module 5 Flashcards
whats the six process of digestive system in order
ingestion propulsion mechanical breakdown chemical digestion absorption defection
whats ingestion
- Taking food and water into digestive tract
- Usually occurs via the mouth; involves the lips and tongue.
whats proplusion
- Moving food through digestive tract
- Starts when swallowing (initiated voluntarily)
- Peristalsis
whats peristalsis
alternate wave of muscle contraction and relaxation (involuntary) around the food. Squeeze food along the pathway. powerful
whats mechanical breakdown
- Physically breaking the food up into smaller fragments so it can be digested involves;
- Mouth; chewing and mixing food with saliva
- Stomach’ churning and mixing with gastric juice= liquid mixture
- Small intestine’ segmentation= mixes food with digestive juices and acids in nutrient absorption. Increases efficiency of absorptions and ability of enzymes to act on food
whats chemical digestion
- enzymes break down complex food molecules into their building blocks (monomers)
- Occurs in the mouth, stomach and in the small intestine
whats absorption
- Passage of end products (monomers) from the lumen of the digestive tract into te blood or lymph.
whats defection
- Elimination of indigestible substances, in the form of faeces, from the body via the anus.
what the four layers/tunics of the walls of the digestive tracts
- mucosa
- submuscosa
- muscularis externa
- serosa
whats the mucosa
the innermost layer is a moist membrane that lines the lumen from mouth to anus. As the name suggest it secretes mucus, which eases the passage of food and protects the organs from itself being digested by enzymes. This layer also secretes digestive enzymes and hormones as well as absorb nutrients that have been digested.
whats the submucosa
external to the mucosa and contains elastic tissue to allow stretch and recoil after temporarily storing a meal.
whats the muscular external
- surrounds the submucosa is composed of smooth muscle cells and responsible for peristalsis and segmentation. It forms a sphincter to ensure food travels in one direction.
whats the serosa
outermost layer that supports the digestive organs and anchors them to surrounding structures.
what do the walls of the digestive tract also have
- Blood vessels to absorb the products of digestion
- Parasympathetic and sympathetic nerves to alter motility of the digestive system
- Lymphatic vessels from lipid transport
- Lymphoid tissue for immune function
what does the mouth do
- Modified muscoa: lined by stratified, squamous epithelium (continually replaced due to absorption)
whats the digestive functions of the mouth
- Ingestion: food is voluntarily placed into the oral cavity
- Mechanical breakdown by mastication (chewing), tongue mixes food with saliva
- Chemical digestion of carbohydrates initiated by enzymes (amylase) found in saliva
- Propulsion (peristalsis)- swallowing food
what does the salivary glands do
- Produce saliva which contains mostly water, mucus, electrolytes, digestive enzymes and antimicrobial proteins.
- Functions of saliva:
- Mucus moistens and lubricates food
- Dissolves food chemicals and facilitates tastes
- Contains enzymes (amylase) that initiates chemical digestion of carbohydrates.
- Primary controlled by parasympathetic nervous system
whats the pharynx and oesophagus do
- Propulsion (peristalsis) of food to the stomach
whats special about the stomachs wall layers/tunic
- Muscularis externia; circular and longitudinal- mix, churn and propel food
- Modified contains an additional oblique muscle layer in muscularis externia= pummels the food and rams chime into the small intestine.
- Modified muscoa: the surface of the mucosa is composed entirely of mucus producing cells (goblet cells). Muscoa indented into gastric pits= gastric glands.
what does gastric pits contain
- Parietal cells; produce hydrochloric acid(HCI), activate pepsin, denature proteins and destroys most bacteria.
- Chief cells; produce pepsinogen, the inactive form of pepsin
- Goblet cells; mucus protect musoca from HCI
whats the functions of the stomach
- Mechanical breakdown- mixing food with gastric juice
- Chemical digestion of proteins initiated (pepsin)
- Absorption (minor role) of fat soluble chemicals eg alcohol, and aspirin
- Propulsion (peristalsis) to the small intestine
whast the three subdivisions of the small intestine
- Duodenum: curls around the pancreas, receives bile and pancreatic juice for chemical digestion
- Jejunum: major site of mechanical and chemical digestion and absorption
- Ileum: ends at the large intestine
whats the three structural modifications of the small intestine for nutrient absorption
- Circular folds; deep, permanmetn folds of the mucosa and submusoca. Slow the movement of chyme, thus increasing the time for nutrient absoprtion
- Villi: finger like projections of the musoca. Absorptive epithelial cells= nutrient absorption. Core contains a capillary bed and a wide lymph capillary. Contain goblet cells to produce mucus. Enterocytes produce intestinal juice.
- Microvilli: very small, densly packed on the surface of individual absorptive epthlieal cells= form the brush border. Plasma memebrane bears enzymes that complete carbohydrate, protein and nucleinx acid digestion (brush brer enzymes)
- = surface area increases more than 600 times.
whats the functions of the small intestine
- Propulsion: food moves along the tract
- Mechanical breakdown: segmentation mixes the food with digestive jucies
- Chemical digestion 4 classes; carbohydrates, proteins, fats and nucleic acids
- Nutrient absorption: nutrients absorbed into the blood (fats move into the lymph
whats the functions of the large intestine
- Absorption: water and electrolytes, vitamins produced by bacterial flora
- Propulsion; haustral contractions and mass movements
- Defaecation; parasympathetic reflex. Triggers by distension of the rectum to eliminate facese fmor the body.
- Chemical digestion: remain foods are digested by enteric bacteria
what the arlge intestine modified about the tunic
- Modified mucosa= simple epithelium; rich in goblet cells = ease the passage of faeces, protect the intestinal wall from bacterial acids and gases.
whats accessory organs of the digestive system include
liver
gall blader
pancreas
whats the function of the liver
- Produce bile from hepatocyts= collect and drain bile into the bile duct of the portal traid.
- Digestive function= production of bile
- Hematologic function= synthesis of plasma proteins
- Detoxification: alcohol
- Drug and hormone metabolism; first pass metabolism
- Metabolic functions: process of nutrients, removing and storing excess nutrients, use of amino acids to make protein or yield energy, break down fatty acids to yield energy, vitamin and mineral storage.
- Correcting nutrient defiences; regulation circulating levels of glucose, triglycerides, fatty acids and cholesterol. (Blood exiting the liver has less nutrients then entering)
- Bile breaks down fats
whats the basic anatomy of the liver
- Largest gland
- Gall bladder rests on the inferior surface of the liver
- Dual blood supply; haptic artery= oxygenated blood hepatic portal veins= nutrient rich blood
whats the location of the gall bladder
inferior surface of liver
