Digestive System Flashcards
Name the parts of the alimentary canal and their overall function
a. Mouth, pharynx, esophagus, stomach, small intestine, and large intestine
b. Digests and absorbs food
Name the accessory digestive organs
a. Teeth, tongue, gallbladder
b. Digestive glands
i. Salivary glands
ii. Liver
iii. Pancreas
Describe the layers of the peritoneum and peritoneal cavity
a. Peritoneum: serous membrane of the abdominal cavity
i. Visceral peritoneum on external surface of most digestive organs
ii. Parietal peritoneum lines the body wall
b. Peritoneal cavity between the two layers
i. Fluid lubricates mobile organs
c. Mesentery is a double layer of peritoneum
i. Routes for blood vessels, lymphatics, and nerves
ii. Holds organs in place and stores fat
d. Peritoneal organs are surrounded by the peritoneum
e. Retroperitoneal organs lie posterior to the peritoneum
Describe the blood supply of the digestive system
a. Arteries
i. Hepatic, splenic, and left gastric
ii. Inferior and superior mesenteric
b. Hepatic portal (system) circulation
i. Drains nutrient-rich blood from digestive organs
ii. Delivers it to the liver for processing
Describe the four basic layers (tunics) of the alimentary canal and cell type
a. Mucosa
b. Submucosa
c. Muscularis externa
d. Serosa
Describe mucosa tunica (function and location)
a. Lines the lumen
b. Simple columnar epithelium
c. Functions
d. Secretes mucus, digestive enzymes and hormones
e. Absorbs products of digestion
f. Protects against infectious disease
Describe submucosa tunica (tissue, etc)
a. Dense connective tissue
b. Blood and lymphatic vessels and lymphoid follicles
c. Has landmarks that give hints of where you are in the alimentary canal
Describe the muscularis externa tunica
a. Smooth muscle
b. Responsible for segmentation and peristalsis
c. Inner circular and outer longitudinal layers
d. Sphincters in some regions
Describe the parts of the mouth (oral cavity )
a. Oral (buccal) cavity
b. Bounded by lips, cheeks, palate, and tongue
c. Lined with stratified squamous epithelium
Describe the ANS activity in the enteric nervous system
a. Long ANS fibers synapse with enteric plexuses
b. Sympathetic impulses inhibit secretion and motility
c. Parasympathetic impulses stimulate
What is the median attachment of each lip to the gum?
Labial frenulum
Describe the palate (hard and soft)
a. Hard palate: maxilla and palatine bones
b. Soft palate: fold of skeletal muscle
c. Uvula projects downward from its free edge
Describe the tongue (function, muscles, attachment)
a. Functions include
i. Formation of the food bolus
ii. Initiation of swallowing, speech, and taste
b. Intrinsic and extrinsic muscles change the shape and position of the tongue
c. Lingual frenulum: attachment to the floor of the mouth
Describe the tongue papillae
a. Surface bears papillae
b. Filiform—whitish, give the tongue roughness and provide friction
c. Fungiform—reddish, scattered over the tongue
d. Circumvallate (vallate) papilla—V-shaped row in back of tongue
i. These three house taste buds
e. Foliate—on the lateral aspects of the posterior tongue (for texture)
Which three papillae have taste buds?
