Ingestion, Digestion, Absorption

Essential amino acids

Amino acids that are needed, but cannot be made by the body; they must be eatin in foods

vitamins and minerals

used to regulate normal body functioning.

Foregut vs. Hindgut

Foregut

• limited availability/absorption of dietary glucose

• direct availability of microbial protein and nutrients

• Rumination allows particle reduction -detoxification Hindgut

• availability/absorption of dietary glucose

• no direct availability/absorption of microbial protein and nutrients

• reliance on coprophagy and cecotrophy in some species

Hindgut

distal 1/3 of transverse colon to anal canal above pectinate line

mechanical digestion

Physical breakdown of large pieces of food into smaller pieces

chemical digestion

Process by which enzymes break down food into small molecules that the body can use

Ingestion

Intake of food

Digestion

Breakdown of food substances into simpler forms that can be absorbed and used

Absorption

The process by which nutrient molecules pass through the wall of the digestive system into the blood

expulsion

the process of driving or forcing out

mouth

where digestion begins

saliva

The fluid released when the mouth waters that plays an important role in both mechanical and chemical digestion

Amylase

Enzyme in saliva that breaks the chemical bonds in starches

Esophagus

A muscular tube that connects the mouth to the stomach.

Peristalsis

Involuntary waves of muscle contraction that keep food moving along in one direction through the digestive system.

stomach

large muscular sac that continues the mechanical and chemical digestion of food

Pepsin

An enzyme present in gastric juice that begins the hydrolysis of proteins

pepsinogen

The inactive form of pepsin that is first secreted by specialized (chief) cells located in gastric pits of the stomach.

HCL in digestion

Bactericide, activates pepsinogen by breaking it down into pepsin, stomach protected by mucous (no mucous-->ulcers form)

Lipases

enzymes that break down lipids

parietal cells

secrete HCl and intrinsic factor

pyloric sphincter

Controls passage of food from stomach to small intestine

small intestine

Digestive organ where most chemical digestion and absorption of food takes place

duodenum

first part of the small intestine

Pancreas

Regulates the level of sugar in the blood

CCK

stimulates gall bladder to secrete bile to emulsify fats in the small intestine

gall bladder

An organ that stores bile and releases it as needed into the small intestine

bile salts

compounds in bile that aid in emulsification

Secretin

A hormone secreted by the small intestine (duodenum) in response to low pH (e.g., from stomach acid). It promotes the release of bicarbonate from the pancreas to act as a buffer.

HCO3- and digestive enzymes

What are the two important constituents of pancreatic juices?

pancreatic duct

conducts pancreatic juice from the pancreas to the small intestine

Villi and microvilli in the small intestine _____.

increase the surface area to increase the efficiency of nutrient absorption

Na/glucose cotransporter

Na+ moves downhill into cell while glucose moves uphill Does not change Na/K gradient established by pump

glucose transporter protein

the red blood cell (RBC) glucose transporter

hepatic portal system

the veins that carry blood from the digestive organs to the liver

liver

produces bile

large intestine

Absorbs water and forms feces

colon

large intestine

rectum

A short tube at the end of the large intestine where waste material is compressed into a solid form before being eliminated

Cellulose

A substance (made of sugars) that is common in the cell walls of many organisms

Cellulase

enzyme that breaks down cellulose

hindgut fermenters

modified regions of the colon and caecum for bacterial digestion.

Forgut fermenters

• Bacteria break down cellulose before organism digests/absorbs food

• Cellulose handled BEFORE hitting digestion/absorption

• Bacteria can turn cellulose into something useful for organism

• RUMEN=CONTINUOUS FLOW REACTOR

• Low quality food

Short Chain Fatty Acids (SCFA)

<6 C; digested and transported quickly

Rumen

stomach chamber in cows and related animals in which symbiotic bacteria digest cellulose

cecum

a pouch connected to the junction of the small and large intestines.

cecotrope

waste that in re-ingested

Coprophagy

ingestion of feces