? bite off chunks of food, or take in a whole organism, in one feeding

§ Humans are bulk feeders.
§ Tend to eat discontinuously – they have discrete

periods of eating and not eating 

? (suspension feeders) sift small food particles from the water

§ Baleen whales are filter feeders that eat tons of small, shrimplike animals called krill 

? include parasites that live in body fluid of a host, and external parasites, which tap into host’s vascular system

§ A vampire bat has fangs (pointed incisors) for piercing the skin of its host in order to get at its blood 

? live on, or in, the material they eat

§ Caterpillars live and feed on leaves 

1. Ingestion – act of taking in food during the process

of feeding

2. Digestion
§ Mechanical digestion can be accomplished by chewing

with mouthparts such as teeth

§ Chemical digestion requires enzymes secreted by the digestive tract or by glands (Usually in 2 steps)

3. Absorption – occurs when nutrients are taken into the body, often into the bloodstream

4. Elimination (defecation) – removal of waste products that pass through the anus

A ruminant’s stomach

? is a thick-walled organ that is continuous with esophagus and duodenum

§ Stores food, initiates digestion of protein, and controls movement of chyme into small intestine

§ Does not absorb nutrients
§ Wall of stomach contains three layers of

smooth muscle for mechanical digestion
§ Rugae, Gastric pits, Gastric Glands
§ Pepsin in gastric juice breaks down proteins

§ Food leaves stomach as a thick, soupy liquid called chyme 

Small intestine

§ Ducts bring in bile from liver and gallbladder and pancreatic juice from pancreas (Duodenum)

§ Bile emulsifies fat
§ Enzymes in pancreatic juice (basic pH) for chemical digestion

(Pancreatic Amylase, Trypsin, Lipase, nuclease)

§ Anatomic features increase the surface area of the small intestine

§ Fingerlike villi with extensions called microvilli
§ Villi also bear enzymes that finish chemical digestion

§ Nutrient molecules are absorbed into the vessels of a villus, which contains blood capillaries and a lymphatic capillary called a lacteal 

Large intestine – larger in diameter but shorter in length than the small intestine

§ Includes the cecum, the colon, the rectum, and anus § Absorbs water, salts, and some vitamins
§ Stores undigestible material until it is eliminated
§ No digestion takes place

§ Large population of bacteria=coliforms (Escherichia coli) that are normally nonpathogenic

§ Break down undigestible material
§ Produce Vitamin K for blood clotting 

The Pancreas

§ Both endocrine and an exocrine functions

§ Produces hormones insulin and glucagon

§ Produces pancreatic juice, with sodium bicarbonate (NaHCO3) and digestive enzymes 

The Liver

§ Largest gland in the body

§ Removes poisonous substances from the blood and detoxifies them

§ Maintains blood glucose levels
§ Produces bile, which is stored in the gallbladder 

Functions of Liver

Detoxification
Stores Vitamins
Manufactures Plasma Proteins, cholesterol Helps in the regulation of Blood Glucose Synthesizes Glucose from amino acids and lipids Synthesis of Urea
Synthesis of Bile

Disorders of Liver

Jaundice (Viral, hemolytic or obstructive) Viral Jaundice (Hepatitis A, B and C) Cirrhosis 

Carbohydrates are present in food in the form of sugars, starch, and fiber

§ Fiber includes various nondigestible plant carbohydrates

§ Not a nutrient for humans, but adds bulk to fecal material, which stimulates movement in the large intestine, preventing constipation 

Triglycerides (fats and oils) supply energy for cells, but fat is stored for the long term in the body

§ Good Fats= Unsaturated Fats; Bad Fats=Saturated Fats; Worst Fats=Trans Fats

§ Cholesterol – a lipid that can be synthesized by the body (not present in plant foods)

§ Cells use cholesterol to make various compounds, including bile and Vitamin D 

Dietary proteins are digested to amino acids, which cells use to synthesize hundreds of cellular proteins

§ Total amino acids =20; Body can synthesize 11 amino acids; The other 9 amino acids must be supplied through balanced diet.

§ Complete or high quality proteins incomplete or low quality proteins 

• Water is H2O.

• Water molecules can form Hydrogen bonds with

  adjacent water molecules (not exclusive to H2O)

• Hydrogen bond is weaker than ionic bond and covalent bond

• Hydrogen bonding accounts for most of the properties of water that make life possible

• Melting point 0C and Boiling point 100C because of hydrogen bonding (If not m.p=-100C and b.p=-91C)

• Water molecules exhibit Cohesion and Adhesion because of hydrogen bonding 

Hydrogen bonding accounts for most of the properties of water that make life possible

– Changes the freezing and boiling point of water

– Cohesion – water molecules stick together

– Adhesion – water molecules stick to other polar molecules 

As a result of cohesion and adhesion, water is an excellent transport medium within vessels in both plants and animals.

• The many hydrogen bonds that link water molecules help water absorb heat, without great change in temperature.

• 1g of water at 0C must lose 80c of heat to give 1g of Ice

• 1g of water at 100C must gain 540c of heat to become water vapor.(High heat of vaporization)

• One calorie is the amount of heat energy required to raise the temperature of 1g of water by 1C