Digestive System Flashcards

Question

Anatomy of liver

Answer 1

Four (4) lobes-right, left, quadrate, and caudate • Falciform ligament separates left and right lobes • Sheet of mesentery that suspends the liver from the diaphragm • Gallbladder depression on inferior surface • Inferior Vena Cava sulcus on posterior aspect

Answer 2

Hepatic lobules - central vein helps with Venus blood drainage - hepatocytes - hepatic sinusoids are blood filled channels. Allows transfer of molecules and nutrients. is hepatocytes from blood cells • Absorb glucose, amino acids, iron, vitamins & nutrients required for metabolism • Degrade hormones, toxins, bile pigments and drugs Hepatic triad: •Branch of hepatic artery supply oxygenated blood to liver • Branch of hepatic vein carry nutrient rich blood from the same intestine and facilitate drainage of deoxygenated blood and wats substance from liver • Bile duct helps transport bile

Answer 3

Liver receives blood from 2 sources: ~70% hepatic portal vein & 30% hepatic arteries • Hepatic portal vein = blood from stomach, intestines, pancreas, spleen • All nutrients except lipids • Hepatic arteries = arterial blood from aorta at the celiac trunk to hepatic artery proper Meet and drain into sinusoids; mixing venous and arterial

Answer 4

Stores and concentration of bile with simple columnar epithelium tissue inside it, which helps with absorption and secretion related to that bio management.

Answer 5

It contains a mix of minerals, cholesterol, neural neutral fats, phospholipids, bile pigments, and bile acids. Green fluid containing minerals, cholesterol, neutral fats, phospholipids, bile pigments and bile acids. Bilirubin - principle pigment comprised of decomposed hemoglobin Reaches small intestine turns to Urobilinogen - • Urobilin responsible for yellowish colour of urine - Remiaining urobilinogen responsible for brown colour of feces Bile acids - steroids synthesised from cholesterol -With lecithin (phospholipid and micelles - aid in fat digestion and absorption All other components = wastes • In excess, can lead to gallstones Bile is collected in the gallbladder with the bile duct reaches full capacity Reabsorbs water and electrolytes • Increase concentration of bile 5-20x Liver secretes about 500 to 1,000 mL of bile daily 80% of bile acids are reabsorbed in the ileum and returned to the liver 20% of the bile acids are excreted in the feces

Answer 6

while is green. And it's a digestive fluid that's made in the liver stored in the gallbladder and helps digest.It helps with digestion and helps with absorption of fats.

Answer 7

Spongy retroperitoneal gland posterior to the stomach Measure 12 to 15 cm long, and 2.5 cm thick Components • Head (encircled by duodenum) • Body (mid-portion) • Tail on the left Both an endocrine and exocrine gland • Endocrine portion- -pancreatic islets that secrete insulin and glucagon. • Exocrine portion- 99% of pancreas that secretes 1,200 to 1,500 mL of pancreatic juice per day.

Answer 8

• Runs lengthwise through the middle of the gland

Answer 9

• Smaller duct that branches from the main pancreatic duct • Opens independently into the duodenum • Bypasses the sphincter and allows pancreatic juice to be released into duodenum even when bile is not

Answer 10

Alkaline mixture of water, enzymes, zymogens, sodium bicarbonate, and other electrolytes Important ones . Pancreatic amylase - splits glycogen into disaccharides • Pancreatic lipase - breaks down triglycerides • Trypsinogen, chymotrypsinogen, and carboxypeptidase (digest proteins) • Nucleases - digest nucleic acids • Bicarbonate ions - make pancreatic juice alkaline

Answer 11

Three (3) stimuli are responsible for the release of pancreatic juice and bile 1. Acetylcholine (Ach) • From vagus and enteric nerves •Secrete enzymes during the cephalic phase 2. Cholecystokinin (CCK) •Secreted by mucosa of duodenum and small intestine •In response to fats in small intestine •Contraction of gallbladder and relaxation of hepatopancreatic sphincter > discharges bile into duodenum 3. Secretin •Produced by small intestine in response to acidity of chyme from stomach •Stimulates liver and pancreas to secrete sodium bicarbonate solution (buffers the hydrochloric acid arriving from the stomach)

