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Flashcards in Digestive System Deck (66)

function of the digestive system

mechanical digestion: breaks food down without altering chemical composition

chemical digestion: breaks food into simpler chemicals

ingestion, propulsion, absorption, defecation


the 4 layers of the wall of the alimentary canal

1. mucosa - formed of surface epithelium, underlying connective tissue, and a small amount of smooth muscle.

2. submucosa - contains considerable loose connective tissue as well as glands, blood vessels, lymphatic vessels, and nerves. nourish the surrounding tissues and carry away absorbed materials.

3. muscular layer provides movements of the tube, consists of two coats of smooth muscle tissue

4. serosa - outer layer covering the tube, functions in protecting underlying tissue and secreting serous fluid, which moistens and lubricates the tube's outer surface so the organs slide freely against one another


4 accessory organs to digestion

salivary glands - 3 major pair produce and empty saliva into mouth by ducts for the purpose of moistening and binding food together to make chewing and swallowing easier - also produce amylase to begin digestion of complex carbohydrates

pancreas - pancreatic juices contain enzymes that digest carbohydrates, fats, protein, and nucleic acids.

liver - oxidizes fatty acids at an especially high rate, metabolizes carbs, lipids, proteins, stores some substances, filters blood, destroys toxins, secretes bile.

gallbladder - stores bile between meals


3 pairs of salivary glands

parotid glands - anterior to and partially inferior to the ears, between the skin of the cheeks and the masseter muscles - secretion is clear, watery serous fluid, rich in salivary amylase

submandibular glands - in the floor of the mouth, on the inside surface of the mandible. secrets some serous fluid with some mucus, more viscous than parotid secretion

sublingual glands - floor of mouth, inferior to tongue (but above submandibular) - thick, stringy mucous.


4 types of teeth

incisor - sharp chisel shaped bite off large pieces of food - front 4 teeth on top & bottom

canine - cone shaped, grasp and tear food - two on top & bottom

premolar & molar - flat surfaces for grinding food particles


4 regions of stomach

cardia: small area near esophageal opening
fundus: balloons superior to the cardia - temporary storage area and sometimes fills with swallowed air

body: main part of stomach, between fundus and pylorus

pylorus: funnel-shaped portion that narrows and becomes the pyloric canal as it approaches the small intestine.


2 openings of the stomach & their valves

lower esophageal sphincter remain contracted and close the entrance to the stomach to prevent regurgitation of stomach contents into esophagus.

pyloric sphincter: valve that controls gastric empting


6 organs of the alimentary canal

mouth - mechanical breakdown of food, begins chemical digestion of complex carbs

pharynx - connects mouth with esophagus

esophagus - peristalsis pushes food to stomach

stomach - secrets acid & enzymes, mixes food with secretions to begin enzymatic digestion of proteins

small intestine - mixes food with bile and pancreatic juice, final enzymatic breakdown of food molecules, main site of nutrient absorption

large intestine - absorbes water & electrolytes to form feces

rectum - regulates elimination of feces


3 regions of the small intestine

receives secretions from pancreas and liver, completes digestion of the nutrients in chyme, absorbs products of digestion, transports residue to large intestine

duodenum - most fixed portion of the small intestine, follows a C shaped path

jejunum & ileum - no distinct separation between jejunum and ileum, but diameter of jejunum is usually greater, and its wall is thicker, more vascular, and more active than that of the ileum.

ileum has more lymph nodes and a higher baterial population


9 regions of the colon

absorbes water and electrolytes, makes poo, breaks down things not broken down in the small intestine (like cellulose)

ascending colon
transverse colon
descending colon
sigmoid colon
anal canal


4 lobes of the liver

major lobes:
larger right lobe
smaller left lobe

minor lobes
quadrate lobe - near gallbladder
caudate lobe - near inferior vena cava


ducts connecting the accessory organs to the small intestine

R & L hepatic ducts become the common hepatic duct, which joins w/ the cystic duct to become the bile duct


Steps in the swallowing mechanism

1. soft palate is elevated preventing food from entering nasal cavity

2. hyoid bone and larynx are elevated and the epiglottis closes to prevent food from entering the respiratory tract

