Digestive

Question 1

Differentiate between digestion and absorption.

Answer 1

Digestion: process of breaking down food molecules into their monomers through hydrolysis
Absorption: transport of monomers from lumen of digestive tract into blood/lymph

Question 2

List and describe the anatomy of the organs of the alimentary canal from mouth to anus.

Answer 2

Mouth: located in oral cavity; food is masticated and mixes with salivary glands to form bolus to be swallowed
Pharynx: cavity located between the mouth and the esophagus, posterior to the nasal cavity; the pharynx is involved in the deglutition process (swallowing)
Esophagus: long muscular tube that carries food boluses from the pharynx to the stomach via peristalsis
Stomach: J-shaped muscular organ; delivers chyme to duodenum; food is stored and mixes with acid and pancreatic juices to start the digestion process prior to moving to the small intestine
Small Intestine: long narrow tube between the stomach and large intestine; 3 sections: duodenum, jejunum, and ileum, and terminate at the ileocecal valve
-digestion and absorption of food molecules; to increase surface area, the mucosa of the small intestine is folded into villi, and in turn, the villi have further folds known as microvilli
Large Intestine: runs from the ileocecal valve to the anus; water and electrolyte reabsorption
-larger in diameter and shorter in length than the small intestine; doesn’t contain villi
-outer surface forms haustra (pouches); includes cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum and anal colon
Rectum: last section of the large intestine; feces are passed; it initiates the defecation reflex through increases in pressure; contains an internal and external sphincter
Anus: opening at the end of the rectum which moves feces from the rectum to the outside of the body

Question 3

List and describe the anatomy of the accessory digestive organs

Answer 3

Liver: located beneath the diaphragm and it the largest internal organ; liver is connected to the digestive tract via the hepatic portal vein and the bile duct
Gall Bladder: storage sac for bile that is closely associated with the liver and will release bile into the duodenum via the bile duct
Pancreas: glandular organ that is located behind the stomach, near the small intestine

Question 4

Describe the four tunics of the alimentary canal and indicate their functions.

Answer 4

Mucosa: lining of the lumen; composed of columnar epithelium that is supported by the lamina propria (connective tissue with lymph nodules), smooth muscle layer (muscolaris mucosae) that create the folds in the villi
Submucosa: thick, vascularized connective tissue that provides blood/lymph to the mucosa; submucosa also contains glands and the nerve plexus (Meissner’s plexus)
Muscularis: contains layers of smooth muscle used for movement of food through the digestive tract
-includes the inner circular and external longitudinal smooth muscle; main nervous supply, the myenteric plexus, is located between these two muscle layers
Serosa: outer protective layer of the digestive tract composed of connective tissue and simple squamous epithelium

Question 5

Discuss the enteric nervous system (ENS), its location and autonomic regulation.

Answer 5

ENS: large network of neurons and glial cells that innervate the digestive tract
-organized into ganglia and interconnected by 2 plexuses; Meissners plexus in the submucosa and the myentric plexus located between the circular and longitudinal smooth muscles in the muscularis
-has sensory, autonomic and interneurons that regulate digestive functions
-extrinsic control of the ENS is regulated by the autonomic nervous system through sensory extrinsic afferent neurons
-intrinsic afferent neurons deliver sensory information to the plexuses through interneurons
-extrinsic afferent sensory neurons will relay information through the CNS to the brain, where the brain can overpower intrinsic regulation through stimulation of the PSNS

Question 6

Identify the 2 plexuses that compose the ENS.

Answer 6

Myenteric Plexus (Auerback’s plexus)
Meissner’s Plexus

Question 7

Define and describe: ingestion, mastication, deglutition, bolus, peristalsis, chyme, segmentation, villi and microvilli, brush border, plicae circulares, haustra, storage, elimination.

Answer 7

Ingestion: consumption of food material through the mouth
Mastication: chewing of food into smaller pieces and mixing with saliva to form a bolus
Degultition: swallowing of food bolus from the oral cavity; the bolus travels from the mouth through the pharynx, down the esophagus and finally to the stomach
Bolus: ball-shaped mass of food that is formed in the mouth through mastication and mixing with saliva
Peristalsis: wave-like rhythmic contraction of smooth muscle that propels bolus or chyme in a forward direction
Chyme: pasty food material that is formed in the stomach and delivered to the small intestine
Segmentation: muscular contraction of the small intestine to further mix chyme
Villi: finger-like folds in the mucosa of the intestinal lumen made of columnar epithelial cells
Microvilli: folding of the apical membrane of columnar epithelial cells
Brushborder: eggs found on the surface of microvilli (facing the lumen of the digestive tract)
Pilcae Circulares: large fold formed by the mucosa and submucosa in the small intestine
Haustra: formed pouches on the outer surface of the large intestine
Storage: capacity to temporarily store food material for further digestion and/or for controlled movement through the digestive tract
Elimination: act of removing or eliminating indigestible food material from the digestive tract

Question 8

Describe the process of mastication and deglutition.

