate stomach action
Term
3 subdivisions of small intestine
Definition
the duodenum, the jejunum, and the ileum
Term
Duodenum
Definition
shortest section, but the most features, curves around pancreas, where the pancreatic and bile duct (from liver) both empty
Term
Jejunum
Definition
between the duodenum and the ileum, coils in the center part of abdominal cavity.
Term
Ileum
Definition
last part of the small intestine, joins the large intestine
Term
3 structural features to increase surface area in small intestine
Definition
Plicae circulares, Villi, microvilli
Term
Plicae circulares
Definition
deep folds in mucus lining
Term
Villi
Definition
projections that give the interior of the small intestine a velvety texture, contain smooth muscle to help pulsate and mix contents into texture for better absorption
Term
Lacteals
Definition
In villi; lymph vessels to absorb nutrients as well as blood vessels.
Term
Intestinal juice
Definition
mostly water, antimicrobial chemicals, mucous, and bicarbonate chemicals to neutralize acid from stomach (secreted from intestinal glands between villi)
Term
Microvilli
Definition
tiny projections on surface of each cell in the villi to increase surface area even more
Term
3 functions of large intestine
Definition
to absorb water from wastes, temporarily holds wastes in rectum, eliminate solid wastes from body (feces)
Term
3 features not seen in other organs (large intestine)
Definition
Teniae coli, Haustra, Epiploic appendages
Term
Teniae Coli
Definition
3 bands of smooth muscle that run longitudinally, no circular muscles.
Term
Haustra
Definition
pocket-like sacs along the length (caused by teniae coli)
Term
Epiploic appendages
Definition
fat-filled pouches that hang from the surface (function undetermined)
Term
5 subdivisions of the large intestine
Definition
Cecum, Appendix, Colon, Rectum, Anal canal
Term
Cecum
Definition
sac-like pouch at the beginning of the large intestine (at the ileocecal valve)
Term
Appendix
Definition
(aka vermiform appendix) wormlike small tubular pouch, contains masses of lymphoid tissue, used from immunity, but often gets infected with bacteria that get get trapped in its twisted shape
Term
Colon
Definition
bulk of large intestine – has 4 distinct areas – ascending, transverse, descending, sigmoid.
Term
Rectum
Definition
lies in front of sacral vertebrae where feces are temporarily stored.
Term
Anal canal
Definition
lies outside pelvic cavity, opens to body exterior, controlled by muscles (both smooth and skeletal)
Term
Bacterial flora
Definition
Inside large intestine; most are harmless or even beneficial – aid in the digestion of cellulose, manufacture vitamin B and K, but produce gas
Term
Diarrhea
Definition
when food is rushed through the large intestine – water isn’t absorbed
Term
Constipation
Definition
when food remains in colon too long, too much water is absorbed, feces is difficult to eliminate
Term
Bile
Definition
fat emulsifier – breaks fat down into little pieces, increase surface area for enzymes to work better
Term
Liver
Definition
largest gland in body, about 3 lbs; Upper right quadrant, under ribs and diaphragm; produces bile
Term
Falciform ligament
Definition
divides liver into right and left, suspends liver from diaphragm
Term
Round ligament
Definition
remains of fetal umbilical vein
Term
Liver lobules
Definition
(hexagonal shaped structures made of groups or plates of liver cells; Plates radiate out from a central vein that runs along the central axis
Term
hepatocytes
Definition
liver cells
Term
Portal triads
Definition
At each of the 6 corners of liver lobule; consist of vein, artery, and a bile duct
