Digestive System Flashcards
what is digestion
The mechanical and chemical breakdown of food and the absorption of the resulting nutrients by the body’s cells
what are the two parts of the digestive system
Alimentary canal - muscular tube extending from the mouth and anus
Accessory digestive organs - everything else involved in the process of breaking food down in smaller molcules for absorption
How long is the Gastrointestinal tract
5-7 meters
What is included in the alimentary canal
Mouth,Pharynx,Oesophagus,Stomach,Small intestine,Large intestine,Rectum,Anus
What is included in the accessory organs
Inside - Teeth and Tongue
Outside - Salivary glands, Liver,Pancreas and Gall bladder
What are the 6 stages of Digestion
Ingestion
Mechanical digestion
Propulsion
Chemical digestion
Absorption
Elimination
What is ingestion
ingestion takes place in the mouth where food or liquids enter
What is mechanical digestion
involves chewing (mouth),churning (stomach) and segmentation (small intestine).
What is propulsion
this is include swallowing voluntary and peristalsis involuntary - esophagus,stomach,small intestine and large intestine process is where food is pushed through the alimentary canal
What is chemical digestion
uses certain enzymes to break down nutrients such as carbohydrates,proteins and fats into smaller molecules. into the lumen of the alimentary canal come from the accessory organs e.g pancreas and gall bladder.
What is absorption
The process of taking nutrients from the digestive system into the blood so they can be used in the body through the small intestine by active or passive transport
What is elimination
The removal of indigestible wastes through the anus, in the form of feces, is defecation or elimination.
What is segmentation
Happens in the small intestine it mixes food and digestive juices making absorption more efficiently due to moving food all over the walls of the intestine breaking it down further
What is peristalsis
is the contraction and relaxation of waves allowing food to go down alimentary canal
What is basic structure of the GI tract
The layers of the GI tract are broadly the same alll the away from the oesphagus to the anus but the mouth and pharyx are to function differently
What are the four layers of the GI tract
Serosa
Muscularis
Submucosa
Mucosa
What is the mucosa layer
Made up of three layers that secret digestive enzymes,hormones,mucus and absorbs nutrients. protects the alimentary canal - small intestine produce serotonin
What are the variations of epithelial tissues in the alimentary canal
Stratified sqaumous epithelium - short fat cells which are in the mouth,oesphagus,oropharynx and anal canal
Columnar - tall which is everywhere else
What is the lamina propria
it has lots of capillaries and are in the muscosa layer - absorption of nutrients
What is the mucosa associated lymphoiod tissues
Reservoirs for the immune system waiting for pathogen for when a pathogen re enters retains the genetic information
What is muscularias
two layer longitudinal and circular muslces which are used to push down the food through the process perisalsis and segmentation
What is the submucosa layer
is made up of loose areolar connective tissues binds and supports organs and to provide flexibility contains glands and blood vessels has elastic layers to allow stretches
What is the serosa
outer layer covers the abdomen and throax produce serous fluid that lubricates all the area allows for movements
What is the buccal cavity
within the buccal cavity are teeth that is used i mastication of food chewing use of tongue to probe our food with saliva to swallow into a bolus primary breaks down starch but to also lubricate.Saliva protects the inside of the mouth
Mouth features
Parotid salivary - gland lies in front of the ear
Salivary duct - opens into the cheek
Sublingual salivary gland - located under the tongue
Sub-mandibular - deep in the mouth
What are the four phases of swallowing
The bolus of food is pushed to the back of the oral cavity by pushing the tongue against the palate
What is the second phase of swallowing
The nasopharynx is sealed off and the larynx is elevated ,enlarging the pharynx to receive the food
What is the third phase
The pharyngeal sphincters contract sequentially,squeezing food into the esophagus.The epiglottis closes the trachea.
what is the fourth phase
The bolus of food moves down the esophagus by the peristaltic contractions
What is the oesphagus
The oesophagus begins at the pharynx and is posterior to the trachea. It enters the peritoneal cavity through an opening in the diaphragm, at the level of the 10th thoracic vertebra, to join the stomach.it is 25 cm long
What are the two sphincters
Upper and lower oesphageal sphincters these are a ring of muscles that surrounds the opening of teeth or tube
What is the stomach
has a muscularis externa with three layers that permits the churning motion of the stomach action. One of these layers is the longitudinal fibres’ outer layer.circular fibres in the middle layer.Opposite fibres’ inner layer Rugae are noticeable ridges and folds made of mucous membrane that appear when the stomach is empty. Mucous membranes and smooth muscles in the stomach expand when it is full, and rugae vanish, leaving the surface smooth.
What is the omenta
is a cutrain of fatty tissue that hangs down from the stomach and liver wraps around the intestine plays a role in immune response and metabolism
What is the stomach lining
lined by a simple columnar epithelium dominated by mucous cells secrets mucus whch protects the stomach lining from the acids, enzymes and abrasive materials.
What is gastric pits
are shallow depressions in the stomach lining detect food entering the stomach and comunicate with the gastric glands (partial and chief cells) produce the stomach secretion that is called gastric juice.when the churning and chemical process has taken place is called CHYME.
What are the functions of the stomach
1 - Bulk storage of undigested food
2 - Production of the hormone: triggering gastric juices secretion
3 - Mechanical breakdown of food
4 - Absorption of water, some lipid soluble drugs, and alcohol.
5 - Disruption of chemical bonds makes chyme
6 - Production of intrinsic factor – required for vitamin B12 absorption.
