42 notecards = 11 pages (4 cards per page)
2. Peristalsis( involves alternating waves of contraction and relaxationof muscles in the organ walls)
Digestive system organs fall into two main groups
1. The alimentary canal, or gastrointestinal (GI) tract (the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.)
2. Accessory digestive organs aid digestion physically and produce secretions that break down foodstuff in the GI tract; the organs involved are the teeth, tongue, gallbladder, salivary glands, liver, and pancreas.
of the abdominopelvic cavity its the most extensive of these membranes
covers the external surface of the most digestive organs
lines the body wall
is a double layer of peritoneum that extends to the digestive organs from the body wall. It allows blood vessels, lymphatics, and nerves to reach the digestive organs, and holds the organs in place as well as stores fat
1.is the simple act of putting food into the mouth
2. moves food through the alimentary canal and includes both swallowing and peristalsis
3. is the physical process of preparing the food for chemical
digestion and involves chewing, mixing, churning, and segmentation
organs not suspended by a mesentery. include most of the pancreas and parts of the small and large intestine
Define the splanchnic circulation
serves the digestive system and includes those arteries that branch off the abdominal aorta to serve the digestive organs and the hepatic portal circulation
Layers of the alimentary canal
1. Mucosa is the innermost, moist, epithelial membrane that lines the entire digestive tract. It secretes mucus, digestive enzymes, and hormones; absorbs digestive end products into the blood; and protects against infectious disease
2.the Submucosa is a moderately dense connective tissue layer
containing blood and lymphatic vessels, lymphoid follicles, and nerve
major function of the mucosa
- secrete mucus, digestive enzymes, and hormones
- absorb the end products of digestion into blood
- protect against infectious disease
the alimentary canal is constructed from either stratified squamous or simple columnar epithelium
Intrinsic nerve plexuses found in
the walls of the alimentary canal : the submucosal and meyenteric nerve plexuses
Basic function of mouth, lips and cheeks, tongue
-Mouth is a stratified squamous epithelial mucosa-lined cavity with boundaries of the lips, cheeks, palate, and tongue
-The lips and cheeks have a core of skeletal muscle covered externally by skin that helps to keep food between the teeth when we chew and plays a small role in speech.
-The tongue is made of interlacing bundles of skeletal muscle and is used to reposition food when chewing, mix food with saliva, initiate swallowing, and help form consonants for speech.
Function of saliva
- cleanes the mouth
-dissolves food chemical so they can be tasted
-moistens food and helps compact it into a bolus
- contains enzymes that begin the chemical breakdown of starchy foods
Most saliva produced by the
- the major or extrinsic salivary glands(outside oral cavity)
-minor or intrinsic salivary glands
The salivary glands are composed of two types of secretory cells
1. serous cell produce a watery secretion containing enzymes, ions, and tyni bit of mucin
2. mucous cell produce mucus, a stringly, viscous solution
Describe the mechanisms of chewing and swallowing.
•Mastication, or chewing, begins the mechanical breakdown of food and
mixes the food with saliva (p. 863).
(in stomach)a temporally "storage tank" where chemical breakdown of proteins begins and food is converted to a creamy paste
types of the gland cells
Mucous neck cells, found in the upper, or “neck,” regions of the glands, produce a thin, soluble mucus
Parietal cells,found mainly in the middle region of the glands, simultaneously secrete hydrochloric acid (HCl) and intrinsic factor. Although the parietal cells appear spherical when viewed with a light microscope, they actually have three prongs that bear dense microvilli (they look like fuzzy pitchforks!). This structure provides a huge surface area for secreting H and Cl into the stomach lumen. HCl makes the stomach contents extremely acidic (pH 1.5–3.5), a condition necessary for activation and optimal activity of pepsin. The acidity also helps in food digestion by denaturing proteins and breaking down cell walls of plant foods, and is harsh enough to kill many of the bacteria ingested with foods. Intrinsic factor is a glycoprotein required for vitamin B12 absorption in the small intestine.
Chief cells, occurs mainly in the basal regions of the gastric glands.he chief cells produce pepsinogen, the inactive form of the protein-digesting enzyme pepsin. Chief cells also secrete insignificant amounts of lipases (fat-digesting enzymes).
Enteroendocrine cells - (“gut endocrine”), typically located deep in the gastric glands, release a variety of chemical messengers directly into the interstitial fluid of the lamina propria.
is required for intestinal absorption of vitamin B12, needed to produce erythrocytes
Explain how gastric secretion and stomach motility are regulated.
Neural and hormonal mechanisms
Define and account for the alkaline tide.
As H is pumped from the cell and HCO3 (bicarbonate ion) accumulates within the cell,HCO3 is ejected through the basal cell membrane into the capillary blood. As a result, blood draining from the stomach is more alkaline than the blood serving it. This phenomenon is called the alkaline tide.
Identify and describe structural modifications of the wall of the small intestine that enhance the digestive process.
•the mucousa and submucousa are modified to reflect the intestines
functions in the digestive pathway
Differentiate between the roles of the various cell types of the intestinal mucosa.
simple columnar absorptive cells=nutrient and electrolyte absorption
is a fat emulsifier. Bile does not usually enter the small intestine until the gallbladder contracts when stimulated by cholecystokinin.
a waste product of the heme of hemoglobin formed during the breakdown of worn-out erythrocytes
stores and concentrates bile that is not needed immediately for digestion.
State the role of pancreatic juice in digestion.
•Pancreatic juice consists mainly of water and contains enzymes that
break down all categories of foodstuffs and electrolytes.
Describe how entry of pancreatic juice into the small intestine is regulated.
Pancreatic juice is regulated by neural stimuli and, more
importantly, hormones (cholecystokinin and secretin).
List the major functions of the large intestine.
The large intestine absorbs water from indigestible food residues and eliminates the latter as feces
Describe the regulation of defecation.
This spinal cord–mediated parasympathetic reflex causes the sigmoid colon and the rectum to contract, and the internal anal sphincter to relax. As feces are forced into the anal canal, messages reach the brain allowing us to decide whether the external (voluntary) anal sphincter should be opened or remain constricted to stop feces passage temporarily. If defecation is delayed reflex contractions end within a few seconds, and the rectal walls relax.With the next mass movement, the defecation reflex is initiated again—and so on, until the person chooses to defecate or the urge to defecate becomes unavoidable.
List the enzymes involved in chemical digestion; name the foodstuffs on which they act.
•salivary amylase - Chemical digestion of carbohydrates begins in the
mouth, where salivary amylase breaks large polysaccharides into
List the end products of protein, fat, carbohydrate, and nucleic acid digestion.
Describe the process of absorption of breakdown products of foodstuffs that occurs in the small intestine.
1.Large fat globules are emulsified (physically broken up into
smaller fat droplets) by bile salts in the duodenum.
is a catabolic process that breaks down large food molecules to monomers
Monosaccharides( simple sugar)
Describe embryonic development of the digestive system
1.The epithelial lining of the developing alimentary canal forms from
the endoderm with the rest of the wall arising from the mesoderm.
Describe abnormalities of the gastrointestinal tract at different stages of life
GI tract motility declines, digestive juice production decreases,
absorption is less efficient, and peristalsis slows, resulting in less
frequent bowel movements and often constipation.
are collections of fatty elements clustered together with bile salts in such a way that the polar (hydrophilic) ends of the molecules face the water and the nonpolar portions form the core
triglycerides are combined with lecithin and other phospholipids and cholesterol, and coated with a “skin” of proteins to form water-soluble lipoprotein droplets