digestive system

1. Distinguish between autotrophs and heterotrophs.

Autotrophs— make their own organic food
Heterotrophs— obtain food by consuming other organisms/organic material

2. Distinguish between herbivores, carnivores, omnivores.

• Herbivore → eats plants

• Carnivore → eats animals

• Omnivore → eats both plants + animals

3. Recognize the essential nutrients.

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4. State the four stages of food processing.

Ingestion→ Transportation and storage—>Digestion (Chemical and mechanical)—> absorption —> elimination

whats ingestion

Taking in of food

digestion

Process of breaking down food small enough to be absorbed Mechanical and chemical breakdown

absorption

Nutrients enter body fluids

Whats elimination

Removal of undigested material

Intracellular vs extracellular digestion

Intracellular— within the cell
— Ex. Protozoans(paramecium) and white blood cells
Extracellular- outside of cells; within a cavity
— Ex. hydra; human and digestive tract

6. Describe the mammalian digestive system, namely the human, and list the parts included

The human digestive system consists of the GI tract plus accessory digestive organs/glands.
— Mouth → pharynx → esophagus → stomach → small intestine → large intestine → rectum → anus
Accessory structures include things such as the salivary glands, liver, gall bladder, and pancreas.

7. Recognize and label the parts of the human digestive system.

8. Mechanical vs. Chemical Digestion

Mechanical digestion → physically breaks/processes food.

Chemical digestion → enzymes chemically break large food particles into smaller molecules that can be absorbed.

what are the 5 forms of mechanical digestion

Mastication(chewing)
swallowing
peristalsis
churning
emulsification

10. Describe the oral cavity and the processing of food.

ingestion

Mastication using teeth

Begins swallowing, aided by the tongue

Receives saliva from salivary glands

Identify the 3 salivary glands

parotid
submandibular
sunlingual

state the composition and action of saliva.

Slightly acidic secretion

Largely water: moisture allows for taste

Mucus: lubrication

Lysozyme: protection against bacteria

Amylase: initiates carbohydrate digestion

Define bolus

Swallowed mass of food.

Conducts food, known as bolus, from pharynx to stomach

Describe the three parts of the pharynx

Nasopharynx → upper

Oropharynx → middle

Laryngopharynx → lower

pharynx and its functions

Common passageway for the digestive and respiratory systems
- secretes mucus for lubrication

4. Describe the swallowing process.

The tongue helps initiate swallowing.

During swallowing, food moves from:

Oral cavity → pharynx → esophagus

The epiglottis helps keep food out of the respiratory tract.

State the location and function of the epiglottis.

At junction, epiglottis closes over opening into respiratory tract while swallowing

This prevents food from entering the respiratory pathway.

Describe the esophagus and its function

— Conducts food, known as a bolus, from the pharynx to the stomach

— Moves food by peristalsis

— Secretes mucus

— Passes through the neck/thoracic cavity, and then the diaphragm to the stomach

— Lies dorsal to the trachea

Peristalsis

Muscular movement that moves food through the digestive tract.

Peristalsis → moves the bolus (swallowed mass of food) toward the stomach.

Describe the stomach

cardiac sphincter; pyloric sphincter; fundus; body; rugae; greater and

lesser curvatures.

Cardiac sphincter

controls passage of bolus from esophagus → stomach

(Chyme)

Fundus

→ upper expanded region

Body

Main portion

Rugae

folds lining stomach
Gastric glands

Pyloric sphincter

controls passage of food from stomach → small intestine

Greater curvature

outer

Lesser curvature

inner

19. Chyme

Once the bolus enters the stomach and is processed, it is called chyme.

🧠 Bolus → stomach → chyme

Describe the composition and function of gastric juice

The function of gastric juice is that it’s very adicic
HCl; pepsinogen; pepsin;

mucus; rennin.

HCI

• activates inactive pepsinogen to pepsin

pepsinogen

Inactive precursor of pepsin.