3. tongue is pressed against the soft palate to force food into the posterior part of the oral cavity and keep it from re-entering the oral cavity

4. longitudinal muscles in the pharynx contract pulling the pharynx upward toward the food while inferior constrictor muscles relax to open esophagus

5. superior constrictor muscles contract and force food into esophagus


Difference between deciduous and permanent teeth

deciduous - erupt between 6 months and 4 years. no premolars, no third molar

permanent - come in around 6 years


buccal cavity

this is the mouth



hold food in mouth, muscles chew food



prevents food from entering the larynx



connects midline of tongue to the floor of the mouth





hard & soft palate

muscles draw soft palate and uvulva upward which closes the opening between the nasal cavity and the pharynx, preventing food from entering the nasal cavity


lingual tonsils

rounded masses of lymphatic tissue that cover the root of the tongue, posterior to and behind the tongue



judge temperature and texture of foods


palatine tonsils

help protect the body against infection (where tonsil stones are)



rough projections of the tongue which provide friction and helps handle food. also contains most of the taste buds


pharyngeal tonsils

behind soft palate, may be removed if enlarged


tongue body

mix food particles with saliva during chewing and move food toward the pharynx during swallowing


tongue root

covered with rounded masses of lymphatic tissue called lingual tonsils. connects tongue to hyoid bone



cone-shaped projection



narrow space between teeth, cheeks and lips


alveolar process

bone of the jaw inside gum which root of tooth is anchored to



superficial calcified substance covering the root of a tooth, attaches to periodontal ligament - connects to alveolar process via periodontal ligament



exposed region of tooth



hardest substance in the body, fairly brittle because it is heavily mineralized with calcium salts



bonelike material that underlies the enamel and forms the bulk of the tooth






area in gums where root and crown are connected


periodontal ligament

connects cementum to alveolar process, anchors tooth in jaw



contains connective tissue, blood vessels and nerve fibers, collectively called pulp which supplies nutrients to the tooth and provides for tooth sensations


pulp cavity

contains pulp



part of the tooth under the gingiva


root canal

extends into the root, blood vessels and nerves reach this cavity through the root canal


how contents of alimentary canal are mixed and moved

peristaltic waves push the chyme toward the pylorus of the stomach, and as chyme accumulates near the pyloric sphincter, this muscle begins to relax.

stomach contractions push chyme a little at a time into the small intestine.

as chyme filles the duodenum, internal pressure on the organ increases and stretches the intestinal wall.


discuss the effects of sympathetic and parasympathetic impulses on digestive actions

maintain muscle tone and regulate the strength, rate, and velocity of muscular contractions.

parasympathetic impulses increase actions of the digestive system

sympathetic nerve impulses oppose those of the parasympathetic division - inhibit certain digestive actions. inhibit mixing and propelling but stimulate contaction of sphincter muscles in the walls of the alimentary canal, blocking movement of materials through the tube


explain the process whereby the enzymes of the stomach and pancreas are activated

gastric secretions occur in 3 phases:

1. cephalic phase - before food reaches stomach, before you begin eating. parasympathetic reflexes operating through the vagus nervs stimulate gastric secretion at the taste, smell, sight, or thought of food. pancreas releases digestive enzymes

2. gastric phase: starts when food enters stomach. food triggers stomach to release gastrin, which stimulates production of more gastric juice.

as food enters the stomach and mixes with gastric juice, the pH of the content rises, which enhances gastric secretion. when pH reaches 3.0, secretion is inhibited. when it reaches 1.5, secretion ceases. pancreas releases digestive enzymes.

