BIOM 3200 Term Test 1 - Digestion & Cardio

What are the three main functions of the digestive system

Breakdown of ingested food, absorption of nutrients into the blood, concentration and removal or waste products

The alimentary canal is a ____ tube

hollow

List the organs that make up the alimentary canal

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus

What are the accessory organs of the digestive system

Salivary glands, liver, gall bladder, pancreas

What are the functions of the salivary glands

• lubrication/binding

• solubilization of dry food

• oral hygiene - flushes away debris

• begins starch digestion (salivary amylases)

• alkaline buffering

  • evaporative cooling

Name the four types of teeth and their functions

• incisors - rip, cut

• canines - tear, pierce

• premolars - grind, shear

  • molars - grind

What is mastication

Chewing food - add salivary amylases

What is deglutition

Swallowing - requires 25 pairs of muscles in the mouth, pharynx, larynx, upper esophagus

Mouth, pharynx, upper esophagus

muscles innervated by somatic motor neurons

Middle and lower esophagus

muscles innervated by autonomic neurons

How does food move through the esophagus

oral —> pharyngeal —> esophageal

The process of wave-like muscular contraction that moves food is called

peristalsis

What are the three layers of muscle in the stomach

Circular, longitudinal, oblique

Describe how the muscles of the stomach contribute to digestion

They are arranged perpendicularly to provide complex motility

What are the gastric pits and gastric glands

Gastric pits are the openings of the gastric glands

gastric glands consist of several types of cells

each cell type produces a specific secretion

What are the three types of cells found in gastric glands and their secretions

• Mucous cells; secrete mucus

• Parietal cells; secrete HCl, intrinsic factor B12

  • Chief (zygomatic) cells; secrete pepsinogen

What is the role of mucous cells

Helps the stomach not digest itself - erosions of the mucosa can lead to peptic ulcers (i.e. the stomach digest itself) caused by Helicobacter pylori

What role does HCl play in the stomach

In the presence of HCl, the inactive enzyme pepsinogen is activated to form the pepsin form, which can digest proteins into smaller polypeptides

List the three regions of the small intestine

• duodenum

• jejunum

  • ileum

Which region of the small intestine receives secretions from the pancreas and liver

Duodenum

Compare the jejunum and ileum in terms of length and structure

Jejunum is 1m in length, has numerous folds and villi

Ileum is the last 2m, fewer folds/villi than jejunum

What are Peyer’s patches and where are they found

Aggregations of lymph nodes found in the ileum

What is the function of goblet cells

Secrete mucous

What is the role of Paneth cells

Found at the base of the crypts and secrete antibacterial molecules (lysozymes, antimicrobial peptides) to protect the intestine from inflammation

Where are the brush border enzymes located

Attached to the cell membrane of microvilli in the small intestine

How do ‘good’ bacteria protect the colon

They out compete pathogenic bacteria

What happens when pathogenic bacteria take over the colon

diarrhera

What is the role of the appendix in the digestive system

contains a reservoir of ‘good bacteria’ that can recolonize the colon following diarrhea and expulsion of the colon content

Intestinal microbiota are about ____ times more than # of human cells in the body

10X

List the accessory organs of digestion

• pancreas

• liver

  • gall bladder

describe the structure of the liver

• made up of hepatic cells lining large capillaries call sinusoids

  • sinusoids are also lined by endothelial cells and contain Kupffer cells (phagocytes)

What are the two sources of blood supply to the liver

1. portal vein - coming from intestines, major source of blood

2. hepatic artery - blood from heart

What are the two main functions of the liver

1. endocrine function - where enzyme and hormones do their thing and output gets sent into hepatic vein and goes back to heart so nutrients can get pumped through whole body

2. two exocrine regions - L/R hepatic ducts that come out which makes bile. the L/R hepatic ducts meet up with cystic duct from gall bladder to form common bile duct

How is bilirubin processes by the liver

A derivative of Heme is converted into bilirubin, carried in the blood on albumin proteins, taken up by the liver, mixed with glucoronic acid, and now is water soluble and can be secreted into bile, to intestine, converted by bacteria into urobilinogen, and removed in feces

What is the function of the gallbladder

• sac-like organ attached to the inferior surface of the liver

  • stores and concentrates bile from the liver

What are gallstones and how are they treated

mineral deposits that produce painful symptoms by obstructing the bile ducts

usually removed by surgery, sometimes oral ingestion of bile acids or fragmentation by high energy shock waves

What are the dual functions of the pancreas as both an endocrine and digestive organ