Answer 12

Nearly all chemical digestion and nutrient absorption occurs in the small intestine "Small" intestine refers to the diameter-not length (2.5 cm) The longest part of the digestive tract

Answer 13

Coiled mass filling most of the abdominal cavity inferior to the stomach and the liver Divided into three regions 1. Duodenum: first 25 cm (10 in.) • Begins at the pyloric valve • Major and minor duodenal papilla distal to pyloric valve • Receives major and minor pancreatic ducts respectively • Arches around the head of the pancreas • Ends at a sharp bend called the duodenojejunal flexure Function: • Stomach acid neutralised, in the duodenum, fats emulsified by bile acids, pepsin inactivated by pH & pancreatic enzymes take over chemical digestion. 2. Jejunum: first 40% of small intestine beyond duodenum • Roughly 1.0 to 1.7 m in a living person • Large, tall, closely spaced circular folds • Relatively thick and muscular wall • Especially rich blood supply which gives it a red color • Most digestion and nutrient absorption occurs here 3. Ileum: forms the last 60% of the postduodenal small intestine • About 1.6 to 2.7 m • Thinner, less muscular, less vascular, and paler pink color • Ileocecal valve (sphincter) control’s movement from the ilium to large intestine

Answer 14

Tissue layers have modifications for nutrient digestion and absorption Lumen lined with simple columnar epithelium Muscularis externa is notable for a thick inner circular layer and a thinner outer longitudinal Large internal surface area for effective digestion and absorption: by great length and three types of internal folds or projections Circular folds increase surface area by a factor of 2 to 3 Villi increase surface area by a factor of 10 Microvilli Increase the surface area by a factor of 20

Answer 15

Intestinal crypts secrete 1 to 2 L of intestinal juice per day • In response to acid, hypertonic chyme, an distension of the intestines • pH of 7.4 to 7.8 • Contains water, mucus, but relatively little enzyme • Most enzymes that function in the small intestine are found in the brush border

Answer 16

Contractions of the small intestine serve three (3) functions: To mix chyme with intestinal juice, bile and pancreatic juice allowing these fluids to neutralize acid and digest nutrients more effectively. Churn chyme and bring it into contact with the mucosa for digestion and absorption To move residue toward the large intestine

Answer 17

Segmentation • Movement in which ringlike constrictions appear at several places alc the intestine • Most common site is the small intestine •Allows the kneading/churning which promotes mixing of food, digesti secretions and enhances contact digestion. Pacemaker cells of the muscularis externa set the rhythm segmentation •8-9 times per minute in the ileum • 12 times per minute in the duodenum

Answer 18

Intensity of contractions is influenced by nervous and hormonal factors • When most nutrients have been absorbed, segmentation declines and peristalsis begins • A peristaltic wave begins in the duodenum and travels 10-70cm, then is followed by another wave. • The overlapping waves of contraction are called migrating motor complex •Chyme is milked towards the colon over ~2 hours •Refilling of the stomach at the next meal supresses peristalsis and activates segmentation •Ileocecal valve remains closed until food in stomach triggers the release of gastrin •Pressure pinches the valve shut

Answer 19

The Gl tract is a long, muscular tube that extends from the mouth to the anus and is responsible for the digestion and absorption of food. It can be divided into several distinct regions: 1. Oral Cavity (Mouth): 2. Pharynx: 3. Oesophagus: 4. Stomach: 5. Small Intestine: 6. Large Intestine (Colon): 7. Rectum: 8. Anus:

Answer 20

Digest Absorb Transport the nutrients

Answer 21

1. Oral Cavity (Mouth): - The process of digestion begins in the mouth. - Food is broken down mechanically by chewing, and enzymes in saliva start breaking down carbohydrates. Function of the Oral cavity 1. Enzyme Site: While the mauth is not a primary site for enzyme secretion, it does contain enzymes, such as salivary amulase. 2. Enzyme Name: Salivary amylase (also known as plyalin) 3. Role: Salivary amylase is responsible for initiating the digestion af carbohydrates (starches) in the mouth. it breaks down complex carbohydrates into simpler sugars, primarily maltose. This initial breakdown of carbohydrates is a crucial step in digestion.

