Digestive System Part 2

Question 1

What has achieved the highest degree of specialization in fermenting plant material?

Answer 1

Ruminants; the ruminant (digastric stomach) is highly populated with anaerobic microbes that are able to break down cellulose into end products of fermentation.

Question 2

What is involved in the stomach of true ruminants?

Answer 2

Cattle, sheep, goats, deer, giraffes and antelopes. Their stomach is divided into four compartments.

Question 3

What are Pseudoruminants?

Answer 3

Llamas and camels. They are ruminants with a three-compartment stomach.

Question 4

What is the forestomach of a digastric animal?

Answer 4

Involved in storage and passage of indigested food, it contains the rumen, reticulum, and omasum.

Question 5

What is the Rumen?

Answer 5

Part of the digastric stomach; it’s involved in the anaerobic fermentation of plant material, the absorption of nutrients and simple molecules. It’s divided into internal compartments by pillars and has finger-like papillae that increase the surface area.

Question 6

What is the Reticulum?

Answer 6

Part of the digastric stomach; deals with the anaerobic fermentation of plant material and absorption of nutrients and simple molecules.

Question 7

What is the Osmasum?

Answer 7

Part of the digastric stomach; it provides a channel for passage of ingesta from the reticulum into the abomasum. It absorbs water and nutrients.

Question 8

What is the Abomasum?

Answer 8

Part of the digastric stomach; it resembles the stomach of monogastric vertebrates. It’s the acid-secreting region of the stomach, digests proteins and lyses rumen microbes.

Question 9

What is involved in organisms with no stomach?

Answer 9

These include some invertebrates (insects). When they have no stomach, they have outpouchings with enzyme-secreting cells plus phagocytic cells. Digestion and absorption are completed here, and the remainder of alimentary system is for water and electrolytes.

Question 10

What are Gastrointestinal Secretions?

Answer 10

The GI Tract is the largest endocrine and exocrine gland of the body.
Endocrine glands secrete hormones to the circulatory system.
Exocrine glands secrete digestive enzymes, water, mucus, and electrolytes into the lumen of the GI tract.

Question 11

What is important about Mammalian Salivary Glands?

Answer 11

They are an example of an exocrine gland. The acinar portion, the bulb, has the mucin, amylase, water, and electrolytes.
The duct portion is where further modification takes place.

Question 12

What is Saliva?

Answer 12

Digestive secretion (about 1L+/day) that has enzymes that breaks down sugars into monomers.

Question 13

What are Gastric Juices?

Answer 13

Digestive secretion from the stomach (1-3L/day) that are very acidic and can break down proteins. Pepsinogen, HCl, rennin, intrinsic factor.

Question 14

What are Pancreatic Juices?

Answer 14

Digestive secretions from the pancreas (1L/day) that are very basic and break down proteins, carbohydrates, and lipids.

Question 15

What is Bile?

Answer 15

Liver->Gallbladder secretion (1L/day) that breaks down cholesterol, fats.

Question 16

What is Succus Entericus?

Answer 16

Duodenum secretion (1L/day) that breaks down sugars.

Question 17

What controls secretion?

Answer 17

1. Presence of food in the same or a previous compartment
2. Chemoreceptors
3. Autonomic Nervous System
4. Endocrine cells release hormone into blood

Question 18

What controls secretion in the vertebrate stomach?

Answer 18

1. Cephalic phase - anticipation of food
2. Gastric phase - triggered by presence of food inside stomach (G cells detect food in the stomach, they release Gastrin - Chyme moves into the intestine. Gastrin is secreted in response to peptide, extension in stomach, and ANS stimulation. Gastrin stimulates HCl and pepsinogen secretion)
3. Intestinal phase - Gastic Inhibitory Peptide in response to fatty acids, this inhibits pepsinogen and HCL secretion, secretin stimulates pancreas and inhibits stomach.

Question 19

What are the Major Gastric Secretions?

Answer 19

Intrinsic factor and pepsinogen.

Question 20

What is absorption?

Answer 20

Occurs mostly in the intestine, it’s the breakdown of the products of digestion (only small particles) which is then transferred to the blood (or lymph - fat), and then distributed to the appropriate tissues.

Question 21

How can nutrients be absorbed in the intestine?

Answer 21

Through simple diffusion, facilitated diffusion (via carrier - glucose), active uptake (need energy), endocytosis (oligopeptides), and chylomicrons for lipids.

Question 22

How is sugar transported for absorption?

Answer 22

Through a Sodium gradient. Glucose and sodium use a co-transporter to put the glucose into the cell, where it diffuses into the blood.
SGLT1 = Na/glucose cotransporter.
GLUT5 = fructose facilitated transport.
GLUT2 = facilitated transport for sugars.

Question 23

How is Lipid Absorbed?

Answer 23

Bile salts (amphipathic molecules) are used as a detergent to emulsify the fat into micelles (hydrophobic). 
The monoglycerides, fatty acids, and glycerol then enter the cells by diffusion, and go to the Endoplasmic Reticulum for resynthesis. Chylomicrons (small droplets) from the golgi complex are made from this resynthesis, and they exit the cell by exocytosis and enter the lymph, and later the blood.

Question 24

What are Proteins and Amino Acids?

Answer 24

Amino acids can be used as energy sources, and are the building blocks of proteins.
Essential amino acids are those that can not be synthesized; species differences - some species produce different essential amino acids.

Question 25

What are Carbohydrates?

Answer 25

Sugars, starches, cellulose, glycogen. Used as sources for energy, and metabolized as glucose; stored as glycogen. Can be converted to amino acids and fats, proteins can be converted to carbohydrates by most animals.

Question 26

What are Lipids?

Answer 26

Used for energy, very suitable for storage (less water bound, higher density). Used in times of caloric deficit (hibernation), important as constituents of membranes.

Question 27

What are Nucleic Acids?

Answer 27

Essential for DNA and RNA; no need for uptake, the body synthesizes them.

Question 28

What are Electrolytes?

Answer 28

They have to be take up, some only in trace amounts. They are metals for enzymes, cofactors. Involved in redox reactions, used for oxygen transport. Can be found in shells and bones.

Question 29

What are Vitamins?

Answer 29

Diverse and chemically unrelated group of organic substances that are only required in small quantities. They are primarily cofactors for enzymes.