Digestive System (bio test 4)

Define: herbivores, carnivores, omnivores

• (cattle, snails), dine mainly on plants and algae

• (lions, spiders), mostly eat other animals

• (humans, cockroaches), consume plants and animals

Food processing stages

1. ingestion

2. digestion

3. absorption

4. elimination

Alimentary canal

compartments for digestion that run from the mouth to the anus

Role of the oral cavity (mouth)

• food in ingested/chewed here

• mechanical digestion (chewing, smashing, grinding)

• Tongue:

  • tastes, shapes food into a ball called bolus, moves it toward the pharynx

Pharynx

• the throat

• opens to two passageways: the trachea and the esophagus

• moves food into the esophagus

• food is pushed by the tongue

Peristalsis

involuntary wave-like muscle contractions that propel food and liquid from your throat down into your stomach

What are sphincters?

• where muscles meet other muscles

• where food is moved into and out of the stomach

Small intestine

• nutrient absorption and chemical digestion occurs

• Folds of the intestinal lining and finger-like villi (with microscopic microvilli) increase the area across which absorb nutrients move into capillaries and lymph vessels

Large intestine

• undigested material moves slowly through here

• some bacteria in colon produce vitamins

• the large intestine absorbs these vitamins and water into the bloodstream —> helps form feces

• Diarrhea: too little water “remains” in the large intestine

• Constipation: too much water “remains” in the large intestine

Anus

waste is expelled through here

Epiglottis

seals off the trachea to keep food from entering your windpipe

Stomach

• secretes gastric juices, pepsinogen, and HCI

  • Gastric juices: made up of protein-digesting enzyme, mucus, and strong acid

  • pepsinogen: protects cells of the gastric glands

  • HCI: converts some pepsinogen to pepsin

  • pepsin: begins to digest proteins

apendix

vestigial structure

gallbladder

stores bile

Liver

• produces bile to emulsify fats + detoxify blood from the intestines

• regulates nutrient levels in the blood, detoxifies alcohol and drugs, and synthesizes blood proteins

Bile

• a digestive fluid that breaks large fat droplets into smaller droplets (emulsifies fats), making them easier for enzymes to digest

• also detoxifies blood

• produced by the liver

• stored in the gallbladder

Path of food/chyme through the alimentary canal

1. oral cavity

2. esophagus (pass by epiglottis)

3. cardiac sphincter

4. stomach

5. pyloric sphincter

6. duodenum

7. jejunoileum

8. ileocecal sphincter

9. large intestine/cecum

10. rectum

11. anal sphincter

chyme

mixture of partially digested food and stomach acid that moves from the stomach to the small intestine

Enzymatic digestion in the small intestine

• carbs: amylase, maltase, sucrase, lactase

• proteins: trypsin, various peptidases

• nucleic acids: nucleases

• fats: bile salts, lipase

rectum

feces are stored here

What features of the small intestine allow it to efficiently absorb nutrients?

• villi and microvilli - tiny projections on inner wall of the small intestine

• they greatly increase the surface area across which nutrients are absorbed

• also increase rate of nutrient absorption

Pancreas

secretes digestive enzymes - carbs, proteins, fats, and nucleic acids