Answer 22

First enzyme that helps break down carbohydrates

Answer 23

The substrate of food. When food goes in mouth and turns to mush it’s called bolus

Answer 24

1.Salivary Amylase (Ptyalin): 1. Source: Salivary amylase is secreted by the salivary glands, primarily the parotid glands, submandibular glands, and sublingual glands. 2. Role: Salivary amylase begins the digestion of complex carbohydrates, such as starches and glycogen, into simpler sugars. It catalyses the hydrolysis of starch molecules into maltose (a disaccharide composed of two glucose molecules) and other smaller sugar molecules. This process is the initial step in carbohydrate digestion and takes place in the mouth when you start chewing and mixing food saliva. 3. Optimal pH: Salivary amylase works best in a slightly alkaline or neutral pH. Apart from salivary amylase, the saliva in the oral cavity also contains other components like mucin, lysozyme, and immunoglobulins that help with lubrication, protection against pathogens, and maintaining oral health.

Answer 25

3. Oesophagus: - The esophagus is a muscular tube carrying food from the pharynx to the stomach through peristalsis. - There are sphincters at both ends of the esophagus to prevent backflow of stomach contents.

Answer 26

4. Stomach: - The stomach is a muscular organ that stores, mixes, and partially digests food. - It secretes gastric juices, including hydrochloric acid and enzymes, to break dow proteins.

Answer 27

Role of the Stomach: - Enzymes: a. Pepsin: Pepsin is the most significant enzyme produced 1 the stomach. It is secreted in an inactive form known as epsinogen by the chief cells of the gastric glands. When it omes into contact with hydrochloric acid (HCI), also roduced in the stomach, pepsinogen is converted into its ctive form, pepsin. Pepsin is responsible for breaking down roteins into smaller peptide fragments. b. Gastric Lipase: This enzyme is secreted by the stomach's chief cells. It plays a minor role in digesting fats, primarily breaking down dietary triglycerides into fatty acids and monoglycerides. - Function: The stomach's primary function is to: a. Mechanical Digestion:. b. Chemical Digestion c. Storage

Answer 28

5. Small Intestine: - The small intestine is where most digestion and nutrient absorption occur. - It consists of three sections: the a) duodenum, b) jejunum, and c) ileum. - Enzymes from the pancreas and bile from the liver help digest food, and nutrients are absorbed into the bloodstream through the intestinal walls.

Answer 29

Enzymes of the Small Intestines? Digestive Enzymes: - Pancreatic Enzymes: The pancreas secretes several digestive enzymes into the small intestine to break do macronutrients. - Pancreatic Amylase: This enzyme breaks down carbohydrates (starches) into simpler sugars like matterea glucose. - Trypsin and Chymotrypsin: These enzymes break down proteins into smaller peptides and amino acids, - Pancreatic Lipase: It digests fats (triglycerides) into fatty acids and monoglycerides, making them more absorbable. - Intestinal Enzymes: The small intestine's lining also produces enzymes. Intestinal Lipase: This enzyme continues the digestion of fats, particularly in the final stages of fat absorption. - Sucrase, Lactase, and Maltase: These enzymes break down disaccharides (sucrose, lactose, and maltose) into their constituent monosaccharides (glucose, fructose, and galactose), facilitating carbohydrat absorption.

Answer 30

Bile Function: - Bile is produced by the liver and stored in the gallbladder before being released into the small intestine. While bile is not an enzyme, it plays a crucial role in digestion. - Bile emulsifies fats, breaking them into smaller droplets. This emulsification process increases the surface area of fat particles, making it easier for lipases (enzymes) to digest and absorb dietary fats.