Answer 8

Mastication: act of chewing food and mixing it with saliva to form a bolus; amylase will begin to starch digestion
Deglutition: act of swallowing of food bolus; process is highly controlled and involves the use of 25 muscles; it is divided into 3 phases:
1. Oral: mixing of food to form bolus, followed by movement of bolus to back of mouth by the tongue
2. Pharyngeal: presence of food bolus triggers receptors in the oropharynx, stimulating the follow mechanisms:
a. soft palate to lift and close the nasopharynx, preventing food from entering the nose
b. epiglottis to fold over the larynx, preventing movement of bolus down the trachea
c. relaxation of esophageal sphincter, allowing movement of bolus into esophagus
3. Esophageal: bolus travels down the esophagus and finally to the stomach by peristaltic contractions

Question 9

Discuss the role of salivary glands in deglutition and digestion of carbohydrates.

Answer 9

Salivary glands release saliva that moistens food to help form the bolus that is subsequently swallowed. Saliva also contains salivary amylase to begin the digestion of starch (carbohydrates)

Question 10

Indicate the location of the swallowing centre of the brain.

Answer 10

Brain stem

Question 11

Identify the 3 phases of deglutition.

Answer 11

Oral, pharyngeal, esophageal.

Question 12

Describe the muscular composition of the esophagus on the effects on deglutition.

Answer 12

-proximal esophagus (upper third) is lined with skeletal muscle
-as you move down; mixture of skeletal and smooth muscle
-distal portion of esophagus; smooth muscle
-smooth muscle includes longitudinal muscle in the outer layer and circular smooth muscle found in the inner layer
-skeletal muscle is under voluntary control, whereas smooth muscle is controlled by the nervous system, and is involved in the movement of the bolus through peristalsis

Question 13

Discuss the process of peristalsis and how it moves throughout the alimentary canal.

Answer 13

-peristalsis is a wave-like muscular contraction that propels food in a forward direction
-involves the contraction of both circular and longitudinal smooth muscle
-contraction of circular smooth muscle behind bolus will push the bolus forward
-contraction of the longitudinal smooth muscle that shortens the tube, further propelling it forward

Question 14

Describe the lower esophageal sphincter and indicate its function.

Answer 14

Lower esophageal sphincter is a thickening of smooth muscle at the distal end of the esophagus, between the esophagus and the stomach; prevents the regurgitation of food from the stomach back into the esophagus.

Question 15

Indicate the physiological functions of the stomach.

Answer 15

1. Storage of food
2. Mixing of food
3. Controlled gastric emptying into small intestine

Question 16

Identify regions of the stomach.

Answer 16

1. Cardiac Region
2. Fundus
3. Pyloric Region

Question 17

Describe the mucosa of the stomach and indicate why its ideal for protein digestion.

Answer 17

-protein digestion requires an acidic environment which can cause damage to the muscosal lining of the stomach
-stomach mucosa provides proper acidic environment while protecting mucosal lining
-contains gastric pits that are made up of mucous, chief and parietal cells which secrete mucus, pepsinogen, and hydrochloric acid
HCL: creates acidic environment
Pepsinogen: activate and digest protein molecules
Mucus: provide protective layer on gastric epithelial surface that contains bicarbonate to neutralize acid and protect stomach lining

Question 18

Differentiate between endocrine and exocrine secretions.

Answer 18

Endocrine glands release hormone directly into the bloodstream, whereas exocrine glands release chemical substances through ducts, releasing outside the body.

Question 19

Identify the product each of the following cells make: mucous neck cells, parietal cells, chief (zymogenic) cells, enterchromaffin-like (ECL) cells, G cells, and D cells.

Answer 19

Mucosal Neck Cells: mucus
Parietal Cells: HCl
Chief Zygenic Cells: pepsinogen
Enterochromaffin-Like (ECL) Cells: histamine, serotonin
G Cells: gastrin
D Cells: somatostatin

Question 20

Discuss the role on digestion for the following cellular products: mucous, hydrochloric acid, pepsinogen, histamine, serotonin, gastrin and somatostatin, intrinsic factor, ghrelin.

