Gastrointestinal system Flashcards
What is the histology of the GI tract?
LUMEN -> MUCOSA (membrane lining the GI tract which secretes mucus ) -> SUBMUCOSA (connective tissue layer which contains blood vessles, lumph vessles and nerves)-> MUCULARSIS (smooth muscle + one circular longitudinal muscle) -> SEROSA(connectiive tissue which secreates fluid outside of the GI tract)
What are the main structures in the GI/ digestive tract tract?
WHERE FOOD PASSES THROUGH THE BODY - Oral cavity// tongue// Pharynx (“passageway from head and neck involved in both respiratory and digestive system)// Oesophagus //Stomach
// Small intestine //Large intestine
Rectum/ anus
What is the epithelium of the pharynx?
Ciliated pseudostratified columnar epithelium (nasopharynx)// moist stratified squamous epithelium (oropharynx and laryngopharynx)
What is the function of the large intestine?
reabsorb water // compacts intestinal contents into faeces// absorbs vitamins / stored feacel material // house >700species of bacteria
What is the lining of the oesophagus?
moist stratified squamous epithelium
What is the function of the peritoneal folds (mesenteries)?
connects organs to each other or to the abdominal wall
What are the 3 sections of the small intestine?
Duodenum (c-shaped found at adjacent to the pancreases at the start of the small intestine )// jejunum (connects duodenum to ileum )// ileum (extends into large intestine)
What are 4 simple columnar epithelium types which cover the villi of the small intestine and their function?
ABSORBATIVE -> digestive enzymes // GOBLET -> mucus // GLANULAR OR PANETH -> lyozomes // ENDOCRINE -> hormones
What are the main segments of the large intestine?
CECUM -> COLON (ascending limb-> transverse colon -> descending colon -> sigmoid colon ->)RECTUM = ANAL CANAL
What is the epithelium lining of the large intestine ?
MUCOSA - simple columnar epithelium // no villi or plicae// this mucosal lining is formed into straight tubular glands (crypts)
What is a plicae?
a fold or wrinkle within the epithelial tissue
What are the two sphincters of the anal canal?
internal anal sphincter (involuntary ) and external anal sphincter (skeletal muscle) // it is the circular layer of muscoularis which thickens to form these structures
what is a sphincter ?
A ring-shaped muscle that relaxes or tightens to open or close a passage or opening in the body
What are the main sphincters within the GI tract?
Upper oesophageal sphincter // pyloric s// ileocecal valve // internal anal sphincter
What makes up the oral cavity?
boundaries / cheeks /lips / palate and tongue
What is an ion dependent carriers?
protein channel/ carrier which transports molecules dependent ion concentrations
Describe secondary active transport?
Alike primary active transport, uses ATP, portein channels and electrochemical gradients // Unlike primary channels it also uses cotransporters
What is meant by absorption ?
Small molecules move through an epithelial barrier into underlying blood or lymphatic vessels
What is the difference between both secondary and primary active transport?
BOTH - ATP hydrolysis // carrier protein // uses electrochemical gradient //// ONLY SECONDARY ACUVE TRANSPORT uses cotransporters
Where does the majority of absorption occur in the GI tact ?
90% in small intestine( small inetsine -> blood -> lymph vessle)
What is the difference between a carrier and cotransporter protein?
CARRIER - transports one molecule at a time // COTRANSPORTER- transfers two molecules at a time
What does the NA+ /K+ ATPase on the basolateral membrane move?
3NA+ inside the cell for every 2K+ out
What are the two types of carbohydrates?
POLYSACCHARIDES- long chain monosaccharides/ can be digestible (starch ) or non digestible (fibre) sources = rice, pasta, cereal/// SUGARS - shorter chain found in fruits, vegetables and dairy
Where is carbohydrates broken down in the GI tract?
MOUTH - saliva breaks down starch to maltose // PANCREASE - pancreatic enzymes breaks down starch to maltose // small intestine microvilli converts oligosaccharide (saccharide polymer containing many monosaccharides) to monosaccharides
Where is protein broken down in the GI tract?
STOMACH - pepsine (a digestive enzyme) breaks proetin down into smaller polypeptide chains // PANCREAS- Trypsin, chymotrypsin, carboxypeptidase all break down proteins into smaller peptide chains // SMALL INTESTINE MICROVILLI - Specific peptidases produce tripeptides, dipeptides and amino acids
Give some examples of lipids?
triglycerides, phospholipids/ cholesterol/ steroids/ fat-soluble vitamins
Where in the GI tract are lipids broken down?
MOUTH -lingual lipase digests 10% of lipids// STOMACH - gastric lipase // PANCREASE via pancreatic lipase
*LIPASE is a digestive enzyme which breaks down triglycerides into monoglycerides and fatty acids
How does oxygen, sodium, glucose and fatty acids diffuse across a membrane?