Term
Liver function
Definition
1. Produce bile
2. Produce nutrients (excess glucose to glycogen, amino acids to plasma proteins, etc.)
3. Store fat soluble vitamins
4. Detoxification – ammonia to urea, drugs, etc.
Term
Bile
Definition
Basic; Contains pigments (RBC), bile salts, cholesterol, triglycerides, phospholipids, electrolytes; stored in gallbladder, where it’s concentrated; released through cystic duct, then into duodenum through bile duct
Term
Pancreas
Definition
Soft, tapered gland that extends across the abdomen, under the stomach, and surrounded by the duodenum;  Drains juices through main pancreatic duct and fuses with the bile duct from the gall bladder and dumps into the duodenum
Term
Pancreatic juices
Definition
a mixture of enzymes to digest all categories of food (Fats, proteins, carbohydrates)
Term
Acini
Definition
Clusters of cells that produce the pancreatic juices
Term
Pancreatic islets
Definition
produce insulin and glucagon – hormones important in carbohydrate metabolism
Term
Epithelial cells in lining of pancreas
Definition
make bicarbonate ions to neutralize acid
Term
Chemicals from pancreas
Definition
released in the inactive form; don’t become active until they mix with basic environment of the duodenum. (example – trypsinogen becomes trypsin to digest protein)
Term
3 Pancreatic enzymes
Definition
1. Amylase – digests carbohydrates
2. Lipase – digests fats
3. Nucleases – digest nucleic acids (DNA & RNA
Term
Chemical digestion
Definition
process in which large food molecules are broken down into monomers
Term
Monomers
Definition
small chemical building blocks that are absorbed by the GI tract
Term
Hydrolysis
Definition
involves adding a water molecule to break bonds
Term
Monosaccharides
Definition
simple sugars that do not need digested, absorbed directly – glucose, fructose, and galactose
Term
Disaccharides
Definition
“double” sugars – only 2 molecules together that need split or digested – includes sucrose, lactose, and maltose
Term
Polysaccharides
Definition
many sugars – includes complex sugars such as starches, glycogen, and cellulose (cellulose is indigestible, “fiber” good at cleaning GI tract)
Term
Salivary amylase
Definition
Sugar/starch digestion; begins in the mouth
Term
maltase, sucrose, lactase
Definition
in small intestine; other enzymes for specific sugars
Term
Amino acids
Definition
monomers of protein
Term
trypsin, chymotrypsin, carboxypeptidase, aminopeptidase and dipeptidase
Definition
secreted by pancreatic cells; in the small intestine; digests proteins not digested in the stomach
Term
Saturated lipids
Definition
molecules are covered with hydrogen atoms, tend to be solids at room temperature
Term
Unsaturated lipids
Definition
less hydrogen due to double bonds between atoms, usually liquid at room temperature (healthier for humans)
Term
Polyunsaturated lipids
Definition
healthiest type of fat
Term
Fats/oils digestion
Definition
Non-water soluble so must be “pretreated” with bile salts to be emulsified -reduces the attraction between the fat molecules so they become further apart, big drops broken down to many little drops; digested only by the pancreatic lipase
Term
fatty acids, monoglycerides, and glycerol
Definition
monomers of fats
Term
Nucleic acids
Definition
the DNA and RNA contained in the nuclei of the cells of the food we eat
Term
pancreatic nuclease
Definition
digests the DNA and RNA to the nucleotide monomers in the small intestine
Term
nucleotidases and phosphatases
Definition
small intestine;breaks down nucleotides to their building blocks
Term
Remains of small intestine that move on to large intestine
Definition
some water, indigestible cellulose and fiber, and millions of bacteria
Term
Mumps
Definition
viral infection of the parotid salivary glands, spread through saliva, Can cause high fevers in adult males, a 25% risk of sterility.
Term
Gastric ulcers
Definition
erosion of stomach wall, where the mucus barrier of the stomach has been compromised, very painful, can lead to perforated bacterial infections.
Term
Vomiting
Definition
aka emesis – reverse peristalsis where food stuff is forced up esophagus; most often caused by overeating or irritants (bacteria, toxins, etc.)
Term
Hepatitis
Definition
inflammation of the liver, most often due to viral infections, also poisonings, rates of hepatitis have dropped in US due to vaccinations, sanitation, and medication.
Term
Cirrhosis
Definition
chronic inflammation of the liver, usually brought on by alcoholism, liver becomes scarred & fatty, stops functioning.
Term
Gallstones
Definition
when bile salts & cholesterol from liver crystallize and form stones, can block bile duct, usually requires surgery.
Term
Appendicitis
Definition
acute inflammation of the appendix that results from blockage (usually feces) of the opening/lumen, eventually the appendix swells, can rupture or cause tissue death.
Term
Peritonitis
Definition
infection of the peritoneum – serous membrane that covers the abdomen, usually from wounds or ruptured appendix
Term
Inflammatory Bowel Disease
Definition
non-contagious periodic inflammation of the bowel, most often caused by an abnormal immune response to bacteria in intestine, painful, includes diarrhea, bleeding from ulcers, weightloss; 2 types: crohn's disease and colitis
Term
Crohn's disease
Definition
deep ulcers and inflammation along length of small intestine but mostly ileum.
Term
Crohn's disease
Definition
deep ulcers and inflammation along length of small intestine but mostly ileum.
Term
Colitis
Definition
in large intestine, mainly in rectum – both treated with drugs, diet.
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