a. Filiform
b. Fungiform
c. Circumvallate
Describe salivary glands
a. Secretion (saliva)
b. Cleanses the mouth
c. Moistens and dissolves food
d. Aids in bolus formation
e. Contains enzymes (amylases) that begin the breakdown of starch
i. Polysaccharides turned into smaller polysaccharides + disaccharides
ii. Breaks glycosidic bonds between the monosaccharides
Describe composition of saliva
a. 98% water, slightly acidic solution containing:
b. Salivary amylase and lingual lipase
i. Breaks triglycerides into glycerol + fatty acids
ii. Breaks ester bonds
c. Mucin traps inhaled particles
d. Lysozyme, defensins, and IgA antibodies protect against microorganisms
Describe salivary glands
a. 3 pairs of salivary glands
b. Parotid – near the ear; Stenson’s duct leads to the mouth – inflammation leads to mumps
c. Submandibular – floor of the inner jaw; Wharton’s ducts open under the tongue lateral to the frenulum
d. Sublingual – smallest glands; under tongue
Describe pharynx
a. Oropharynx and laryngopharynx
b. Allow passage of food, fluids, and air
c. Peristalsis begins in the pharynx
Describe esophagus
a. Flat muscular tube from laryngopharynx to stomach
b. Pierces diaphragm at esophageal hiatus
c. Joins stomach at the cardiac sphincter (LES)
d. No digestive enzymes secreted here
Describe digestive processes of the mouth
a. Physical digestion (primarily mastication)
b. Chemical digestion (salivary amylase and lingual lipase)
c. Deglutition (swallowing)
Describe the anatomy of the stomach
a. Cardiac region - Surrounds the cardiac sphincter
b. Fundus - Dome-shaped region beneath the diaphragm
c. Body – Larger midportion
d. Pyloric region - Continuous with the duodenum through the pyloric sphincter
Describe microscopic anatomy of mucosa of the stomach
a. Simple columnar epithelium
b. Gastric pits lead into gastric glands
Describe processes in the stomach
a. Physical, muscular, mechanical digestion
b. HCl and other acids denature proteins
c. Secretion of intrinsic factor required for absorption of vitamin B12 in your stomach
d. Digestion of proteins by pepsin
e. Gastrin is released thru positive feedback and stimulates release of all other gastric secretions
f. Delivery of chyme to the small intestine
Name two homeostatic imbalances of the stomach
a. Gastritis: inflammation caused by anything that breaches the mucosal barrier
b. Peptic or gastric ulcers: erosion of the stomach wall - most are caused by Helicobacter pylori (live in acid)
Describe nausea
a. Diminished stomach movements from stimulation of vomiting center in medulla oblongata
b. Vomiting Center empties stomach in reverse direction – may purge as far down as cecum! (contains feces)
- Describe gastric contractile activity
a. Basic electrical rhythm (BER) initiated by pacemaker cells (cells of Cajal)
b. Peristaltic waves move toward the pylorus at the rate of 3 per minute
c. Most vigorous contractions near the pylorus
d. Chyme is either:
i. Delivered in 3-ml spurts to the duodenum, or
ii. Forced backward into the stomach
Describe regulation of gastric emptying
a. As chyme enters the duodenum receptors respond to stretch and chemical signals
b. Carbohydrate-rich chyme moves quickly through the duodenum
c. Fatty chyme remains in the duodenum 6 hours or more
Describe small intestine and its subdivisions
a. Major organ of digestion AND absorption
b. From pyloric sphincter to ileocecal valve
c. Subdivisions
i. Duodenum (retroperitoneal) ~25 cm
ii. Jejunum ~2.3 m
iii. Ileum ~3.5 m
Name the ducts/accessories that enter the duodenum and pancreas from the gallbladder
a. Right and left hepatic duct
b. Common hepatic duct
c. Cystic duct
d. Common bile duct
e. Pancreatic duct
f. Hepatopancreatic ampulla and sphincter
Describe intestinal folding (structure and function)
a. Increase surface area for nutrient absorption
b. Circular folds (don’t care)
c. Villi
d. Microvilli (aka brushborder)
What are villi?
a. Motile fingerlike extensions of the mucosa
b. Simple columnar cells with goblet cells (secrete mucus)
c. Contain lacteal
What are microvilli?
Projections (brush-border) of absorptive cells that bear enzymes (enteropeptidases)
Describe intestinal crypts (of Lieberkuhn)
a. Intestinal crypt epithelium
i. Secretory cells that produce intestinal juice
Describe the submucosal glands
a. Duodenal (Brunner’s) glands of the duodenum secrete alkaline mucus (raspberry shaped)
b. Peyer’s patches of ileum protect distal intestine from against bacteria (triangle or bear paw shaped)
Describe liver
a. Largest gland in the body
b. Over 200 known functions
c. Highly regenerative, multinucleate cells
d. Four lobes—right, left, caudate, and quadrate
Describe the falciform ligament of the liver
a. Separates the right and left lobes
b. Suspends liver from the diaphragm
c. Round ligament (ligamentum teres) is Remnant of fetal umbilical vein
Describe the associated structures of the liver
a. Lesser omentum anchors liver to stomach
b. Common hepatic duct leaves the liver
Describe the liver lobules
a. Hexagonal structural and functional units
i. Filter and process nutrient-rich blood
ii. Composed of plates of hepatocytes
iii. Longitudinal central vein
b. Portal triad at corners of lobules
i. Bile duct receives bile
ii. Portal arteriole is a branch of the hepatic artery
iii. Portal venule is a branch of the hepatic portal vein
c. Liver sinusoids are leaky capillaries between hepatic plates
d. Kupffer cells (hepatic macrophages) in liver sinusoids
List the hepatocyte functions
a. Blood filtering / reservoir
b. Store fat-soluble vitamins (A, D, B12)
c. Perform detoxification
d. Produce nearly 1L bile per day
Describe metabolism of carbohydrates
a. Glycogenesis: glucose to glycogen
b. Glycogenolysis: glycogen to glucose
c. Gluconeogenesis: synthesize glucose from a non-sugar
Describe metabolism of lipids
a. Oxidation of fatty acids (not important)
b. Synthesize phospholipids and cholesterol
c. Transport fats to adipose tissue for storage (not important)
Describe metabolism of proteins
a. Deamination of amino acids
b. Form urea
c. Synthesize plasma proteins (like fibrinogen and clotting factors)
Describe bile
a. Bitter greenish-brown alkaline fluid that aids digestion and is secreted by the liver and stored in the gallbladder
b. Bile salts: cholesterol derivatives that function in fat emulsification
- Describe the gallbladder
a. Muscular sac on the ventral surface of the liver
b. Stores and concentrates bile
c. Releases bile via the cystic duct
d. Gallstones = solid, crystalline cholesterol (not rock)
Where is the pancreas located?
