Digestive System Flashcards
The Four Layers of GIT Tact
- Mucosa (inner most layer)
- Submucosa
- Muscularis Externa/Propria
- Adventia/Serosa (outermost layer)
Muscosa:
- Mucus secretion to lubricate food we have eaten
- Nutrient absorption
- Pathogen defense
- Muscularis mucosa: thin muscle layer. Has villi to increase SA to helps movement and helps likeliness of absorption to occur
- Gastric pits: secrete several things such as mucus, enzymes, acids etc.
Submucosa:
- Loose connective tissue
- Larger blood vessels
- Lymphatic vessels
- Nerves that enter and exit the submucosa
Muscularis Externa/Propria
- Segmentation & peristalsis
- Two muscular layers: aid with segmentation & peristalsis
- circular muscle
- longitudinal muscle
Adventia/Serosa (outermost layer)
visceral peritoneum
List digestive Processes:
Cephalic Phase Ingestion Propulsion Swallowing Peristalsis Segmentation Mechanical/Physical digestion Chemical digestion Absorption Defecation
Cephalic Phase:
digestion begins in brain, preps the body to begin the process of digesting food
Peristalsis:
rhythmic contraction & relaxation of different parts of the digestive tract which allows for the movement of food throughout the digestive tract.
Segmentation:
food moves backwards and forwards to increase rate of nutrient absorption
Mechanical/Physical Digetsion
there is no change to the chemistry of the food. It breaks up the food into smaller bits which then facilitates enzymes to act further -> more surface area available o enzymes to act on food
Chemical Digestion
enzymes chemically breakdown food
Absorption
nutrients are available to be absorbed. Absorption beings in the small intestine where most absorption occurs
Defecation:
removal of waste. Large intestine.
What enzymes break down Carbohydrates?
Salivary Amylase
Pancreatic Amylase
Maltase
What emzyme breaks down protein?
Pepsin, Trypsin & Peptidases
What enzymes breakdown Nuclei acids
nuclease & nucleosidase
what enzyme breaks down fats
lipase
Major Functions of Colon:
- Absorption of water
- Absorption of electrolytes
- Absorption of metabolites/vitamins produced by bacteria
- Store and eliminate indigestible food residues – defecation
Accessory Organs:
Liver
Pancreas
Gallbladder
The Liver - Accessory Organ
structural unit: lobules
brick life pattern of hepocytes
radiate from central nerve
Kupffer Cells (in the liver)
a phagocytic cell which forms the lining of the sinusoids of the liver and is involved in the breakdown of red blood cells & phagocytose bacteria & debris
Bile (from liver)
- alkaline solution
- aids in digestion (phospholipids & bile salts)
Gallbladder - Accessory Organ
- storage organ for bile & concentration of bile
Functions of the Liver and Gallbladder:
- Carbohydrate, lipid, and protein metabolism
- Processing of drugs and hormones
- Bilirubin excretion
- Bile salt synthesis
- Storage
- Phagocytosis
- Vitamin D activation
Pancreas – accessory organ:
- Is a gland that lies posterior to the stomach
- Produces enzymes that digest carbohydrates, proteins, fats, and nucleic acids
- Produces sodium bicarbonate which buffers stomach acid
- Empties its contents into the duodenum
phases of digestion
Cephalic phase: stimulates gastric secretion & motility
Gastric phase: neural & hormonal mechanisms
Intestinal phase: neural & hormonal mechanisms
Mouth - functions:
Ingestion of food Mechanical digestion Chemical digestion Moistens and lubricates food Some antimicrobial activity
Pharynx - functions:
Propulsion of food
Oral cavity -> esophagus
Lubrication
Esophagus - function:
Propulsion of food
esophagus -> stomach
Lubrication
Stomach - function:
Mechanical digestion
Chemical digestion
Antimicrobial function
Small Intestine - function:
Absorbs breakdown products of carbohydrates, proteins, lipids, and nucleic acids, along with vitamins, minerals, and water
Performs mechanical digestion via segmentation
Large Intestine - function:
Absorbs most residual water, electrolytes, and vitamins, produces by enteric bacteria
Propulsion and elimination of faeces
Rectum -> external environment.
Faecal matter concentration & temporarily storage
Mucus secretion for ease of faecal matter passage