1. endocrine gland making hormones

2. digestive organ secreting digestive enzymes destined for small intestine. enzymes help digest cyme, carbs, proteins, lipids

What is the function of the pancreatic juice

Contains ~20 different digestive enzymes

What digestive enzymes are found in pancreatic juice

• amylase - digests starch

• trypsin - digests proteins

• lipase - digests trigylcerides

How is trypsin activated

Activated by the brush border enzymes; its a protease that can then activate other pancreatic enzymes

What are the major classes of carbohydrates

• polysaccharides - starches, complex carbohydrates

• disaccharides - sucrose, maltose, lactose

• monosaccharides - glucose, fructose, galactose

List the major enzymes involved in the digestion of carbohydrates

• lactase - converts lactose into galactose and glucose

• sucrase - converts sucrose into glucose and fructose

• maltase - converts maltose into 2 molecules of glucose

• alpha-dextrinase - converts small glucose polymers into multiple molecules of glucose

Where does the digestion of carbohydrates begin

Chewing - mixes food with salivary secretions containing ptyalin

What is the role of ptyalin

Hydrolyzes starch into maltose and other small glucose polymers

Where does most of carbohydrate digestion occur

Duodenum and jejunum

How are disaccharides digested and what are the products

Disaccharide sugars, lactose, sucrose and maltose are digested by brush border enzymes, lactase, sucrase, and maltase

What are the final products of carbohydrate digestion

All monosaccharides

Where are monosaccharides absorbed into the blood stream

They are internalized by the absorptive cell and diffuse out into caps of the intestinal villi

Where does blood leaving the villi of the small intestine drain

Into blood vessels that directly lead to the liver - the hepatic portal system

What is the first pass effect

As blood passes through the blood vessels of the liver, much of the nutrient load is removed

What happens to excess glucose in the body

Can be converted into glycogen and stored in the liver and muscle

What is the role of insulin

Insulin helps bring glucose into cells

What are the major classes of lipids

• triglycerides

• phospholipids

• sterols (such as cholesterol)

Where does the digestion of fats begin and how much fat digestion occurs there

a very small amount occurs in the stomach

accounts for <10%

What is the role of bile salts in fat digestion

They help lipid digestion by emulsifying lipids - they are broken down into smaller droplets; this has the affect of greatly enhancing access of the lipases to lipid molecules

What enzymes are responsible for digesting lipids

Lipases - only present in pancreatic juice so lipid digestion can only occur in the small intestine

How are triglycerides digested by pancreatic lipase

Pancreatic lipase spilts triglycerides to free fatty acids and monoglycerides

How are the products of lipid digestion absorbed

They diffuse into the absorptive cells which can re-synthesis triglycerides from monoglycerides and fatty acids

What are chylomicrons and what is their role

• they are secreted into central lacteals of the intestinal villi, passing via the lymphatic system until they eventually reach the blood through the thoracic duct

• in the blood, they add ApoE protein which helps it to bind to capillaries in the target muscles and adipose tissue

How are proteins digested and what are the end products

• protein digestion (by proteases) produces large polypeptides

• digestion of these large polypeptides (by peptidases) produces smaller amino acid chains (peptides)

• peptides are then digested (by peptidases) into amino acids

What is the role of pepsin in protein digestion

• the important proteninase in the stomach, only functions at a pH of 2-3, inhibited at pH>5

• one of the only enzymes capable of digesting collagen

What enzymes are present in pancreatic secretions that digest proteins

• trypsin

• chymotrypsin

• carboxypeptidase

• proelastase

Where does the final digestion of proteins occur and how

• occurs in small intestinal villi

• endopeptidases (like trypsin) cleave off internal bonds of amino acids

• exopeptidases cleave off the ends

How are amino acids transported into absorptive cells

Transported by transport proteins (carrier-mediated transport)

What happens to excess amino acids

Immediately metabolized by liver cells

the nitrogen (amine) unit of the AA is removed to make urea; the remaining part of the molecule is converted into lipid

How are calcium ions absorbed

active absorption into the blood

controlled stringently

• parathyroid hormone activates vitamin D - enhances calcium absorption

Why is iron absorption important

important for the formation of Hb

How are vitamins absorbed in the intestine

Through the passive process of diffusion in the jejunum and ileum

How are fat-soluble vitamins absorbed

Absorbed with dietary lipids (vitamins A, E, D, K)

What is the exception for the absorption of water soluble vitamins

vitamin B12 - this vitamin combines with intrinsic factors produced by the stomach which the intestine absorbs by endocytosis