Digestive System Flashcards
Mucosa of the Alimentary Canal
Consists of three layers of tissue:
- Muscous membrane - protection, secretion and absorption
- Lamina propia - loose connective tissue which supports blood vessels and contains lymphoid tissue
- Muscularis mucosa - think outer layer of smooth muscle that provides involutions of hte mucosa laywer (ie. gastric glands and villi)
Digestive Processing of Vitamins
- Stomach - B12 absorbtion
- Small intestine - Water solualble vitamins absorbed into capillaries, fat soluable into lacteals of villi.
- Large instestine - bacteria synthesize vitamin K, absorbed in the colon
Function of saliva
- Contains amylase an enzyme which beings the breakdown of complex sugars including starches (carbs) into disaccharide maltose.
- Lubriation of food
- Cleaning & lubrication of mouth
- Non-specific defence (lysoyme & immunoglobulins)
- Taste
Intestinal Juice
1500ml produced per day.
Contains:
- water
- mucous
- mineral salts
Has a pH of approximately 7.8
The Esophagus
- Pharynx above and diaphragm below.
- Contains upper (prevents air into esophagus) and lower (prevents gastric acid into the esophagus) sphincters
Cephalic Phase
of
Gastric Juice Secretion
Occurs before food reaches the stomach.
Due to reflex stimulation of vagus nerves (parasympathetic)
Chemical Digestion in the Small Intestine
Chyme is mixed with:
- Pancreatic Juice
- Bile
- Intestinal Juice
Disgestion of all nutrients is completed.
- Carbohydrates–> monosaccharides
- Proteins–> amino acids
- Fats –> Fatty acids and glycerol
Liver
Largest gland in the body.
Totally enclosed in a layer of peritoneum.
Consists of four lobes.
- right (small) & left lobes (large)
- caudate & quadrate lobes (posterior)
Inactivation of hormones in the liver
Include: insulin, glucagon, corisol, aldosterone, thyroid and sex hormones.
Digestive Processing of Proteins
- Hydrocloric acid in the stomach (pepisnogen–>pepsin)
- Enterokinase digestion in the small intestine
- Into the blood via capillaries in the villi
Digestive Processing of Carbohydrates
- Salivary amylase in the mouth
- Hydrochloric Acid in the stomach
- Pancreatic amylase in the small intestine
- Absorption into blood via villi
Muscous Membrane
Libricates the walls of the tract and provides them from damage from enzymes.
Name the parts of the periteneum
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Accessory Organs of the Digestive System
- 3 pairs of salivary glands
- The Pancreas
- The Liver and Biliary tract
Parts of the Alimentary Canal
- Mouth
- Pharynx
- Esophagus
- Stomach
- Small Intestine
- Large Instestine
- Rectum & anal canal
Intrinsic Factor
(a protein)
Necessary for the absorption of B12 from the ileum.
Catabolism
Process of breaking down large molecules into smaller ones
Intestinal Phase
of
Gastric Juice Secretion
When partially digested food reaches the small instestine, endocrine cells in the intestine produce two hormones
Secretin
Cholecystokinin
which slow down the production of gastric juice and reduce gastric motility.
Small Intestine
Digestion of Carbohydrates
Pancreatic amylase converts all digestible polysaccharides (starches) not acted upon by the salivary amylase to disaccharides.
Anabolism
Process of building up or synthesizing large molecules from smaller ones.
Process requires ATP.
Name the Parts of the Small Intestine
Microbial Activity in the Large Intestine
Heavily colonized with bacteria which synthesize vitamin K and folic acid.
Microbes are normally harmless but can cause problems if tranferred to other parts of the body.
Gluconeogenesis
When the body makes glucose from non-carbohydrate sources such as amino acids, and glycerol
Ileocaecal Valve
Link between the small and large intestine.
Hepatic Macrophages
(Kuppffer Cells)
Found in the liver.
Ingest and destroy worn out blood cells and any foreign particles in the blood flowing through the liver.
Small intestine
Digestion of Proteins
Trypsinogen and chymotrypsinogen are activated by enterokinase –> trypsin & chymotripsin
The product of these convert polypeptides into tripeptides, dipeptides and amino acids.
