different modes of feeding and digestion

8/10/2019 different modes of Feeding and Digestion

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De Mesa, Czarina Anne E.

BS Biology 4-1 Environmental Physiology

FEEDING AND DIGESTION

Mechanisms with Particulate food

A. Pseudopodial (e.g Protozoans)

Pseudopods consist of fingerlike

projections of the cell membrane and

its contents (cytoplasm) that surround

and engulf food.

B. Ciliary (e.g., sponges, bivalve mollusks)

Cilia are minute hairlike projections of

cell membranes that, by concerted

beating in wave rhythm, set up water

currents or physically move food

particles.

C. Tentacular (e.g., certain sea

cucumbers).

Tentacles are slender, flexible organs on

the head. They may function in sensory

perception and in actually securing

food.

D. Mucoid (e.g., many snails, such as

Vermetus)

the food particles become attached to a

sticky mucous sheet secreted by special

cells.

E.

Muscular (e.g., certain coelenterates)

In the jellyfish Rhizostoma, pulsations

of the bell-shaped body draw water and

food in through perforations in the

arms, then expel the water after the

food is removed.



Functions of Alimentary Canal

Reception

• includes mouth and mouth cavity

-Posses glands that are primarily

lubricating

Conduction and storage

• This includes the esophagus and crop of

many species.

• Digestive glands may be present in this

region, or digestive enzymes may be

regurgitated from more distal regions.

Digestion and Internal Trituration.

• It is not uncommon to find associated

with the grinding mechanism a filtering

mechanism which maintains the food

particles

• In the region of the triturating

mechanism until they have been

reduced to a particular degree of

fineness.

Absorption

• This region usually overlaps the

preceding one, and in many animals,

such as the clams, starfishes, and

crustaceans, it is indistinguishable from

the region of storage and internal

trituration. In the majority of species,

including the sea urchins, sea

cucumbers, insects, annelids, and

vertebrates, the region of absorption is

more or less distinct.

Conduction and Feces Formation

• This region is very conspicuous in such

animals as the terrestrial insects and

vertebrates, in which an important

function is the absorption of water from

the fecal material, as in the insect

hindgut and the vertebrate colon. The

whole intestine of crustaceans and of

most molluscs comprises this region

Site of Digestion

Digestion of Proteins

Stomach: Digestion begins in the

stomach. The enzyme pepsin breaks

large protein chains (strings of amino

acids) into smaller chains called

proteoses, peptones, and polypeptides.

Pepsin relies on hydrochloric acid (HCL)

to activate it. As HCL is secreted, the

pH of the stomach drops. At a pH ofapprox. 2, the pepsin becomes fully

active.

Small Intestine:

Pancreas: Secretes enzymes

(trypsin, chymotrypsin and

carboxypolypeptidase) into small

intestine. These enzymes act on the

small chain proteins. Additional

enzymes are secreted by the small

intestines. The small chain proteins areconverted into amino acids.

Digestion of Carbohydrates

Mouth: Digestion begins in the saliva in

the mouth. The enzyme amylase,

contained within the saliva (produced

by the parotid gland), breaks down the



starch to smaller compounds called

dissacharides (maltose and isomaltose).

Stomach: The enzyme amylase

continues to act on the food for several

hours, lowers the pH below 4.0.

Small Intestine: Pancreatic amylase

(produced by the pancreas), along with

other enzymes produced by the small

intestine (maltase, isomaltase, lactase,

sucrase), convert the dissacharides into

monosaccharides (glucose, fructose and

galactose) which can easily be

absorbed. These simple sugars enter

circulation.

Liver: In the liver, the fructose and

galactose are converted to glucose.

Digestion of Fats

Small Intestine: Digestion of fat mainly

occurs in the small intestine.

Liver:produces bile salts, stores it in gall

bladder. These bile salts are secreted

into small intestine, where they

emulsify and break up fat into small fat

globules. These globules are still

triglycerides (no chemical change has

occurred yet, as bile is not an enzyme).

The purpose of the bile is to increase

the surface area of the fat.

Pancreas :secretes the enzyme lipase

into the small intestine. Lipase

transforms the triglycerides into fatty

acids and glycerol.

different modes of feeding and digestion

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