3. intestinal phase: begins when food leaves stomach and enters the small intestine. when food hits intestinal wall, it stimulates intestinal cells to releases intestinal gastrin, that enhances gastric gland secretion.

as more food enters the small intestine, a sympathetic reflex triggered by acid in the upper part of the small intestine inhibits secretion of gastric juice from the stomach wall.

secretin stimulates the pancreas to secrete fluid into the blood from the duodenal mucous membrane in response to the acid in chyme.


site of production + action: amylase

salivary glands

begins carb digestion by breaking down starch & glycogen to disaccharides


site of production + action: carboxypeptidase


breaks down peptides into amino acids


site of production + action: chymotrypsin and trypsin

breaks down proteins or partially digested proteins into peptides


site of production + action: enterokinase

intestinal enzyme

shortens trypsinogen to trypsin


site of production + action: lactase, maltase, sucrase

breaks down disaccharides into monosaccharides (sugars)


site of production + action: lipase

breaks down fat into fatty acids and glycerol


site of production + action: nuclease

breaks down nucleic acids into nucleotides


site of production + action: peptidase

breaks down peptides into amino acids


how do the secretions of liver + gallbladder enter the alimentary canal

state the actions of these secretions on food

bile is secreted by the liver and stored in the gall bladder. during digestion, bile is released from the gall bladder and enters the duodum to aid digestion of fats


how do the secretions of pancreas enter the alimentary canal

state the actions of these secretions on food

pancreatic duct secretes pancreatic juice into the small intestine, next to the bile duct.

pancreatic juice contains carb digesting enzymes, fat digesting enzymes, and protein splitting enzymes.


how do the secretions of salivary glands enter the alimentary canal

state the actions of these secretions on food

enter through stensen's (parotid), wharton's ducts (submandibular) and rivinus's ducts (sublingual)

breaks down carbs, also binds food and acts as a lubricant during swallowing


composition of gastric juice and action of each on food

pepsinogen - inactive form of pepsin (when this contacts HCl, it is activated)

pepsin - protein splitting enzyme that digests nearly all types of dietary protein

HCl - provides the acid environment needed for production and action of pepsin

mucus - provides a viscous, alkaline protective layer on stomach's inner surface

intrinsic factor - aids in vitamin b12 absorption


composition of intestinal juice and action of each on food

finish what the pancreas started

peptidase - after pancreatic juices breaka proteins down into peptides, peptidase breaks peptides into amino acids

sucrase, maltase, lactase: after pancreatic amylase breaks starch & glycogen into disaccharides, sucrase, maltase, and lactase break it down into monosaccharides

intestinal lipase: after pancreatic lipase breaks fat into fatty acids and glycerol, intestinal lipase breaks them further into more fatty acids and glycerol

enterokinase: shortens trypsinogen into tripsin



what stimulates production and indicate the target organ and action of the hormone

in response to food

target organ = stomach

increases secretory actvitity of gastric glands


intestinal gastrin

what stimulates production and indicate the target organ and action of the hormone

stimulated by chyme

target organ: intestine

increases secretory activity of gastric glands



what stimulates production and indicate the target organ and action of the hormone

stimulated by nervous system

secreted into stomach, pancreas & intestine

inhibits the secretion of acid by parietal cells


intestinal somatostatin

what stimulates production and indicate the target organ and action of the hormone

in response to fats

secreted into intestines

inhibits secretion of acid by parietal cells



what stimulates production and indicate the target organ and action of the hormone

in response to proteins and fats in the small intestine

secreted into intestines

decreases secretions of gastric glands and inhibits gastric motility, stimulates pancreas to secrete fluid with a high digestive enzyme concentration; stimulates gallbladder to contract and release bile



what stimulates production and indicate the target organ and action of the hormone

stimulated by acidic chyme entering small intestine

into the duodenum

stimulates pancreas to secrete fluid with a high bicarbonate ion concentration



regulates the rate at which chyme leaves the stomach. when the duodenum is filled with chyme, sensory stretch receptors are stimulated. sensory nerve impulses travel to central nervous system, and brain sends nerve impulse to inhibit peristalsis in stomach wall.


vomiting reflex

empties stomach in other direction. caused by irritation of stomach or intestines.

sensory impulses travel from site of stimulation to vomiting center in the medulla oblongata, and motor responses follow. stomach is squeezed from all sides and forces contents upward and out through the esophagus, pharynx, and mouth


defecation reflex

holding breath and contracting abdominal walls to increase internal abdominal pressure and force feces into rectum. as rectum fills, it triggers defecation reflex, which stimulates peristalsis in the descending colon. anal sphincter relaxes