Ch23 - Digestive System Flashcards
(36 cards)
Name the five essential activities in digestive processes
- ingestion - eating
- propulsion and mixing - peristalsis and segmentation
- digestion - Chemical and physical breakdown of polymers
- absorption - the movement of monomers across a cell membrane and into blood
- elimination - defecation
What are the three control mechanisms of digestion
- Receptors - Mechanoreceptors(stretch) and Chemoreceptors (osmolarity and pH
- Extrinsic control (outside the system) - Neural (long reflexes involving the CNS) and Hormonal (Endocrine glands secrete hormones that affect activity)
- Intrinsic Control (inside the system) - Neural (short reflexes of ‘gut brain’ respond to stimuli in GI tract) and Hormonal (enteroendocrine cells stimulate target cells in the same or different digestive organs)
Describe the peritoneum of the abdominal cavity
Parietal layer lines body wall
Visceral layer covers the abdominal organs
The cavity between the parietal and visceral layer is filled with serous fluid that acts as a lubricant
Describe the mesenteries and their function
Extensions of the peritoneal membrane’s
- anchor organs to the body wall
- Carry blood and lymph vessels and nerves fibers
- Store fat
(EXAM) compare/contrast the location of digestive system organs. Intraperitoneal and retroperitoneal
Intraperittoneal - organs are inside the peritoneal cavity (most of the organs within the DS)
Retroperitoneal - organs like posterior to the peritoneum and are embedded in the body wall. The posterior surface is covered by adventitia
Name the two blood supply systems Of the digestive system
Splanchnic circulation - hepatic, splenic, left gastric, mesenteric arteries
Hepatic Portal System - carries blood from DT to the liver for processing of nutrients
Name the four basic layers (tunics) of the digestive tract walls and their main function
- mucosa (inner most) - carries out digestion and absorption
- submucosa (2nd innermost) - supplies mucosa with blood, lymph vessels, nerves.
- Muscularis extrena (2nd outermost) - smooth muscle w/ inner/outer layers, responsible for peristalsis and segmentation (EXAM). Also contains the myenteric nerve plexus ‘gut brain’
- Serosa (outermost) - Visceral peritoneum. Joined to mesenteries and anchor the organs. produces serous fluid. ADVENTITIA covers retroperitoneal organs
Describe the enteric nervous system of the DT
intrinsic nervous system within the digestive tract with 2 nerve plexus
1. submucosal nerve plexus in submucosa regulates glands and smooth muscle in the mucsoa
2. Myenteric nerve plexus in the muscularis externs that controls GI tract motility/contraction
Linked to the CNS via sympathetic (inhibit digestion) and parasympathetic fibers (stimulate digestion)
what does the mucosa in the mouth do
Protection against abrasion and releases defensins when damaged
What does the hard palate in the mouth do
Tongue forces food against this hard structure to assist in forming a bolus
What does the soft palate in the mouth do
Uvula blocks nasopharynx doing swallowing
What is the function of the tongue and the four types of papillae
It moves and mixes food with saliva to form a bolus. Initiate swallowing speech and tasting
4 types of papillae on Tongue are
1. filiform papillae - smallest and not involved in tasting. rough surface
2. fungiform papillae - reddish, scattered. have taste buds
3. circumvallate papillae - V-shaped row in back of tongue. have taste buds
4. foliate papillae - on the lateral aspect of the posterior tongue. have taste buds
Describe the intrinsic and extrinsic salivary glands
intrinsic - (buccal glands) small and scattered in mucosa
extrinsic - large paired glands that empty saliva through ducts (parotids, submandibular, and sublingual)
Describe the composition of saliva
pH 6.75-7.00
mostly water w/ions (Na, K, Cl, PO4)
Salivary amylase (ENZYME)
small amounts of metabolic waste (urea, uric acid)
Describe the function of saliva
cleans mouth, dissolves chemicals, helps moisten and form BOLUS. Contains SALIVARY AMYLASE and releases protection against bacteria (antibody IgA)
3 Types of teeth
Incisors (I) - chisel shaped for cutting
Canines (C) - fanglike teeth that tear or pierce
Premolars (PM), Molars (M) - broad crowns for grinding/crushing
NOTE: 20 deciduous teeth, 32 permanent teeth
What are the dental formulas for teeth
2I, 1C, 2PM, 3M
General structure of teeth (outer to inner)
enamel - dentin - pulp cavity - pulp - root canal
Describe the role of the pharynx in digestion
To skeletal muscle layers contract to move food to the esophagus by peristalsis
Describe the role of the esophagus in digestion
A 10 inch tube connecting the laryngopharynx to stomach
it has 2 sphincters: Upper esophageal (closed except during swallowing) and Gastroesophageal (prevents back flow from stomach)
Describe the structure of the esophagus wall
upper 1/3 is skeletal muscle involved in conscious control (swallowing)
lower 1/3 is smooth muscle involved in unconscious control (peristalsis)
middle 1/3 is a mixture of both
NOTE: Has Advantitia instead of serosa and anchors to surrounding tissues
describe the 2 phases of deglutition (swallowing)
Buccal phase - voluntary control (act of swallowing)
Pharyngeal-esophageal phase - involuntary control - peristalsis of bolus into stomach
histology of stomach walls and 4 types of cells within
The stomach has a third muscularis externa layer - circular, longitudinal and OBLIQUE
Gastric pits and gastric glands release and produce gastric juice
FOUR types of cells:
-Parietal cells - produce intrinsic factor and HCl - activation of pepsinogen
-Cheif cells - produce the inactive enzyme pepsinogen. HCl and pepsinogen form pepsin, which begins protein breakdown
-Enteroendocrine cells - release enteric hormones into blood which regulates gastric activity
-Mucous Neck cells - produce a thin acidic mucus
How does the stomach protect against self digestion
mucosa produces a thick layer of alkaline mucus and the stem cells at entrance to gastric pits undergo rapid mitosis (3-6days)
Pepsinogen is released in its inactive form which prevent self digestion of cells.