Answer 20

Mucous: protects stomach from acidity of gastric juices
HCl: lowers pH of gastric juice to initiate protein digestion and kill bacteria
Pepsinogen: precursor of pepsin (enzyme for protein digestion)
Histamine: stimulates parietal cells to release HCl
Serotonin: paracrine regulator; used to control intestinal movements by activating motor neurons through the myenteric plexus
Gastrin: stimulate parietal cells to release hydrochloric acid and stimulation of ECL cells to release histamine
Somatostatin: inhibit secretion of gastrin from G cells, which in turn, reduce secretion of HCl from parietal cells
Intrinsic Factor: required for the absorption of B12 vitamin in the ileum
Ghrelin: may help regulate hunger

Question 21

Identify components of gastric juice.

Answer 21

Secretions from gastric cells (ex. pepsin, hydrochloric acid, etc.) and water

Question 22

Discuss why low pH of gastric is ideal for digestion.

Answer 22

Low pH allows for:
-denaturation of proteins; allows for better enzymatic digestion (access to peptide bond)
-activation of pepsinogen to pepsin; protein digestion (digestion/hydrolysis of protein peptide bonds)

Question 23

Describe the secretion of gastric acid by parietal cells.

Answer 23

Hydrochloric acid is secreted by parietal cells through stimulation by gastric, histamine and acetylcholine
1. At the apical membrane, H+/K+ ATPase pump will transport H+ ions against its concentration gradient into the stomach in exchange for K+
2. At the basolateral membrane, Cl- ion is transported from the blood into the parietal cell through the exchange of HCO3-; Cl- ion diffuses across the apical membrane into the stomach where it combines with H+ to form HCl

Question 24

Describe the anatomy of the small intestines and indicate relative lengths of each section.

Answer 24

-between stomach and large intestine
-divided into 3 sections: duodenum (30 cm), jejunum (2/5 length) and the ileum (3/5 of small intestine)
-longest section of the digestive tract with the smallest luminal diameter
-its mucosa is folded into villi whose membrane undergoes further folding to form microvilli

Question 25

Describe the crypt, villi, and microvilli morphology of the small intestines and how they contribute to giestion.

Answer 25

Crypt: narrow pouches of epithelium at the base of the villi that face downward; contain secretory cells (goblet cells and that will release mucus and Paneth cells that release lyososome)
Villi: folding of mucosal lining of the small intestine to increase absorptive surface area
-villi are composed of columnar epithelium that’s supported by the lamina propria, connective tissue with lymph nodules, blood capillaries and central lacteal (lymphatic vessel)
Microvilli: microscopic folds of epithelial plasma membrane; contains digestive enzymes that will hydrolyze molecules at the cell surface just prior to absorption (ex. enzyme is associated with brushborder and not secreted into lumen)

Question 26

Discuss the regenerative capabilities of the intestinal mucosa.

Answer 26

Intestinal mucosa has a rapid turnover; it can create an entire new epithelial layer within 4-5 days. New epithelial cells are formed in intestinal crypts and will migrate from the crypt to the top of the villi, where cells will eventually be shed into the intestinal lumen.

Question 27

Describe the brush border enzymes.

Answer 27

Brush border enzymes are attached to PM of enterocytes in microvilli.
-enzymes will hydrolyze molecules into their monomers prior to absorption
-includes enzymes that will cleave/activate other intestinal enzymes (ex. enterokinase will activate trypsin; a protein digesting enzyme)

Question 28

Discuss how the interstitial cells of Cajal mediate slow wave formation and their effects on smooth muscle contraction.

Answer 28

-interstitial cells of Cajal (ICC) are the pacemaker for contractions of smooth muscle in the small intestine
-ICC have long processes and are interconnected to smooth muscle by gap junctions, which spread the depolarization originating from ICC to adjacent smooth muscle
-ICC will produce graded depolarization, known as slow waves, which will cause action potentials in the smooth muscle and subsequent contraction
-slow-wave depolarization of ICC surpasses threshold -> opening of voltage-gated Ca2+ channels in smooth muscle -> influx of Ca2+ into muscle cell -> depolarization and subsequent contraction of smooth muscle

Question 29

Indicate how the autonomic nervous system impacts the interstitial cells of Cajal and its effects on motility.