a. Mostly retroperitoneal, deep to the greater curvature of the stomach
b. Head is encircled by the duodenum; tail abuts the spleen
Describe endocrine and exocrine function of liver
a. Endocrine function
i. Pancreatic islets secrete insulin and glucagon
b. Exocrine function
i. Acini secrete pancreatic juice for a variety of purposes
ii. Granules of secretory cells contain digestive enzymes
Describe pancreatic juices
a. Bicarbonate-rich, alkaline solution that neutralizes acidic chyme
b. Enzymes:
c. Amylase and lipases are secreted in active form
d. Proteases are secreted in inactive form to complete protein digestion
e. Maltase, sucrose, lactase, and other brush-border enzymes complete carb digestion
Describe digestion of the small intestine (no direct questions on test)
a. Slow movement allows for digestion and absorption throughout the length of the small intestine
b. Chyme from stomach contains unharvested nutrients:
c. Partially digested carbohydrates and proteins
d. Undigested fats and nucleic acids
- Describe protease activation in duodenum (pancreatic juice)
a. Trypsinogen is activated to trypsin by brush border enzyme enteropeptidase
b. Subsequently, procarboxypeptidase and chymotrypsinogen are both activated by trypsin
Describe cholecystokinin (CCK)
a. Secreted from duodenal enteroendocrine cells that are exposed to chyme
b. CCK causes gallbladder contraction
c. CCK causes the hepatopancreatic sphincter to relax
Describe motility of the small intestines
a. Peristalsis:
b. Initiated in the late intestinal phase
c. Each wave starts distal to the previous
d. Meal remnants, bacteria, and debris are moved to the large intestine
Describe large intestine
a. Unique features
i. Teniae coli (like a rubber band shorter than length of colon, causing it to bunch up into haustra)
1. Three bands of longitudinal smooth muscle in the muscularis
b. Haustra
i. Pocketlike sacs caused by the tone of the teniae coli
c. Epiploic appendages (not important)
i. Fat-filled pouches of visceral peritoneum
Describe regions of the large intestine
a. Regions
b. Cecum (pouch with attached vermiform appendix)
c. Colon
d. Rectum
e. Anal canal
What are the functions of the large intestine?
a. Remember, no digestion is occurring here
b. Vitamins (K), water, and electrolytes are reclaimed
c. Major function is propulsion of feces and defecation
d. Colon is not essential for life
Describe motility of the large intestine
a. Gastrocolic reflex
i. Initiated by presence of food in the stomach
ii. Activates three to four slow powerful peristaltic waves per day in the colon (mass movements to rectum)
Describe defecation
a. Mass movements force feces into rectum
b. Distension initiates spinal defecation reflex
c. Parasympathetic signals stimulate contraction of the sigmoid colon and rectum
d. Conscious control allows relaxation of external anal sphincter
Overview of chemical digestion and absorption of carbohydrates
a. Digestive enzymes
i. Salivary amylase
ii. Pancreatic amylase
iii. Brush border enzymes dextrinase, glucoamylase, lactase, maltase, and sucrase
Overview of chemical digestion and absorption of proteins
a. Enzymes
i. Pepsin in stomach
ii. Pancreatic proteases
1. Trypsin
2. Chymotrypsin
3. Carboxypeptidase
b. Other brush border enzymes
Overview of digestion and absorption of lipids
a. Pre-treatment- emulsication by bile salts
b. Enzymes- pancreatic lipase
Overview of vitamin absorption
a. In large intestine
b. Vitamin K and B- vitamins from bacterial metabolism are absorbed