Answer 31

Large Intestine (Colon): - The large intestine absorbs water and electrolytes, forms faces from undigested food, and houses beneficial gut bacteria. - Fermentation - It comprises the cecum, colon, rectum, and anal canal.

Answer 32

Water absorption

Answer 33

7. Rectum: - The rectum is the last part of the large intestine before the anus. - It stores faces until they are ready to be eliminated.

Answer 34

8. Anus: - The anus is the external opening through which feces are expelled from the body.

Answer 35

Function: food goes though chemicals break down. Includes teeth, tongue and glands Enzymes: salivary amylase Process: mastication and carbohydrate breakdown

Answer 36

Function: mix, stage two digestion and absorption Enzymes: pepsin, HCL, lipase Process:

Answer 37

Function: Absorption and digestion Enzymes: pancreas, bile and sucrease Process:

Answer 38

Function: water absorb , absorb - feaces, fermentation Enzymes: Process:

Answer 39

Function: expell faeces Enzymes: Process::

Answer 40

Absorbs water and salts and eliminates feces by defecation

Answer 41

• Muscle tone of tenia coli contracts the colon lengthwise and causes its wall to form haustra • Haustra are absent in the rectum and anal canal

Answer 42

Anus is regulated by two sphincters: • Internal and external sphincters

Answer 43

Mucosa-simple columnar epithelium through entire large intestine Anal canal has nonkeratinized stratified squamous epithelium in its lower half • Provides abrasion resistance No circular folds or villi to increase surface area in large intestine Have a greater density of mucus-secreting goblet cells Lamina propria and submucosal layers have large amount of lymphatic tissue

Answer 44

Bacterial flora populate large intestine About 800 species of bacteria vary depending on many factors diet, age Play a digestive role Digest cellulose and other undigested carbohydrates Body absorbs resulting sugars Help in synthesis of vitamins B and K

Answer 45

Large intestine takes about 36 to 48 hr to reduce the residue of a meal to feces • Reabsorbs water and electrolytes Feces consist of: • 75% water; and • 25% solids • 30% is bacteria, • 30% undigested fiber • 10% to 20% fat • Small amount of mucus, and sloughed epithelial cells Haustral contractions occur every 30 minutes • This kind of colonic motility is a form of segmentation • Distension of a haustrum stimulates it to contract Mass movements occur 1-3x a day • Triggered by gastrocolic and duodenocolic reflexes • Filling of the stomach and duodenum stimulates motility of the colon • Moves residue for several centimeters with each contraction

Answer 46

Stretching of the rectum stimulates defecation It invokes tow involuntary reflexes 1. Intrinsic defecation reflex • Operates within the myenteric nerve plexus • Stretch signals travel through the plexus to the descending and sigmoid colon and the rectum • A peristaltic waves drives the faces out 2. Parasympathic defecation reflex • A spinal reflex: stretch signals are detected by th spinal cord, signals the pelvic nerves to intensify peristalsis (4) Impulses from the brain prevent untimely defecation by keeping the external anal sphincter contracted. Defecation occurs only if this sphincter also relaxes.

Answer 47

Involves the digestive enzymes breaking the bonds of the food macromolecules Macromolecules or macronutrients from our diet include:Carbohydrates Fats or lipids Protein

Answer 48

Starch - the most digestible carbohydrate • First digested to: • 1. Oligosaccharides that are up to eight glucose residues long • 2. Then into the disaccharide maltose • 3. Finally to glucose which is absorbed by the small intestine Process begins in the mouth • Salivary amylase hydrolyzes starch into oligosaccharides • Amylase works best at pH of 6.8 to 7.0 of oral cavity • Amylase quickly denatured on contact with stomach acid and digested by pepsin After the mouth • In the small intestine, pancreatic amylase converts starch - oligosaccharides and maltose within 10 min. • Chyme contact brush border enzymes: • Dextrinase, glucoamylase: oligosaccharides • Maltase: maltose - Sucrase: sucrose -› glucose + fructose - Lactase: lactose -› glucose + galactose