OXYGEN - simple diffusion
SODIUM- facilitated diffusion
GLUCOSE- facilitated diffusion
FATTY ACIDS - simple diffusion
What is emulsification?
Breaking down of large lipid droplets into smaller droplets to increase their surface area
What is a vitamin?
Organic substance which cannot be manufactured by the body
What makes up chylomicrons?
90% triglycerides/ 5% cholesterol / 4% phospholipids/ 1% proteins
Describe the process of fats being broken down and absorbed by the lymph vessels ?
- fat globules are emulsified by bile in duodenum // 2. Digestion of fats through pancreatic enzymes lipase produce fatty acids and monoglycerides // 3. fatty acids and monoglycerides associate with micelles which transport them to the intestinal mucosa //4. fatty acids and monoglycerides leave micelles and diffuse into epithelial cells, these are recombines and packaged forming chylomicrons // 5. Chylomicrons exit epithelial via exocytosis -> they then enter lacteals and are carried away within lymphs
What are the two main types of vitamins ? How are they transported?
FAT -SOLUBLE -> A,D E , K , transported via micelles and diffuse into absorptive cells / WATER-SOLUBLE -> C, B absorbed by passive or active transporters
What monosaccharides require energy for absorbtion?
Glucose and galactose
-also means they can be transported against the concentration gradient
What are the secretions of the salivary glands?
lubricating fluid containing enzymes which break down carbohydrates //
What are the secretions of the stomach?
acid/ pepsin / gastric lipase
What are the secretions of the pancrease?
exocrine cells secrete buffers and digestive enzymes// endocrine secrete hormones// pancreatic juice (water + bicarbonate) // ENZYMES - > pancreatic amylase / pancreatic lipase / ribonleoase / deoxygribonucelase
What are the secretions of the liver and gallbladder?
bile
What are the secretions of the intestine?
digestive enzymes
Provide an overview of the control of digestive system secretions.
- CEPHALIC PHASE -> mouth and stomach prepare for food// . GASTRIC PHASE - > food enters the stomach and moves into duodenum (pH and stretch is detected) // 3.INTESTINAL PHASE -> food enters small intestine and pyloric sphincter contract
What are the functions of GI secretions?
chemical digestion/ lubrication / signalling / protection/ activation of enzymes / excretions of waste
What is the difference between exocrine and endocrine glands?
EXOCRINE -> Produce and secretes substances onto a epithelial surface by way of duct// ENOCRINE -> secretes hormones directly into blood
What is the components of saliva?
99.4% water // mucins// electrolytes// antibodies// enzymes - amylase
What is saliva function?
BUFFER - ions keep pH aprox 7 // keeps mucosa moist -> protects against mechanism damage and essential speech // solvent -> dissolves chemicals in food to aid detection by taste receptors
What are the two main gastric gland cells?
PARIETAL CELLS - secretes intrinsic factor// needed for absorption of B12 vitamin // secretes HCL // CHIEF CELLS -> secrete pepsinogen (which breaks certain peptide bonds) // secrete gastric lipase // MUCOUS CELLS -> secretes mucus (forms a protective barrier + has alkaline properties)
What do the different pancreatic cells secreate?
ALPHA = glucagon (response to reduced blood glucose stimulates glycogenolysis, glucagon is broken down into glucose )// BETA = insulin (in response to increased blood glucose, allows cell utilisation of glucose)// DELTA = secreates somatostain , inhibiting gastric release
What produces bile?
Hepatocytes
What is the function of the gall bladder?
Store and concentrate bile through absorbing water and ions
What is the pyloric sphincter?
serves as a kind of gateway between the stomach and the small intestine
What is xerostomia ?
Sensation of dryness in the mouth //
What pH is needed to activate pepsinogen?
LOW
How much does the liver weight?
1.5KG
Where is the liver located?
Sits underneath the diaphragm and protects the rib age// located in upper right quadrant of the abdomen
What is the blood supply of the liver?
HEPATIC ARTERY (smaller)-> from coeliac trunk of aorta, rich in oxygen // HEPATIC PORTAL VEIN (larger)-> convergence of veins draining the GI tract, rich in nutrients
What is the major functions of the liver?
bile production// detoxification// storage // nutrient metabolism // phagocytosis // synthesise of blood components
What is the role of the falciform ligament ?
Separates larger right lobe of liver and smaller left lobe
What is the visceral surface?
Inferior view of the liver (oppressions are found due to other organs resting on it)
What is the porta hepatis?
Main site where structures enter and leave the liver // CONSISTS OF - hepatic artery , hepatic portal vein
What is the role of the hepatic vein and hepatic portal vein?
