23 1-8 Flashcards
Function of the digestive system?
Takes in food, breaks it down into nutrient molecules, absorbs these molecules, rids the body of indigestible remains.
Organs of the alimentary canal/digestive tract?
Mouth, pharynx, esophagus, stomach, small intestine, large intestine
Accessory structures?
Teeth, tongue, gallbladder, salivary glands, liver, pancreas
What are the major processes occurring in the digestive system?
Ingestion, propulsion, mechanical breakdown, digestion, absorption, defacation
Ingestion
Taking food into the digestive tract
Propulsion/motility
Moving of food through the alimentary canal - peristalsis, swallowing
Mechanical breakdown/digestion
Physical process of preparing food for chemical digestion - chewing, mixing, churning, segmentation
Digestion (chemical)
Series of catabolic steps in which complex food molecules are broken down to their chemical building blocks - enzymes, acid, bile, etc.
Absorption
Passage of digested end products from the lumen of the GI tract through the mucosal cells into blood or lymph.
Defacation/elimination
Eliminates indigestible substances from the body via the anus as feces.
Peristalsis
Alternating waves of contraction and relaxation of muscles in the organ walls. Esophagus, stomach, small/large intestine.
Segmentation
Nonadjacent segments of alimentary tract alternately contract and relax moving food forward and backward.
Digestive activities are triggered by? Detected by?
Mechanical and chemical stimuli (i.e. stretching of organ by food, osmolarity, pH). Detected by: mechanoreceptors and chemoreceptors.
What activities do the mechanoreceptors/chemoreceptors produce when stimulated?
- Activate/inhibit glands to secrete digestive juices or hormones. 2. Stimulate smooth muscle of GI tract walls.
What are the controls of digestive activity?
Neural mechanisms, Hormonal, Local
Neural mechanisms of control?
ENS - as many neurons as the spinal cord, as many neurotransmitters as the brain. Includes submucosal plexus and myenteric plexus.
Short reflexes - local mediation, control smooth muscle contraction and glandular secretion as relatively localized activities involving small segment of the digestive tract. Sensory neurons/motor neurons/interneurons for local reflexes that operate outside the CNS.
Long reflexes - involve interneurons/motor neurons of CNS, provide a higher level of control over digestive and glandular activities.
Hormonal mechanisms of control?
As many as 18 hormones affecting almost every aspect of digestive function.
Local mechanism of control?
Involves prostaglandins, histamine and other chems released into the IF and affecting adjacent cells.
- Describe the location of the peritoneum.
Location: visceral layer covers external surfaces of most of the digestive system, parietal lines the wall of the abdominpelvic cavity.
- Describe the function of the peritoneum.
Reduce friction
Mesentery
A double layer of peritoneum that extends to the digestive organs from the body wall.
Provides routes for blood vessels, lymphatics and nerves to reach the digestive viscera.
Holds organs in place.
Stores fat.
Mostly dorsal, some ventral attachments
Some individual mesenteries?
Greater omentum, lesser omentum, falciform ligament, mesentery proper, mesocolon.
- Define retroperitoneal.
Found outside (posterior) to the mesentery, lying against the dorsal abdominal wall.
- Name the retroperitoneal organs of the digestive system.
Most of duodenum, pancreas, ascending/descending colon, rectum.
