Digestive system Flashcards
Organs of the Digestive system
mouth, pharynx, esophagus, stomach, small and large intestines, rectum and anus.
Associated with the alimentary tract are the following accessory organs: salivary glands, liver, gallbladder, and pancreas.
Gastrointestinal Tract
GI
Long tube that is open at both ends for the transit of food during processing
Includes esophagus, stomach, small intestine, large intestine and rectum
Accessory structures
Not part of the GI tract but they do contribute to food processing
Teeth, tongue, salivary glands, liver, gall bladder and pancreas
6 processes involved in digestion
- Ingestion:taking food into the mouth
- Secretion:release of water, acid,buffers,and enzymes into lumen of GI
- Mixing and propulsion:churning movement of food though GI tract
- Digestion: mechanical and chemical breakdown of food
- Absorption: passage of digested products from GI tract into the blood and lymph
- Defecation: elimination of feces from GI tract
Layers if the GI tract
Inner to utter
Lumen
Mucosa- Epithelium, gland mucosa, lamina propria mucosa associated lymphatic tissue, muscular mucosae
Submucosa- glands of submucosa
Muscularis- circular muscle, submucosal plexus, longitudinal muscle
Nerve
Artery
Serosa- Areolar connective tissue, epithelium
Enteric Nervous system
Submucosal plexus
Myenteric plexus
Automatic Nervous system
parasympathertic
Sympathetic
Gi Reflex Pathway
GI reflex pathways regulates GI secretion and motility in response to stimulate with GI tract
Peritoneum
The largest serous membrane in the body
Mouth and parts
Formed by the cheeks, hard and soft palates and tongue
Salvary glands
Lie outside the mouth and empty their contents into ducts which deliver saliva into the oral cavity 3 pairs: Parotid Submandibular Sublingual
Tongue
Forms the floor of the oral cavity
Composed of skeletal muscle covered with mucous membrane
participates in chewing, swallowing and speech
Upper and lateral surface covered with papillae, some of which contain taste buds
Mechanical digestion
Chewing mixes food with saliva and forms a bolus which can be easily swallowed
Chemical digestion
Salvary amylase converts polysaccharides to disaccharides
Pharynx
Funnel shaped tube that extends from the internal nares to the esophagus posteriorly and the larynx anteriorly
Composed of skeletal muscle and lined with mucous membrane
Esophagus
A collapsible, muscular tube that lies posterior to the trachea and connects the pharynx to the stomach
Deglutition
- Relaxed muscular in esophagus, circular muscles contract
- Longitudinal muscle contracts, relaxed muscularis
- Lower
Stomach
J shaped enlargement of the GI tract
Functions of the stomach
- Mixes saliva, food and gastric juice to form chyme
- Serves as resivoir for food before released into small intestine
- Secretes gastric juice, that contain HCI, pepsin, intrinsic factor and gastric lipase
- Secretes gastrin into blood
Pancrease
Glans that lies posterior to the stomach
Produces enzymes that digest carbs,protiesn,fats and nucleic acids
Produces sodium bicarbonate
Empties its contents into the duodenum
Liver and Galbladder
Liver: makes bile important in the emulsification of fats
Gallbladder: stores bile until it is needed
Histology of the liver
Composed of hepatocytes, bile canaliculi and hepatic sinusoids
Blood supply of the liver
Nutrient-rich deoxygenated blood from hepatic portal vein
- hepatic sinusoids
- Central vein
- Hepatic vein
- Inferior vena cava
- Right atrium of heart
Functions of the liver and gallbladder
Carbohydrate,lips and protein metabolism Processes drugs and hormones Excretes bilirubin Storage Conducts bile salt synthesis Vitamin D activation Phagocytes
Small intestine
SI
The majority of digestion and absorption occurs here
Circular folds in the SI
Circular folds increase the surface area for digestion and absorption in the small intestine
Intestinal Juice
Provides a vehicle for absorption of substances from chyme as they come in contact with the villi
Brush border enzymes
Found on the surfaces of the microvilli of absorptive cells, breaks down food products
Mechanical digestion
Segmentation: localized contractions
Perstalsis: Propulsive contractions
Functions of Large intestine
- Haustral churning, peristalsis and mass peristalsis drive contents of colon to rectum
- Bacteria in large intestine convert proteins to amino acids, breaks down amino acids and produce some B vitamin and vitamin K
- absorption of some water, ions, and vitamins
- Formation of feces
- Defecation
Haustral churning
Distension reaches a certain point and the walls of the hausfrau contract to squeeze contents onward
Mass Peristalsis
A strong peristaltic wave that begins in the transverse colon and quickly drives the contents of the colon into the rectum
Absorption
The colon absorbs water, electrolytes and some vitamins
Feces
Consists of water, inorganic salts, sloughed off epithelial cells, bacteria, products of bacterial decomposition, and undigested portions of food
Defecation reflex
Rectal wall distends
Stretch receptors send sensory nerve impulses to the sacral spinal cord
Motor impulses travel back to the descending colon, sigmoid colon, rectum and anus
Longitudinal rectal muscles contract and the internal and sphincter opens
Phases of digestion
Cephalic phase: stimulates gastric secretion and motility
Gastric phase: neural and hormonal mechanisms
Intestinal phase: neural and hormonal mechanisms
Aging and the digestive system
Aging results in
decreased secretory mechanisms and motility
loss of strength and tone of digestive muscular tissue
changes in neurosecretory feedback
diminished response to pain and internal sensations
Digestive system disorders
Tooth decay periodontal diseases ulcers diverticula tumors hepatitis anorexia nervosa