Answer 49

80% of absorbed sugar is glucose - Taken up by sodium-glucose transport (SGLT) proteins - Glucose transported out of absorptive cell into ECF by facilitated diffusion - Sugar entering CF increases its osmolarity - Draws water osmotically from lumen of intestine, through now leaky tight junctions between epithelial cells - Water carries more glucose and other nutrients by solvent drag - SGLT absorbs galactose, fructose is absorbed by facilitated diffusion - Glucose, galactose, and any remaining fructose are transported out of the base of the cell by facilitated diffusion - Absorbed by blood capillaries in the villus - Hepatic portal system delivers them to the liver

Answer 50

AAs absorbed by the small intestine come from 3 sources Dietary proteins Digestive enzymes digested by each other Sloughed epithelial cells digested by enzymes Endogenous As from last two sources - 30 g/day Exogenous AAs from our diet - 44 to 60 g/day Proteases (peptidases)-enzymes that digest proteins Begin in the stomach in optimum pH of 1.5 to 3.5 Pepsin hydrolyzes any peptide bond between tyrosine and phenylalanine •Pepsin digests PRO into shorter peptides and some free AAs

Answer 51

Pancreatic enzymes trypsin and chymotrypsin take over the process Oligopeptides taken apart one amino acid at a time by three more enzymes

Answer 52

Carboxypeptidase of the brush border continues to remove amino acids from the carboxyl (-COOH) end. Aminopeptidase of the brush border removes one amino acid at a time from the amino (-NH) end Dipeptidase splits dipeptides ( 09 into separate amino acids (9).

Answer 53

Hydrophobic quality of lipids makes their digestion and absorption more complicated than carbohydrates and proteins. Lipase enzymes digesting fat Lingual lipase secreted by the intrinsic salivary glands of the tongue • Active in mouth, but more active in stomach along with gastric lipase • 10% to 15% of lipids digested before reaching duodenum Fat enters duodenum as large globules exposed to lipase only at their surface Globules broken up into smaller droplets by lecithin and bile acids (components of bile)

Answer 54

Agitation by segmentation breaks up the fats into droplets The coating of lecithin and bile acids keeps it broken up, exposing far more of its surface to enzymatic action Lipase acts on triglycerides by removing the first and third fatty acids from glycerol backbone • Two free fatty acids (FFAs) and a monoglyceride

Answer 55

Absorption of these products and other lipids depends on minute droplets in the bile known as micelles • Made in liver and consists of 20-40 bile acid molecules with their own hydrophilic side group Micelles pass down bile duct into duodenum • Absorb fat-soluble vitamins, cholesterol and FFAs • They transport lipids to the surface of the intestinal absorptive cells

Answer 56

Not an digestive enzyme

Answer 57

Emulsification Fat globule is broken up and coated by lecithin and bile acids. Fat hydrolysis Emulsification droplets are acted upon by pancreatic lipase, which hydrolyzes the first and third fatty acids from triglycerides, usually leaving the middle fatty acid. Lipid uptake by micelles Micelles in the bile pass to the small intestine and pick up several types of dietary and semidigested lipids. Chylomicron formation Intestinal cells absorb lipids from micelles, resynthesize triglycerides, and package triglycerides, cholesterol, and phospholipids into protein-coated chylomicrons Chylomicron exocytosis and lymphatic uptake Golgi complex packages chylomicrons into secretory vesicles; chylomicrons are released from basal cell membrane by exocytosis and enter the lacteal (lymphatic capillary) of the villus.