Converted to active enzymes trypsin & chymotripsin when activated in the microvilli (otherwise they would digest the pancreas where they are secreted.
Elements Absorbed in the Large Instestine
- Water
- Mineral Salts
- Vitamins
- Some drugs
Name the layers of the ailmentary canal
Inside to outside.
- Muscosa
- Submucosa (w/submucosal plexus)
- Circular muscle layer (w/myenteric plexus)
- Longitudinal muscle layer
- Peritoneum
Name the Parts of the Large Intestine
- Caecum
- Colon
- Segmoid Colon
- Rectum
- Anal Canal
Small Instestine
Digestion of Fats
Lipase converts fats to fatty acids and glycerol.
Bile salts aid this process by emulsfying fats to reduce their size and increase their surface area.
Name the parts of the Digestive System
Function of the Gall Bladder
- reservoir for bile
- concentrates bile by absorbing water
- releases stored bile
Carbohydrate metabolism in the liver
Glucose is converted to glucogon for storage under the influence of insulin.
Keeps glucose levels in the blood within a normal range.
Digestive Absorption of Water
- Stomach - small amount
- Small instestine - most absorbed here
- Large intestine - remainder absorbed here
Three Phases of Gastric Juice Secretion
- Cephalic Phase
- Gastric Phase
- Intestinal Phase
Bile
Secreted by the Liver.
pH of 8
1500ml secreted daily
Consists of:
- water
- mineral salts
- mucus
- bile salts
- bile pigments (mainly bilirubin)
- cholesterol
3 layers of the pharynx
- Lining membrane (muscosa) - continuous the the lining of the mouth, stratified squamous epithelium. Allow for wear and tear of eating.
- Middle layer - connective tissue which contains blood and lymph vessels and nerves.
- Outer layer - involuntary muscles that are involved in swallowing
Glandular Secretions of the Alimentary Tract
- Saliva
- Gastric Juice
- Instestinal Juice
- Pancreatic Juice
- Bile (from the liver)
These are digestive juices most of which contain enzymes to break down food.
Absorption
The process by which digested food pass through the walls of the alimentary organs into the blood and lymph capillaries for use by body cells.
Gastric Phase
of
Gastric Juice Secretion
Gastrin secreted by enteroendrocrine cells in the pylorus and duodenum.
This passes directly into the blood.
The Gastrin in the blood which supplies the stomach stimulates the gastric glands to produce more juice.
Suppressed when pH in pylorus falls to 1.5
Hepatic Ducts
Leave the liver and carry bile to the gall bladder.
Lymph Nodes in the Small Intestine
Found in the mucosa at irregular intervals through the whole small intestine.
Packed with defensive cells which neutralize ingested antigens.
Include solitary lymphatic follicles (small nodes) and aggregated lymphatic follicles (found at the distal end of the ileum)
Digestive Processing of Fats
- Bile from the liver breaks down fats to fatty acids
- Absorbed into the lacteals of the villi in the small instestine
Location of the Gall Bladder
Attached to the rear of the liver by connective tissue.
Sympathetic Nerve Supply
- Decrease muscular activity (peristalsis)
- Decrease glandular secretion
Submucose of the Alimentary Canal
Binds the muscle layer to the mucosa.
Contains plexuses of blood vessels, nerves and lymph vessels and lymph tissue.
Pharynx
- Nasopharynx - important in respiration
- Oropharynx
- Laryngopharynx
Both 2 and 3 are common to the respiratory and digestive systems.
Function of Hydrochloric Acid in Stomach
- Acidifies food and stops action of salivary amalyase.
- Kills ingested microbes
- Provides acidic enviroment for effective digestion by pepsinogens
Propulsion
Mixes and moves the contents along the alimentary tract.
Functions of the tongue
- Chewing (mastication)
- Swallowing (Deglutition)
- Speech
- Taste
5 Main Processes of the Digestive System
- Ingestion
- Propulsion
- Digestion
- Absorption
- Elimination
Functions of the Small Instestine
- Onward movment of contents by paristalsis
- Secretion of Intestinal Juice
- Completion of chemical digestion
- Protection agains infection
- Secretion of hormones (cholecystokinin and secretin)
- Absorbtion of nutrients
Digestion
Mechanical and chemical breakdown of food.
