BIOL 1720 Lecture 2 Animal Nutrition and the Digestive System

Filter Feeder

An organism that feeds by straining suspended matter and food particles from water, typically using specialized structures such as gills or a filtering apparatus.

Fluid Feeder

An organism that feeds by sucking or absorbing fluids from their hosts or surroundings, usually utilizing specialized mouthparts.

Bulk Feeder

An organism that consumes large pieces of food, often using specialized adaptations like jaws or teeth to capture and digest prey.

Substrate Feeder

An organism that feeds on the substrate or surface on which it lives, often consuming organic material as it burrows or moves through it.

Herbivore

An organism that primarily feeds on plants, including leaves, stems, and roots, often having specialized digestive systems to break down cellulose.

Carnivore

An organism that primarily feeds on other animals, which can be classified as obligate carnivores that exclusively eat meat or facultative carnivores that can also consume non-animal sources.

omnivore

An organism that consumes both plants and animals, exhibiting dietary flexibility that allows for a varied intake of nutrients.

Herbivore Dentition

refers to the specialized teeth in herbivores adapted for grinding and processing plant material, often characterized by flat molars for chewing.

• Incisors for clipping

• Premolars and molars for grinding

Carnivore Dentition

Enlarged canines (gripping) and pointed

incisors and molars for shearing off pieces

small enough to swallow

Omnivore Dentition

Variety of specializations

Accommodate both vegetation and meat

(2 incisors, 1 canine, 2 premolar, 3 molars)

Incomplete Digestive System

single opening = Gastrovascular cavity

• Ex: Planarian / jellyfish

• Food enters through mouth and muscular pharynx (sucking)

• Wastes exit through mouth and muscular pharynx

• Lacks specialized parts

Complete Digestive System

two openings = Alimentary canal (long tube of organs makes a pathway for food to travel through the body)

• Ex: Earthworm

• Food enters through mouth

• Wastes exit through anus

Vertebrate Digestive Systems / Tracts Monogastric

Organisms with a single-chambered stomach, such as humans and pigs, that process food in a straightforward manner.

Rabbit Gut

longer in relation to body size for increase time for digestion and absorption

Cecotropes

rabbit fecal pellets re-ingested for maximum absorption

Avian Digestive

Systems / Tracts:

Crop

Food Storage

Avian Digestive

Systems: Proventiculus

Digestive juices and enzymes

Gizzard

Grinding (stones / grit)

cloaca

Common sewer – feces and

reproductive products

Ruminant Digestive Systems

Four Stomachs – Food needs a lot of processing

Ruminant Digestive Systems: Rumen and Reticulum

Contains prokaryotes (bacteria) and protist to Digest cellulose forming cud

Ruminant Digestive Systems: Omasum

Cud is regurgitated, chewed and swallowed into the omasum

Ruminant Digestive Systems: Abomasum

Enzymes produced by ruminant digest cud – “true stomach”

Where/Who makes methane?

bacteria in ruminant stomaches; released via passing gas

Digestion is

extracellular

Digestive enzymes are secreted by

Wall of the digestive tract, or nearby glands

Salivary glands

secrete saliva; containes digestive enzyme for carbohydrates

Liver function

major metabolic organ:

processes and stores nutrients;

produces bile for emulsification of fats

Gallbladder

stores bile from lover; sends to small intestine

pancreas

produces pancreatic juice: contains digestive

enzymes, and sends it to the small intestine;

produces insulin and secretes it into the

blood after eating

mouth

teeth chew food; tongue tastes and

pushes food for chewing and swallowing

pharynx

passageway where food is swallowed

esophagus

passageway where peristalsis pushes

food to stomach

Stomach

secretes acid and digestive enzyme for protein; churns, mixing food with secretions, and sends chyme to small intestine

small intestine

mixes chyme with digestive enzymes for final breakdown; absorbs nutrient molecules into body; secretes digestive hormones into blood

large intestine

absorbs water and salt to form feces

rectum

stores and regulates elimination of feces

salivary glands

moisten food

Parotid

Sublingual

Submandibular

Produce and secrete amylase – enzyme that initiates starch digestion,

tongue

striated muscle; helps mix food; forms food into a bolus

pharynx

Where digestive and respiratory passages come together; Soft palate closes off nasopharynx

Epiglottis

Covers opening into trachea

• Keeps food from air passages (most of the time)

peristalsis

Rhythmical contraction to move contents in tubular organs

chyme is emptied into

small intestine over 2.6-hour period

rugae

deep folds in the stomach

hiatal hernia

upper part of stomach bulges through diaphragm; can lead to gastroesophageal reflux disease

How common:

15 – 20 % of population

50% over 50

70% of people 70+

rugae disapear when/as

the stomach fills to an approximate volume of one liter: Can increase 20X in size (empty = 2.5 oz ---- full = 1 quart 32 oz)

epithelial lining of the stomach has

millions of gastric pits, which drain gastric glands

chief cells secrete

Pepsinogenwhich converts to pepsin, a hydrolytic enzyme, that acts on protein to produce peptides when in contact with HCL.

parietal cells secrete

H and Cl ions that form HCL (pH 1.5 to 2.5)

stomach epithelial cells secrete

protective mucous layer

Drugs reduce stomach acid by

interacting with parietal cells

Pepcid (Famotidine)

blocks histamine receptor, thus inhibits production

prilosec (omeprazole)

stops the proton pump from pumping thus, inhibits release

how long is the small intensine?

about 22 feet

duodenum of the small intestine

Digestion. Bile duct (gall bladder/liver) and pancreatic duct (bile salts and enzymes)

enter small intestine (1 ft)

Jejunum

Further digestion and most absorption of nutrients (~90%) (8 ft)

illium

Vitamin absorption and bile salt reabsorption (10 ft)

In the Duodenum…

Pancreatic fluid containing sodium bicarbonate (NaHCO3) and enzymes enter to neutralize acids and aid further digestion

Bile enters from

gall bladder to emulsify fats

The pancreas is an

Exocrine gland (product released through a duct)

• Produces pancreatic juice and digestive enzymes into the duodenum

Pancreatic amylase

digests starch to maltose

Trypsin (tryosinogen)

digests protein to peptides

Lipase

digests fat droplets to glycerol and fatty acids

Epithelial cells of intestine

also produce enzymes

• These complete digestion of peptides and sugars

bile is porduced in the

Liver

the gallbladder stores

bile

the bile duct

delivers bile to the duodenum

gallstones

hardened deposits of the gallbladder