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digestive system


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[Front]


organs part of alimentary canal
[Back]


mouth esophagus,small & large intestine

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digestive system - Details

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Organs part of alimentary canal
Mouth esophagus,small & large intestine
Organs part of accessory organs
Tongue, liver, partotid gland,gallbladder, stomach, pancreas
8 activities of the digestive system
Swallowing, chewing, moving, churning, discharge, breakdown, taking in, defection
What is segmentation
Part of physical digestion: alimentary tract organs alternately contract and relax, churning or mixing contents
Distinguish between segmentation and peristalsis
Peristalsis-adjacent segments of alimentary tract, moves contents along tract segmentation- non adjacent segments of alimentary tract, mixes contents
Function of mucosa
Lines lumen, secretes,absorbs small intestine, protects
Function of muscularis mucosa
Produces local movement
What is found in submucosa
Dense connective tissue, lymphatic vessels, capillaries and blood vessels
What are the effects of the sympathetic and parasympathetic ANS on the submucosal plexus and the myenteric plexus?
Parasympathetic- relaxes sphincters stimulates contraction and secretion sympathetic- inhibits contractions/secretions and constricts blood
Type of mucosal epithelium found in each section of the alimentary canal
Mucosa - simple columnar epithelium w/ goblet cells
What parts of the alimentary canal have modifications in the muscularis externa
Proximal esophagus is skeletal muscle. stomach has 3 layers of smooth muscle instead of 2
.- List the components of the local reflexes of the GI tract
Interoreceptors- chemoreceptors and stretch receptors enteric motor neurons- smooth muscle contractions, glandular secretions
What types of activities of the GI tract are controlled by local reflexes?
Control of blood flow in GI, smooth muscle contractions, glandular secretions
Enteric sensory neurons:
Chemoreceptors and stretch receptors
Hirschsprung's disease
Results of missing nerve cells in large intestines that make passing stool difficult
Multiple endocrine neoplasia type 2
Rare, increases risk of having thyroid cancer, affects other endocrine glands
Symptoms of multiple endocrine neoplasia type 2
Increase levels of gastrin, ulcers, inflammation of espophagus
Acetylcholine
Parasympathetic
Norepinephrine
Sympathetic
Seotonin
Ens neurons
Secretin
Inhibit stomach activity
Histamin
Stimulate HCI secretions in stomach
Function of mesenteries
To attach to walls of abdominal cavity(hold organs)
Functions of oral cavity
Formation of bolus, ingestion mastication, mechanical/chemical digestion, deglutition
Bolus
Formation of food in mouth to go down esophagus
Chyme
Bolus with mix of stomach secretions
Function of tongue
To push bolus of food against hard palate, taste food
Primary teeth
Thin enamel, baby teeth
Permanent teeth
32, thich enamel, larger dimensions, adult teeth
Dental formula for permanent teeth
2 incisors, 1 canine, 2 premolars, 3 molars
Incisors
Chisel shaped teeth for cutting
Canines
For tearing and piercing
Premolars
Grinding/crushing
Gingivities
Inflammation of gums
Halitosis
Build-up of bacteria in mouth from gum disease ( bad breath)
Pyorrea
Ligaments and bones that support teeth become inflamed and infected
Dental caries
Tooth decay
Periodontal disease
Affects bone and supporting tissue; forms pockets between teeth
Mastication reflex
Type of stretch reflex brought by activation of muscle spindles associated w/ the mandibular jaw
Intrinsic
Scattered throughtout tongue, palate, cheek and lips
Extrinsic
Parotid submandibular sublingual
Acinar glands
Region of mouth that secretes saliva
Parotid
Secretes serous saliva into mouth, duct is above tongue and under hard palate
Submandibular
Secretes saliva (mixed serous and mucous), duct is underneath the sublingual gland ( under tongue )
Sublingual
Secretes mucous saliva,duct under tongue and lines the side of mouth
Acinar gland
Region of mouth that secretes saliva
Function of saliva
Cleanses mouth, mositen/dissolves food chemicals, aids in bolus formation
Composition of saliva
97-99% water( slightly acidic), amylase, mucin, electrocytes, lysozyme, IgA defensis
Voluntary phase
Tongue pushes bolus of food into hard palate
Pharyngeal phase
Soft palate elevated, uvula closes nasopharynx, pharynx and larynx elevates, pharyngeal constrictor muscles moves bolus toward esophagus, epiglottis pushes downward closing glottis
Esophageal phase
Bolus of food is moved by peristalsis toward stomach
Describe the histological characteristics of the esophagus.
Mucosa- stratified squamous epithelium, submucosa- areolar connection tissue, lumen- opening center, muscularis externa- longitudinal layer (distal lumen) circular layer(next to longitudinal)
Gross anatomy of esophagus
Posterior to trachea, crosses diaphragm, 2 sphincters; upper and lower(cardiac or gastroesophageal sphincter)
What is the epithelial muscosa of the stomach
Layer contains glads and gastric pits, simple columnar epithelium w/ numerous goblet cells
Rugae
Folding of mucosa and submucosa layers. non-permanent folds
Function of stomach
Storage and mixing of foods. digestion of proteins
What are the sphincters of the stomach
Pyloric and gastroesophageal
Function of HCI
Kill bacteria, denature proteins, activates pepsin, deactivates salivary amylase
Cephalic phase
Duration; short, purpose; prepares for arrival of food, stimuli; exteroreceptors- sight taste smell, control; CNS control in medulla, secretions; ACH-gastrin-pepsinogen-HCI-histamin
Why are drugs that block histamine secretion used to control HCI secretion
Because histamin has the greatest effect on HCI secretion
Gastric phase
Stimulus; presence of food and undigested proteins, duration;long,purpose; secretions used to break down food(proteins), mix, acidify, control; CNS and ENS; secretions; gastrins stimulates parietal and cheif cells, parietal cells secrete HCI and intrinsic factor, chief cells secrete pepsionogen, hisamin stimulates parietal cells secretion of HCI
What happens to acid secretions when the stomach ph reaches 2
They stop to prevent excessive HCI secretions
Intestinal phase
Duration; long, purpose; chemical digestion of foods in the duodenum,moves food to duodenum, where food will be digested.secretin and CKK will trigger pancreatic enzymes an bile secretion, while inhibiting the gastric phase by stopping gastrin secretion in stomach, stimuli; entrance of small volume of acidic chyme into duodenum, secretions; secretin and cholesystokinn hormones, control; enterogastric reflex-from CNS, ENS
What is the enterogastric reflex
Relex of duodenal contents into stomach, ph of 3-4 or 1.5
Peptic ulcers
Opens sores that develop on the inside lining of stomach. occurs when stomach acids damages the lining due to pylori bacteria
Hypertrophic pyloric stenosis
Blockage of the passage out of the stomach due to thickening of the muscle at the junction between the stomach and intestines
Gastroesophageal reflux disease
When stomach acid or bile irritates the food pipe lining. occurs when the sphincter at the lower end of esophagus relaxes at the wrong time
Pyloric pump
Empties contents of the stomach into duodenum
Mixing waves
Are weak peristaltic waves that start at the upper stomach and into antrum
Peristalic waves
Are stronger to push food through the pylorus into duodenum
The parts of small intestine
Duodenum jejunum, ilium
What features of the small intestine are adaptations that increase surface area?
Folds of the mucosa and submucosa come together w/ villi and microvilli
What features of the small intestine are adaptations that increase surface area?
Large surface area allows for more food and nutrient absorption