Answer 29

-autonomic axons, located between smooth muscle cells in the intestine, release neurotransmitters that will modify the enteric nervous system, which will in turn stimulate or inhibit ICC
-acetylcholine will increase the amplitude and duration of slow waves, increasing motility of the small intestine

Question 30

Describe segmentation and indicate its digestive function.

Answer 30

Segmentation if a type of contraction where circular smooth muscle will contract in multiple locations at the same time. This serves to move chyme back and forth to thoroughly mix it with digestive juices and mucus.

Question 31

Describe the anatomy of the large intestine and indicate relative lengths of each section.

Answer 31

The large intestine is the distal part of the digestive tract originating from the ileocecal valve to the anus.
-it is shorter in length but larger in diameter compared to the small intestine and doesn’t contain villi
-includes the ascending colon, transverse colon, descending colon, sigmoid colon, rectum and anal canal

Question 32

Discuss the role of intestinal microbiota have on digestion.

Answer 32

In large intestine, intestinal microbiota will ferment undigested molecules and produce short chain fatty acids that:
1. supply energy to intestinal enterocytes
2. provide an energy source to the body (absorbed into bloodstream)
3. stimulate electrolyte absorption in the large intestine (Na+, Cl-) and subsequent water absorption
Microbiota will also provide B vitamins and vitamin K.

Question 33

Describe the fluid and electrolytes absorptive capabilities of the large intestine.

Answer 33

-absorption of fluid in the large intestine accounts for 90% of total fluid absorption in the digestive tract
-through passive diffusion/osmosis of water down its concentration gradient created by Na+/K+ pumps located in the basolateral membrane

Question 34

Discuss the defecation reflex.

Answer 34

Defecation Reflex: stimulated by an increase in rectal pressure due to entry of waste material into the rectum, causing relaxation of the internal anal sphincter
-external anal sphincter allows entry of feces into the anal canal and is under voluntary control
-upon individual’s decision to defecate; external sphincter relaxes
-excretion of fecal material is aided by contraction of abdominal and pelvic muscles which increases intra-abdominal pressure

Question 35

Describe the anatomy of the liver, gall bladder and the hepatic portal circulation.

Answer 35

Liver: made of hepatic plates, made of 1 or 2 hepatocytes; separated by capillary spaces (sinusoids)
-spaces are every porous due to fenestrae that have a single endothelial lining allowing passage of large molecules such as protein
Gall Bladder: pear-shaped organ attached to the liver that stores bile produced by liver hepatocytes
-bile is transported to the gall bladder from the liver via the cystic duct
-common bile duct and cystic duct will deliver bile to the duodenum
Hepatic Portal Circulation: unique system of vessels that carry blood from the digestive tract to the liver for processing and back to systemic circulation
-capillaries carry blood to the liver lobules through capillaries (hepatic sinusoids) and returned to systemic circulation via the hepatic vein

Question 36

Describe the microscopic structure of a liver lobule and indicate the functional significance of the arrangements of the central vein, sinusoids, and portal triad.

Answer 36

-liver lobules are made up of hepatic plates that are composed of one or 2 hepatocytes, separated by capillary spaces called sinusoids
-spaces are very porous due to fenestrae that allow passage of large molecules such as protein
-blood will enter the liver lobule through the portal triad, located at the periphery of liver lobules
-portal triad drains blood from the hepatic artery where they will converge and mix within the sinusoids
-both exit via the central vein located in the middle of each liver lobule
-portal triad also includes the bile ductile that carries bile away from the liver
-bile flows in the opposite direction through bile canaliculi and therefore will never mix with blood

Question 37

Trace the blood flow through the liver.

Answer 37

Blood enters the liver through vessels in portal triad (hepatic artery + hepatic portal vein) -> hepatic sinusoids -> exits via the central vein -> hepatic vein

Question 38

Discuss enterohepatic circulation.

Answer 38

Enterohepatic Circulation: circulation between intestine and liver
-recycling of bile salts and liver secretions that are delivered to the intestine via the common bile duct
-bile salts are then reabsorbed from the small intestine and returned back to the liver via the hepatic portal vein
-important for clearance of exogenous substances (drugs); liver secretes it into the bile which will drain into intestine for excretion

Question 39

List the functions of the liver.

Answer 39

1. Detoxification of blood
2. Carbohydrate metabolism
3. Lipid metabolism
4. Protein synthesis
5. Secretion of bile

Question 40

List the functions of the gall bladder and describe its connection to the alimentary canal and liver.