7 - Denaturing of pathogens
What is the small intestine
starts at the pyloric sphincter of the stomach, coils through the central and inferior part of the abdominal cavity surrounds by large intestine
What are the three parts of the small intestine
The dudenum,Jejunum and the ileum
What is the duodenum
is about 25 cm long, begins at the pyloric sphincter of the stomach and curves around the head of the pancreas
What is jejunum
The middle part of the small intestine. Upper abdomen helps to further digest food coming from the stomach mainly absorbs monosaccharides and amino aicds
What is the ileum
It absorbs any final nutrients and is the end of the small intestine lower part sits near the iliac crest of the pelvis mainly absorbs Vitamin B12
What are the function and importance of villi in the small intestine
Tiny projections on the inner surface of the small intestine which help in absorbing the digested foodit does this by trapping the chyme but the villi also has microvilli which further aid digest and surface ares
What are function of the small intestine
1.Onward movement of its contents by peristalsis
2. Secretion of intestinal juice (from the intestinal glands), which is an alkaline mucous secretion that helps in buffering the acids in the chyme.
3. Secretion of hormones that help in the digestion process.
4.Absorption of nutrients
What is the gall bladder
Is muscular and is hidden under the liver.it stores bile and within the gall bladder it becomes thicker it can develop into little stones blocks the duct
where does the secretion comes out of the gall bladder
It comes out of the common bile duct and join onto the secretions that come from the pancreas and all drain into the duodenum
What is the pancreas
produces enzymes that help to digest food, particularly protein. The endocrine pancreas makes the hormone insulin, which helps to control blood sugar levels. left hand side it releases pancreatic juice from the pancreatic duct.and is exocrine it neutralizers the chyme
What is the liver
The liver is the largest gland weighing about 1.5 kg,divided into four lobes - the large left and right lobes, and the smaller caudate and quadrate lobes.A tough connective tissue fold, the falciform ligament, marks the division between the right and left lobesextends from the diaphragm to the superior surface of the liver, helping to suspend the liver in the abdominal cavity.
What is the blood supply to the liver
The gastrointestinal tract and liver capillaries are connected via the hepatic portal system. Blood that is rich in nutrients is expelled from the digestive system and processed in the liver before being sent to the heart.
The hepatic portal vein and hepatic arteries each supply about half of the oxygen required by the liver.Of the blood that reaches the liver, 75% comes via the hepatic portal vein and the remaining 25% comes from the hepatic arteries.
What is the liver’s structure
Blood from the hepatic portal vein and hepatic artery mix in sinusoids
The Sinusoids empty into central veins,which send the blood to the hepatic vein and inferior vena cava
What is the kuppfer cells - positives
Specialized stellate macrophages,Adhere to the sinusoidal endothelium. It clears the blood of ingested bacterial pathogens that may enter portal blood from the gut and removes aged erythrocytes,acts as antigen presenting cells and Secret cytokines and chemokines
What is kuppfer cells - negatives
Kupffer cells also help repair injury to the liver but develops into scarring excess fibrous tissue ultimately leading to cirrhosis of the liver.Some triggers, including carcinogenic agents, cause kupffer cells to initiate production of collagen, a connective tissue, within the liver.
Excessive collagen and excessive scarring eventually renders the liver unable to perform its normal function.
Bile
Bile is secreted by the liver but stored in the gall bladder and ejected into the small intestine
What is Bilrubin
Bilirubin is a pigment produced during the breakdown of heme. Unconjugated bilirubin is not water soluble but binds to albumin to be carried to the liver,which then turns into conjugated which water soluble it can be transported into bile. normally excreted through urine and stool
Unconjugated bilirubin
In the unhealthy liver, not all the bilirubin is conjugated and is instead tightly bound to albumin and remains in the blood.isn’t filtered by the glomerulus and absent from urine even with raised serum levels of unconjugated bilirubin. tries to eliminate it via the skin, causing yellowing of the skin – or jaundice
Conjugated Bilirubin
Bile (mainly conjugated bilirubin) is converted to urobilinogen by intestinal bacteria.About 99% of this is excreted in faeces and 1% in urine
What is the metabolic functions of liver
1.Storage of glycogen and lipid reserves.
2.Maintenance of normal blood levels of glucose, amino acid and fatty acid.
3.Storage of iron reserves.
4.Storage of fat-soluble vitamins: A, D, K and E.
Fuctions of the Liver - PUSHDOG
Protein Synthesis
Urea Production
Storage
Hormone synthesis
Detoxification
Glucose and fat metabolism
What is the large intestine
The large intestine is appox 1,5 meters long begins at the caecum in the right iliac fossa and terminating at the rectum and anal canal within the pelvis.
What are the 4 sections of the large intestine
Ascending
Transverse
Descending
Sigmoid
What is the function of the large intestine
Absorption of water, salts, vitamins and some drugs. Vitamin K and folic acid synthesis.Mass peristalsis, pushing the contents from the sigmoid into the rectum, leading to defecation.Storage of faecal material prior to defecation.
What is the rectum
Two sphincters:
Internal sphincter- smooth muscle innervated by the autonomic nervous system
External sphincter- skeletal muscle innervated by the somatic nervous system
What is Perioneum
Largest and most complex serous membrane in the body.
Forms a closed sac lining the interior surfaces of the abdominal.
is not a digestive system organ
What is diverticulitis
Diverticular disease and diverticulitis are related digestive conditions that affect the large intestine (colon). In diverticular disease, small bulges or pockets (diverticula) develop in the lining of the intestine. Diverticulitis is when these pockets become inflamed or infected.