HEAPATIC VEIN DRAINS THE LIVER /// HEPATIC PORTAL VEIN SUPPLIES, delivers nutrients and toxins for processing and hormone signalling
What are hepatocytes?
epithelial cells in the liver // contain many chemical transformation factories (lots of organelles e.g. mitochondria and RER.)// Space of Disse separates sinusoids and hepatocytes
What is the function of satellite cells? Where are they located?
- Inactive in healthy conditions// Cause fibrosis in disease states// Store vitamin A and produce collagen when activated// located in space of disse
What is the function of Kupffer cells ? Where are they located?
In sinusoids// specialised macrophages// Form part of the reticuloendothelial system which breaks down red blood cells (RBCs)
What is a sinusoids ?
Specialised capillaries (large and low pressure vessles) where blood from the hepatic artery and hepatic portal vein enters the liver
What type of epithelium is present in sinusoids?
fenestrated endothelium to facilitate transfer of metabolites between plasma and hepatocytes
What are the 3 stages of drug metabolism and detoxification?
1.MODIFICATION - within smooth endoplasmic reticulum reactive polar groups (metabolites) are added via oxidation, reduction and hydrolysis preventing free diffusion across a membrane// 2.CONJUNCTION - ionised group is added making the metabolite more water soluble= facilitating transport// 3. EXCERTION = smaller metabolites are excreted by the kidneys // larger metabolites are excreted in bile
What is bilibrubin ?
yellow substance which is created during RBC break down via macrophages // bound to albumin in plasma to be transported to liver
What is the difference between bilirubin glucuronic acid and bilirubin ?
conjugated bilirubin is more soluble and can therefore be excreted by hepatocytes into biliary canaliculi
What is neonatal jaundice?
excess bilibriun in plasma at birth // pre-birth placenta is removed by mothers circulation -> after birth liver conjugates biliburinwHTwHAT
What are some other functions of the liver?
Carbohydrate metabolism // lipid metabolism // protein metabolism
What is the macroscopic anatomy if the renal system?
two bean-shaped kidneys, each with a distinct outer cortex and inner medulla, separated by renal columns, with the renal pelvis collecting urine from the renal papillae within the medulla, and connecting to the ureters which carry urine to the bladder
What is the microscopic anatomy of the renal system?
REFERS TO NEPHRONS // the functional unit of the kidney, which consists of a glomerulus (a capillary network) enclosed by Bowman’s capsule, followed by the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and finally, the collecting duct
What is the structure of nephrons?
Make up the cortex and medulla // functional units of kidneys // consist of renal corpuscle and renal tube
What is the function of nephrons?
remove waste from blood and produce urine
What are some hormonal controls of the renal function?
ANTI-DIURETIC HROMONE ADH - makes water move into body // stimulates insertion of aquaporin channels // is a vasopressin - constrict blood vessles , increasing blood pressure // RENIN -ANGIOTENSIN ALDOSTERINE SYSTEM -> increases blood pressure through an enzyme pathway (increases sympathetic activity , increases vasoconstriction, increases solutes in body and blood volume
What are some nervous controls of the renal function?
SYMPATHETIC - Can ↓sodium and water excretion and can ↑angiotensin II formation
What is the movement of draining through the kidney?
minor calyx -> major calyx -> renal pelvis
What are the components of bowman’s capsule?
GLOMERULUS =capillary network// - Inner visceral layer wraps around endothelial cells of glomerular capillaries// Outer parietal layer forms outer wall of capsule //Space between the 2 layers is capsular space
What is the epithelial cell of the glomerulus visceral layer?
simple squamous epithelial
What is the process of ultrafiltration?
- GOLMERULAR FILTERATION (urine is produced, water and solutes move blood plasma -> glomerular capillaries -> glomerular capsule //2. GOLMERULAR CAPSULE DRAINS INTO RENAL TUBULE -
What are the three main renal tubes ? and their function?
Within renal cortex-> Largely responsible for reabsorption of glucose, sodium and other solutes // Loop of Henle-> Extends from medulla // Counter-current multiplier/// Distal convoluted tubule-> Within renal cortex // Reabsorbs water from filtrate
What is the function of the renal tubes?
reabsorption and secretion
What is the main function of renal corpuscle?
blood plasma is filtered
What is the counter current multiple explain?
OCCURS IN LOOP OF HENLE using osmotic gradients and varying permeability throughout the tubule// 1. filtrate is isotonic to plasma // 2. moves down descending limb (water moves out)// 3. ascending limb - solutes move out of the renal tube into intratissue fluid // 5. thick ascending limb -ions leave tubule via active transport // 6. collecting duct changes water permeability dependent on hydration of the individual
