1. Digestive System

2. Purpose
The digestive system is the organ system that breaks down food into carbohydrates, proteins, fats, vitamins, and nutrients for the body to use for energy

3. Nutrients
A nutrient is a substance that the body breaks down and uses to grow, repair, and function

4. 6 Processes of Digestion
Ingestion
Secretion
Mixing & Movement
Digestion
Absorption
Excretion

5. Alimentary Canal Also called the Gastrointestinal (GI) Tract
A long, hollow, twisted, and coiled tube that runs through the body
It includes:
Mouth, throat, esophagus
Stomach, small intestine, large intestine, rectum, anus

6. 1. Ingestion
Food enters the digestive system through the mouth
eating

7. 2. Secretion
Process by which a substance is released from an organ or gland to assist in digestion
The body secretes almost 2 gallons of digestive fluids per day!
Saliva
Mucus
Hydrochloric acid
Bile

8. Saliva: produced by salivary glands
Watery mixture with digestive enzymes
Enzymes speed up a reaction
Speeds up the break down of food into simpler substances
Moistens food

9. Hydrochloric acid
strong acid that breaks food down in the stomach

10. Mucus Lubricant: helps food to slide down esophagus easily
Protection: mucus lines
the stomach walls to
protect it from the strong
acid inside

11. Bile Produced by liver Stored in gallbladder Released into the
small intestine
Thick green fluid
Breaks down large
fat droplets in the

12. 3. Mixing & Movement Mixing begins with the chewing muscles
in the mouth
Tongue(large muscle) helps to form the bolus: soft, round mass of chewed food

13. 3. Mixing & Movement (cont)
The tongue helps to move the
food into the pharynx
Movement continues as the food
moves through the digestive tract

14. 3. Mixing & Movement (cont)
Most of the mixing happens in the stomach
Food is mixed with gastric juice
Gastric juice is a mixture of mucus, hydrochloric acid and enzymes, especially pepsin

15. Protease A protease is an enzyme that breaks down proteins
Pepsin is a protease in gastric juice

16. 4. Digestion
Digestion is the actual breaking down of complex food into basic building blocks

18. 2 types of Digestion
A)Chemical digestion: the breakdown of food by chemical means through enzymes
It happens in
The mouth (saliva)
Stomach( protease & hydrochloric acid)
Small intestine (enzymes from pancreas and bile from gallbladder)
Large intestine (gut flora)

20. Gut Flora
Symbiotic bacteria that break down some materials

25. 2 types of Digestion (cont)
B) Mechanical Digestion: the physical breaking down of food.
It involves: chewing, churning,
& segmentation

26. 5) Absorption
This is the process by which substances are passed from the digestive tract into the blood.
The blood transports them to other parts of the body
Mostly occurs in the small
intestine
Nutrients are absorbed into
capillaries

27. 6)Excretion This is the removal of waste products
Digestive waste products
accumulate in the large intestine
Remaining water is absorbed
Solid wastes (feces) are
stored in the rectum and
eliminated through anus.

28. Organ Systems related to Digestion
1) Nervous System: prepares for food by contracting stomach or triggering salivary glands

29. Organ Systems related to Digestion (cont)
2)Endocrine System: releases hormones that regulate body functions.
Some of these hormones determine production of digestive juices, control stomach muscle contractions, control absorption rate of nutrients

30. The Mouth
Both chemical and physical digestion takes place in the mouth
It contains the teeth, tongue, and salivary glands

31. Teeth
Adult jaw contains
32 teeth
4 types of teeth

32. Incisors
8 total (4 top, 4 bottom)
Chisel shaped
Biting large pieces.

33. Cuspids Also called canine teeth 2 upper, 2 lower Cone-shaped
For grasping &
tearing food

35. Bicuspids Also called premolars 4 top, 4 bottom Flat surfaces
For grinding food

37. Molars
Similar to premolars, but larger
6 on bottom, 6 top

39. A tooth is made of…. Enamel: hard tissue on outside of tooth
Crown: the part of tooth above gum
Root: part of tooth that anchors it into gum
Cementum: a thin, bony material that fixes the root to the jaw
Dentin: largest part of tooth, hard bone-like tissue under enamel

41. Salivary Glands Three sets of glands
Release saliva for chemical digestion

42. Tongue Tongue: primary organ of taste
Taste buds: send taste information
to brain where it is processed
Shapes food into the bolus and
directs it into the pharynx

43. Esophagus
Movement of muscle contractions which push the food is called peristalsis

44. Structure of the Stomach
Hollow, muscular sac
Below the diagram, left side
Can expand to about 2 liters
Food remains in stomach for 1-2 hours
Muscle contractions cause the bolus to mix with gastric juice
Now the bolus is called chime.

45. Small Intestine Long, hollow, muscular tube Between 18-23 feet
Length provides surface
area and time for the absorption
of nutrients.

46. Villi Small folds in the small intestine
Contain artery, vein, and capillaries
The capillaries absorb nutrients into the blood

48. Duodenum: entrance to small intestine from stomach
This is where the bile and other enzymes from pancreas an gallbladder

50. Large Intestine Has a larger diameter than small intestine
Less than 5 feet long
Function: 1) to absorb any remaining water, electrolytes, and vitamins in the colon
2) remove wastes through rectum and anus.

51. Liver
2nd largest organ
Under right rib cage