Answer 58

Nucleic acids (DNA & RNA) present in smaller amounts Ribonuclease and deoxyribonuclease, hydrolyse these to nucleotides Brush border enzymes decompose nucleotides = phosphate ions, nitrogenous bases, and simple sugars (ribose from RNA and deoxyribose from DNA) Transported across the intestinal epithelium by membrane carriers & enter capillary blood of villus

Answer 59

Absorption of water and electrolytes

Answer 60

B. Ileocecal valve

Answer 61

A. Through sodium-glucose transport proteins (SGLT)

Answer 62

D. It maintains the sodium gradient across the membrane

Answer 63

B. They facilitate the movement of amino acids into epithelial cells

Answer 64

- Swallowing (oropharynx) • Peristalsis (esophagus, stomach small intestine. large intestine

Answer 65

* Chewing (mouth) • Churning (stomach) • Segmentation (small intestine)

Answer 66

• Nutrients and water to blood vessels and lymph vessels (small intestine) • Water to blood vessels (large intestine)

Answer 67

Mechanical Digestion • Mastication (Chewing) • Breaks down food • Increases surface area for chemical digestion Bolus Formation • Saliva • Mixes with and lubricates food particles • Tongue • Assists in mixing • Shapes the bolys Churning • Vigorous mixing and grinding initiated by the presence of food in the stomach • Facilitated by contractions of the Muscularis Externa • Bolus transformed into semi-liquid mass called chyme Purpose • Increases surface area for chemical digestion • Ensures thorough mixing with gastric juices containing enzymes and hydrochloric acid

Answer 68

Muscularis externa: Longitudinal layer Circular laver Oblique layer

Answer 69

Proteins = Large chains of amino acids (AAs) Amino Acids (AAs) •Types (20 in total) Essential (9): Obtained through diet Non-essential: Synthesized in the body Protein Sources •Complete (contain all 9 essential AAs) • Examples: meat, fish, poultry, cheese, eggs •Incomplete (lack one or more essential AAs) • Examples: green vegetables, grains, legumes

Answer 70

Mouth • Limited enzyme activity on proteins in the mouth • Primarily initiated in the stomach Stomach • Highly acidic (pH 1.5 to 3.5), optimal for protease activity •Pepsin (most important protein digesting enzyme) - Produced as pepsinogen, an inactive precursor, by chief cells in the stomach lining -Breaks proteins down into smaller peptides

Answer 71

Trypsin (Pancreatic Juice) Polypeptides -› smaller peptides Chymotrypsin (Pancreatic Juice) Further reduces peptides to smaller fragments Carboxypeptidase (Pancreatic Juice) Cleaves amino acids from the carboxyl end of peptides Aminopeptidase (Brush border) Cleaves amino acids from the from the N-terminus (amino end) Dipeptidase (Brush border) Dipeptides -› Amino acids

Answer 72

Not the primary site for protein digestion Some proteolysis through microbial enzymes Some AA synthesized by microbes

Answer 73

Protein digestion begins in the stomach by hydrochloric acid and the enzyme pepsin . Protein-digesting enzymes are secreted from the pancreas into the small intestine The small intestine is the major site of protein digestion; final digestion occurs here A small amount of dietary protein is lost in the feces Protein-digesting enzymes are also secreted from the brush border The liver regulates distribution of amino acids to the rest of the body

Answer 74

Amino acids

Answer 75

Dipentidase

Answer 76

Final breakdown of peptides into amino acids

Answer 77

Carboxypeptidase of the brush border continues to remove amino acids from the carboxyl (-COOH) end. Aminopeptidase of the brush border removes one amino acid at a time from the amino (-NH) end. Dipeptidase splits dipeptides into separate amino acids.

Answer 78

Into the hepatic portal vein

Answer 79

Triglycerides (95%) Fats (solid) & Oils (liquid) - Saturated (single bonds) - Unsaturated (at least one double bond) Chain Length •Short: soft at room temp • Long: hard at room temp Other 5% • Cholesterol • Phospholipids

Answer 80

Mouth • Lingual Lipase • Breaks down triglycerides into diglycerides and free fatty acids • Optimal pH: 6.7-7.0 • Incomplete due to short time in the mouth Stomach • Highly acidic (pH 1.5 to 3.5) due to hydrochloric acid (HCI) • Inactivates lingual lipase • Gastric lipase • Secreted from chief cells in the stomach • Triglycerides broken into diglycerides and fatty acids