(mastication and enzyme digestion)
Ingestion
The taking in of food into the alimentaory tract
(eating and drinking)
Parasympathetic Nerve Supply
Vagus nerve supplies most of the alimentary tract.
- Increased muscular activity (peristalsis)
- Increased glandular secretion
Peritoneum
Largest serous membrane in the body.
Is a closed sac containing a samll amount of serous fluid and is richly supplied with blood, lymph vessels and lymph nodes.
Provides a physical barrier to prevent the spread of infection.
Parietal periteneum - lines the abdominal wall
Visceral Peritoneum - covers the organs within the abdominal and pelvic cavities
Protein metabolism in the liver
Removes nitrogen from amino acids to form urea which is excreted.
Breakd down nucleic acids to form uric acid which is excreted.
Pepsinogens
Activated to pepsins by HCL and pepsins already present in the stomach.
Being the digestion of proteins, breaks them down into smaller molecules.
Name the three main salivary glands
- Parotid glands - each side of the face below the ear
- Submanibular glands - Each side of the face under the jaw
- Sublingual glands - Under hte muscous membrane in the floor of the mouth.
Production of heat in the liver
The liver uses a considerable amount of energy and has a high metabolic rate.
Is the main heat producing organ in the body.
Name the 3 parts of the Stomach
- Fundus (top)
- Body (middle)
- Pylorus (bottom)
There is also the cardiac sphincter at the top and the pyloric sphincter at the base.
Functions of the Liver
- Carbohydrate Metabolism
- Fat Metabolism
- Protein Metabolism
- Breakdown of erythrocytes and defence agains microbes
- Detoxification of drugs and toxic substances
- Inactivation of hormones
- Production of heat
- Secretion of bile
- Storage
Name the 4 parts of the Colon
- Acending Colon
- Transverse Colon
- Descending Colon
- Sigmoid Colon
Mass Movement in the Large Intestine
Aka gastrocolic reflex
Large wave of peristalsis that sweeps along the transverse colon sweeping contaents along, precipitated by food entering the stomach.
Occurs twice an hour.
Functions of the Large Intestine
- Absorption - including water, mineral salts, vitamins and drugs
- Microbial Activity - large instesting is heavily colonized with bacteria which synthesize vitamin K and folic acid. Microbes are normally harmless but can cause problems if tranferred to other parts of the body.
- Mass Movement - aka gastrocolic reflex - large wave of peristalsis that sweeps along the transverse colon sweeping contaents along, precipitated by food entering the stomach. Occurs twice an hour.
- Defaecation - Mass movement forces contents of teh sigmoid colon into the rectum.
Defaecation in the Large Intestine
Mass movement forces contents of teh sigmoid colon into the rectum.
Pancreatic Juice
Secreted by the exocrine gland of the pancreas.
Contains enzymes:
- amylase
- lipase
- nucleases (digest DNA and RNA)
Inactive enzyme precursors:
- trypsinogen
- chymotrypsinogen
Has a pH of 8
Substances Stored by the Liver
- Glycogon
- Fat soluable vitamins (A, D, E, K)
- Iron & copper
- Some water soluable vitamins (B12).
Muscle layer of the Alimentary canal
Consists of two layers of smooth (involuntary muscle).
Bwetewen the two layers or blod vessels, lymph vessels and a plexus (network) of parasympatheic and sympatheic nerves.
Contraction occurs in waves called peristalsis.
Muscle contraction mixes food with digestive juices.
Sphincters are things rinds of circular muscle which regulate forward movement of food,
Stomach Mucous
Protects stomach walls from HCl
Contents of Gastric Juice
- Water (secreted by gastric gland)
- Mineral Salts (secreted by gastric gland)
- Muscous (secreted by mucous cells in glands and surface cells on stomach wall)
- Hydrochloric Acid(secreted by gastric gland)
- Intrisinic Factor (secreted by gastric gland)
The Pancreas
Both an endocrine and exocrine gland.
Exocrine - produces pancreatic juice containing enzymes which digest carbs, proteins and fats
Endocrine - secretes insulin and glucagon which control blood glucose levels
Parts of the Large Bowel
- Ascending Colon
- Transverse Colon
- Descending Colon
- Sigmoid
- Rectum