Answer 40

-gall bladder stores and concentrates bile from the liver
-bile is delivered to the gall bladder via bile ducts, hepatic duct and cystic ducts when the sphincter of Oddi, located at the end of the common bile duct, is closed
-upon contraction, the gall bladder will drain bile into the duodenum via the common bile duct

Question 41

Describe the anatomy of the pancreas.

Answer 41

Pancreas: glandular organ that is located behind the stomach, near the small intestine
-includes endocrine and exocrine sections
-exocrine pancreatic acini contain a layer of acinar cells where zymogens are produced, stored and secreted into the surrounding lumen before entering the pancreatic duct
-pancreas is connected to the duodenum via the pancreatic duct through which pancreatic juice is delivered
-endocrine pancreas; pancreatic islets of Langerhans produce and secrete insulin and glucagon into the blood

Question 42

Differentiate between exocrine and endocrine pancreas.

Answer 42

Pancreas has an endocrine function by secreting the hormones insulin and glucagon. Exocrine gland since it secretes pancreatic juice which contains digestive enzymes into the duodenum.

Question 43

Identify components of pancreatic juice.

Answer 43

Bicarbonate, digestive enzymes (anylase, trypsin, lipase)

Question 44

Describe the digestive enzymes of the pancreas, its substrate and products.

Answer 44

Trypsin: protein; amino acids
Lipase: tryglycerides; fatty acids
Amylase: starch; glucose

Question 45

Discuss zymogens and their activation.

Answer 45

Pancreatic enzymes are in their inactive form (ex. zymogens) while they’re stored in the pancreas to prevent digestion of the pancreas. Once pancreatic juice is delivered to the duodenum, a brushborder enzyme will activate zymogens into their active form by cleaving off a polypeptide sequence.

Question 46

Discuss the role of enterokinase and trypsin in activation of pancreatic enzyme.

Answer 46

Enterokinase: brushborder enzyme that will activate the zymogen trypsinogen into trypsin
Trypsin: will then activate other pancreatic enzymes such as chymotrypsinogen into chymotrypsin

Question 47

Identify the 3 phases of digestion and describe each.

Answer 47

1. Cephalic Phase: regulation of gastric function by the brain via the vagus nerve
   a. brain is stimulated by the presence and smell of food, whereby the vagus nerve stimulates gastric cells to secrete pepsinogen, hydrochloric acid and histamine in preparation of food
2. Gastric Phase: food enters the stomach and gastric secretions are stimulated by distension of the stomach wall and chemical composition of chyme
   a. end products of protein digestion, such as amino acids and smaller peptides, will further stimulate acid secretion through stimulation of parietal cells and secretion of gastrin
   b. cause further protein digestion and acid secretion (positive feedback loop)
   c. once stomach pH falls below 2.5, gastrin is reduced and acid secretion is inhibited at pH of 1
3. Intestinal Phase: inhibition of gastric activity caused by small intestinal digestion through neural inhibition
   a. as chyme enters the duodenum, the distention and increase in osmolality will trigger a neural reflex to inhibit gastric activity
   b. presence of fat in the chyme will further inhibit gastric activity through secretion of an enterogastrone hormone (ex. somostatin and CCK)

Question 48

Describe the gastroileal, ileogastric and intestino-intestinal reflexes.

Answer 48

Gastroileal: increase gastric activity, increase ileum motility, thus increased movement of chyme through the ileocecal valve (from ileum into cecum)
Ileogastric: decrease in ileal distention, decrease in gsatric motility
Intestino-Intestinal Reflexes: increase distention in a segment of intestine, relaxation of the rest of the intestine

Question 49

Identify regulator of pancreatic juice and bile secretion.

Answer 49

Secretion of Pancreatic Juices:
-ACh (vagus nerve)
-CCK: secretion by duodenum due to stimulation of protein and fat in chyme; secretion of digestive enzymes from pancreas
-Secretin: secreted by duodenum due to low pH; secretion of bicarbonate from pancreas
Secretion of Bile:
-presence of a meal (sends signal to liver via enterohepatic circulation)
-Secretin: stimulates bile ducts to secrete bicarbonate, increasing volume of bile
-CCK: due to presence of fat stimulates contraction of gall bladder and delivery of more bile to duodenum
-presence of chyme; stimulates a neural reflex which in turn stimulates contraction of gall bladder

Question 50

Describe the role of cholecystokinin (CCK) on digestion and secretion.

Answer 50

CCK: stimulate secretion of pancreatic enzymes and trigger contraction of gall bladder for digestion of fat

Question 51

Describe the role of secretin on digestion and secretion.

