Science 8 4th Quarter Reviewer Notes

Digestive System

can be divided into the alimentary canal and the accessory organs.

Alimentary Canal

Continuous muscular tube around 9 meters in length.

Mechanical Digestion

refers to the physical breakdown of food into smaller particles by chewing action of the teeth.

Chemical Digestion

refers to the enzymatic breakdown of the chemical bonds in larger and more complex molecules into simpler ones.

Three (3) different organs in the mouth:

• Teeth

• Tongue

• Salivary glands

Teeth

pairs of hard bony structures

tongue

muscular organ in the mouth that serves as taste or gustatory organ.

Taste buds

receptors that are scattered all over the tongue’s surface.

5 kinds of taste:

• Sweet

• Sour

• Salty

• Bitter

• Umami

Umami

Japanese word for delicious or savory taste

Salivary glands

secrete the slightly alkaline aqueous fluid called saliva

Saliva

moistens the mouth, softens food, and aids in the chemical digestions of starch.

three main paired salivary glands in the oral cavity;

• submandibular

• sublingual

• parotid glands

submandibular glands

located under the lower jaw

sublingual glands

can be found beneath the tongue

parotid glands

found in front of each ear.

ptyalin or alpha-amylase

speeds up the chemical digestions of starch into simpler carbohydrates

Esophagus

10 inch-long, smooth muscular tube that channels food into the stomach.

Peristalsis

rhythmically to push the bolus or mass of food downward in the process called

stomach

hollow smooth muscular organ that is located just below the diaphragm

stomach volume in milliliters

when stomach is empty, the volume is 75 milliliter but it can expand to 1000 milliliter when full with food

Gastric juice

mixture of water, gastric acid (hydrochloric acid), the enzyme pepsin, and mucus

Gastric Acid

Creates an acidic pH of around 2.50 to activate the digestions of protein by the enzyme pepsin

Chyme

it takes 4 hours for our stomach to turn ingested food into a soupy mixture called

small intestine

narrow convoluted muscular tube, with a length of 6 meters and diameter of 2.5 centimeters

Duodenum

first region of the small intestine where most of the calcium and iron ions are absorbed

Jejunum

sugars, amino acids, and fats at predominantly absorbed.

Ileum

vitamin B12 and bile salts are primarily absorbed

Villi

small intestine has millions of convoluted projects.

Microvilli

each of which has even tinier finger-like projections

Capillaries

beneath the single layer of cells in the villi are numerous capillaries that pass the nutrients into the circulatory system.

Pancreas

• lies horizontally across the posterior wall of the abdomen.

• Considered as a conglomerate gland

Acrinar cells

release bicarbonate ions and digestive enzymes into the small intestine

enzymes are

• lipases

• amylase

• peptidases

  which speeds up the breakdown of:

• fats, starch, and proteins.

Islets of Langerhans

endocrine cell pockets of different cells types that release different endocryne hormones

alpha-cells

releases glucagon

beta-cells

releases insulin

insulin

increasses and decreases blood glucose level

glucagon and insulin

said to be antagonistic hormones

liver

largest internal organ

liver’s four general functions

• digestive

• metabolic

• storage

• blood cell regulation

bile salts

emulsify fats into tiny droplets

temporarily stored in the gall bladder

gall bladder

small hollow pear-shaped organ

glycogen

serves as storage form of glucose in humans and animals

liver’s important storage organ for:

• iron

• vitamin A

• vitamin B12

• vitamin D

Kupffer cells

destruction of pathogens by the action of specialized macrophages are called

large intestine

also called the colon or large bowel

5 feet or 1,5 meters in length

appendix

is found at the lower end of the caecum

Feces

made up of waste materials such as undigested food, digestive juices, bacteria, and mucus