Digestive Flashcards
What are the functions of the digestive system
Ingestion
Mechanical processing
Digestion
Secretion, fluid, enzymes
Absorption
Excretion
What are the major divisions of the digestive tract
Mouth, mechanical, salivary
Pharynx
Oesophagus
Stomach, chem breakdown, mechanical
Small and large intestine, enzymes and absorption
What are the accessory organs of the digestive system
Salivary glands
Liver, secretes bile
Gall bladder, bile stored
Pancreas, secrete buffers and enzymes
What is the peritoneum
Has a serous membrane
- visceral layer covers organs
- parietal layer lines cavities
Peritoneal fluid
- 7 L per day produced, provides lubrication to allow sliding
What are the mesenteries
Suspend portions of the digestive tract
Allow passage of blood vessels, nerves and lymphatic vessels
What are the functions of the digestive tract
Protect against
Digestive acids and enzymes
Mechanical stresses
Bacteria
What are the layers of the digestive tract
Mucosa - inner
Submucosa
Muscularis externa
Serosa
What are the folds in the digestive tract
Plica circulares
Allow expansion and increase SA
Explain the mucosa
Mucosal epithelium
(Replaced rapidly)
- stratified squamous in oral cavity, pharynx and oesophagus
- simple columnar with mucus cells everywhere else
Lamina propria
- areola with blood, lymphatic vessels and nerve endings
Muscularis mucosae
- inner circular layer
- outer longitudinal layer
Explain the submucosa
Layer of dense irregular connective tissue
Has large blood vessels and lymphatic vessels
May contain exocrine glands
Submucosal plexus- neural network, inner area mucosa and submucosa
Explain the Muscularis externa
Smooth muscle cells
- inner circular layer
- outer longitudinal layer
Movement connected by enteric nervous systems
- sensory neurons, interneurons, motor neurons
- mainly controlled by parasympathetic
Explain the serosa
Serous membrane covering Muscularis externa, replaced by adventia (dense collagen) in upper system and rectum to stop sliding
Explain movement of digestive materials
Rhythmic cycles of smooth activity controlled by pacesetter cells
Peristalsis - waves of muscular contraction
Segmentation- cycle of contraction, mix content
Explain the role of the oral cavity
Functions
Sensory analysis
Mechanical
Lubrication
Limited digestion, salivary enzymes, carbohydrate. Lipids
Opens to nasopharynx
Explain the salivary glands
1-1.5 L per day
Water, electrolytes, buffers, mucins, antibodies
- lubricants
- dissolving chemicals
- initial digestion
Explain the process of swallowing
Buccal phase, push to back of mouth by tongue
Pharyngeal phase, epiglottis pushed back, close trachea
Oesophagus
Stomach
Explain the oesophagus
- resting muscle tone at top prevents air going in stomach
- adventitia anchors to surrounding structures
Mucosa has thick stratified squamous epithelium for protection
Explain the functions of the stomach
- store
- mechanical
- chemical breakdown:
Pepsin - protein
Salivary amylase and lipase
Acid reduces to ph2
Production of intrinsic factor
- absorption of vit b12
Explain the structure of the stomach
Fungus - top
Body pylorus
Pyloric sphincter - ring of muscle closing off exit
Muscular layers
Oblique muscular - overlying mucosa
Circula layer
Longitudinal muscle layer
Folds, rugae
Expand
Explain the stomach lining
Simple columnar
Produces mucus
- Mucosa
Gastric pits connect gastric glands in mucosa
Mucus epithelium
Lamina propria - Submucosa
- Muscularis externa
Oblique and circular muscle
Longitudinal muscle - Serosa
Explain the stomach glands
In fundus and body of stomach
Parietal cells
- secrete intrinsic factor and HCI
Chief cells
- secrete pepsinogin
- convert to pepsin by HCI
G cells
- secrete gastrin (increase stomach activity)
Pyloric glands
In pylorus
- produce mucus
- g cells produce gastrin
- d cells release stomatostatin inhibit gastrin release
What are the regio
Duodenum- 25cm long, neutralises chyme, receives secretion from pancreas and liver - few plica circulares small villi
Jejunum- 2.5m long, most chemical digestion and nutrient absorption, prominent plica circulares and villi
Ileum - 3.5 m long, lymphoid nodules
Explain the organisation of the intestinal wall
Villi on mucosa
Muscularis mucosae
Submucosa
Muscularis externa
Serosa
Explain intestine villi
Columnar epithelium with mucus cells - brush boarder with digestive enzymes
Lacteal - lymphatic vessel in middle
Capillary network
Explain the pancreas
Secretes pancreas juice containing enzymes:
Pancreatic alpha-amylase
Pancreatic lipase
Nucleases
Proteases and peptidases
What are the functions of the pancreas
Endocrine cells, secrete insulin and glucagon into blood
Exocrine cells secrete pancreatic juice
How does blood come to the liver
2/3 from hepatic portal vein, from other parts of digestive system
1/3 from hepatic artery proper
How does blood come to the liver
2/3 from hepatic portal vein, from other parts of digestive system
1/3 from hepatic artery proper
How does the liver filter and remove toxins
100,000 hexagonal lobules, functional units
Each has a portal area
- branches of hepatic portal veins and hepatic artery proper
- branch of bile duct
Blood from intestines past hepatocytes absorbing solutes and proteins
Drains into sinusoids - central vein
Bile ductules- bile ducts
What are the function of the liver
Metabolise carbs, lipids and amino acids
Remove ammonia and toxins
Vitamin and mineral stores
Drug inactivation
Haemoyological regulation;
Synthesise plasma protein
Remove circulating hormones, antibodies and toxins
Bile production
Emulsify lipids to increase SA for enzyme digestion
How is bile transported and stored
Secreted by liver
Stored and concentrated in gal bladder
Break apart lipids
Duodenal ccl release triggers gall bladder contraction- bile ejected
What are the 4 colons of the large intestines
Ascending
Transverse
Descending
Sigmoid
What connects small to large
Ileum
What are the functions of the large intestine
Absorption, less
Reabsorbtion of water and bile salts
Vitamins and organic wastes
Site of bacterial vitamin production, K, biotin and b5
Compact intestinal contents to faeces + storage
Explain wall of large intestine
Lack villi
Abundant mucus cells
Longitudinal layer of Muscularis externa taeniae coli
Explain neural control of intestinal movement
Local reflexes:
Respond to stretch and ph change
Central control:
Symp/para
Central gastric reflexes:
The gastroenteric reflex - stimulate motility and secrete in small
Gastroileal: triggers opening of valve between small and large
Explain hormonal control
Gastrin
Gip(inhibits gastrin)
Secretin and cck
Vip
How are carbs broken down
Oral cavity - salivary amylase
Stomach - di and triscaccarides
Small - pancreatic alpha amylase (di and tri)
Intestinal mucosa - monosaccharide (brush borders)
Diffuse into capillaries in villi
How are carbs broken down
Oral cavity - salivary amylase
Stomach - di and triscaccarides
Small - pancreatic alpha amylase (di and tri)
Intestinal mucosa - monosaccharide (brush borders)
Diffuse into capillaries in villi
How are lipids broken down
Lingual phase in mouth
Small intestine- bile and pancreatic lipase concert to monoglycerides and fatty acids
Diffuse through mucosa
How are proteins broken down
Polypeptides in stomach
More in small intestine to amino acids
Amino acids go to capillaries
Which nutrient dosent pass through liver before entering circulation
Fatty acids