Answer 51

-secretin stimulates water and bicarbonate release from the pancreas to help neutralize the acidity of chyme that is leaving the stomach
-will raise the pH in the duodenum to allow digestive enzymes to function
-secretin will further promote secretion of pancreatic enzymes along with CCK

Question 52

Identify hormones that regulate appetite.

Answer 52

Ghrelin: stimulates appetite
Peptide YY, CCK, Insulin, Leptin: inhibits appetite

Question 53

Discuss the digestion and absorption of carbohydrates including: amylase (ptyalin), maltase, sucrase, and lactase.

Answer 53

-digestion of carbs begins in the mouth with salivary amylase
-in small intestine; pancreatic amylase will hydrolyze polysaccharides into smaller chains of glucose (short oligosaccharides, maltrotose, maltose)
-enzymes in brushborder will hydrolyze disaccharides (sucrose, lactose, maltose) into monomers; can be absorbed across apical membrane of epithelial cells via secondary active transport (glucose/Na+ transporter)
-glucose is transported across basolateral membrane into interstitial fluid and capillary blood by facilitated diffusion via GLUT transporterss
Luminal Enzymatic Digestion of Carbohydrates:
Maltase: maltose, maltotriose & oligosaccharide -> glucose
Sucrase: sucrose -> glucose + fructose
Lactase: lactose -> glucose and galactose
-fibre is a carbohydrate; can’t be enzymatically digested and will enter large intestine undigested; undergo bacterial fermentation
-important for ruminants; hind gut fermenters require more bacteria because they have a diet high in fibre and rely heavily on microbial fermentation

Question 54

Discuss the digestion and absorption of proteins including: pepsin, trypsin, chemotrypsin, elastase, and carboxypeptidase.

Answer 54

-protein digestion begins in stomach; pepsin cleaves peptide bonds to form short-chain polypeptides
-majority of protein digestion takes place in the duodenum and jejunum where pancreatic enzymes will cleave internal peptide bonds
Endopeptidases: trypsin, chemotrypsin
Exopeptidase: group of enzymes that will cleave peptide bonds at end of polypeptide chain at carboxyl or amino end
Pepsin: in stomach; protein - shorter polypeptides
Trypsin, Chymotrypsin, Elastase, Carboxypeptidase: in small intestine (lumen); polypeptides - amino acids, dipeptides, tripeptides
-free amino acids can then freely cross the basolateral membrane into interstitial fluid and into blood capillaries

Question 55

Discuss the digestion and absorption of lipids including: lipase and phospholipase A.

Answer 55

Lipids are digested by pancreatic lipase, in the small intestine with the help of micelles (bile salts) to emulsify fat into smaller droplets, allowing access for enzymatic digestion by lipases.
-lipases will hydrolyze triglycerides into 3 fatty acids and 1 glycerol molecule
-phospholipases will hydrolyze phospholipids to produce 2 free fatty acids and 1 lecithin molecule
Small Intestine (Lumen):
Phospholipase A
-Triglyceride -> 3 free fatty acids + monoglycerides
-Phospholipid -> 2 free fatty acids + lecithin
-free fatty acids and glycerides are polar, they will associate with micelles (bile salts) to be transported to the epithelial surface
-will dissociate from the micelle and be absorbed across the apical cell surface through diffusion
-once inside enterocyte; free fatty acids and monoglycerides recombine and attach with protein to form chylomicrons
-Chylomicrons - secreted into central lymphatic lacteal via exocytosis transported through lymphatic circulatory system and enter venous system via thoracic duct

Question 56

Describe the role of bile, micelle, emulsification, lacteals, chylomicrons in absorption of fats.

Answer 56

Bile: contains bile salts that will help dissociate fat into chyme by emulsifying large droplet of fat into smaller ones
Micelle: helps transport fatty acids/monoglycerides to intestinal epithelium; bile salts surround lipid droplet
Emulsification: increases surface area for enzymatic digestion by lipases
Lacteals: absorbs chylomicrons into lymphatic circulatory system
Chylomicrons: transport of triglycerides through lymphatic system

Question 57

Discuss how fats are transported in the blood.

Answer 57

-once in the blood, chylomicrons dissociate
-free fatty acids will attach to albumin in blood plasma
-cholesterol travels to the liver where it will combine with apolipoproteins and triglycerides and secreted in the blood as VLDL (very-low-density lipoprotein) and LDL (low-density lipoprotein)