Pepsin

• Breaks down proteins into polypeptides

Mucus

• protection
  protects stomach lining

Rennin

solidifies milk

whats the intrinsic factor

• helps Vit B12 absorption

21. Why Doesn't the Stomach Digest Itself?

Two major protections:

1. Pepsin is initially secreted in an inactive form

2. Stomach lining is protected by mucus

ulcer

an open sore/damage in the lining of the stomach or digestive tract.

describe the small intestine, its 3 parts, and its function

About 6.5m long and 2.5 cm diameter
duodenum
jejnum
ileum

Duodenum

receives secretions from accessory glands: liver, gallbladder and pancreas

Ileum

JOINS with the LARGE intestine+ ileocecal valve leading into the cecum+ appendix at the end

Describe the villi and their function

The small intestine is lined with millions of villi.

Their importance becomes especially clear during absorption: villi provide a large surface area, with good blood and lymphatic supply.

🧠 Villi = increase surface area for absorption

Describe intestinal juice

slightly alkaline

intestinal juice and the action of the enzymes.

Carbohydrates

• Maltase

• Sucrase

• Lactase

Proteins

• Peptidases

Nucleic acids

• Nucleases

Describe the pancreas (Endocrine)

Islets of Langerhans

Insulin: decreases blood sugar

Hypofunction: diabetes mellitus
(Too little insulin → diabetes mellitus → ↑ blood sugar)

Glucagon: increases blood sugar

Describe the pancreas (exocrine/digestive)

Produces pancreatic juice, which enters the duodenum.

whats the relationship between insulin and glucagon

Insulin ↓ glucose

Glucagon ↑ glucose

Describe pancreatic juice containing

Bicarbonate, Proteolytic enzymes, Carbohydrate enzymes, Lipase

Bicarbonate

→ helps neutralize acidic chyme

Proteolytic enzymes

protein digestion
secreted inactive by the pancreas
activated in small intestine initially by enterokinase

Carbohydrate enzymes

→ completes carbohydrate digestion
in the pancreas

Lipase

→ lipid digestion
pancreas

Explain why the proteolytic enzymes are secreted from the pancreas in an inactive form and

how they are activated.

Proteolytic enzymes are secreted inactive → activated in the intestine, initially by enterokinase.

This prevents them from acting before reaching their proper site of action.

Describe the liver and its functions.

29. Liver Functions

The liver:

• Is a large gland beneath the diaphragm

• Produces bile

• Forms/stores glycogen

• Detoxifies

• Destroys red blood cells

• Stores fat-soluble vitamins

  • Synthesizes blood proteins

30. Describe the gallbladder

• Sac on under surface of liver

• Stores and concentrates bile

gallbladder and its role in digestion.

— the The cystic duct leads from the gallbladder and combines with the hepatic duct from liver
— forms common bile duct, which leads into the duodenum

Describe the composition of bile and the process of emulsification.

Bile is produced by the liver.

Its digestive role:

Emulsifies fats → breaks them into smaller fat globules

Important:

Bile does NOT contain digestive enzymes.

Your professor calls emulsification a mechanical action.
🧠 Bile = breaks big fat globules → smaller globules

32. Describe how the secretions from the pancreas, liver, and gall bladder enter the duodenum.

Pancreas:
Produces pancreatic juice → enters the duodenum.

Liver:
Produces bile → hepatic duct

Gallbladder:
Stores bile → cystic duct

Then:

Hepatic duct + cystic duct → common bile duct → duodenum

Liver + Gall bladder → bile duct → duodenum
Pancreas → pancreatic juice → duodenum

Identify the main digestive enzymes and include site of secretion; site of action; substrate; products: Salivary amylase

Salivary glands Mouth Starch/carbohydrates Maltose

Identify the main digestive enzymes and include site of secretion; site of action; substrate; products: Pepsin

Stomach

Stomach

Proteins

Polypeptides

Identify the main digestive enzymes and include site of secretion; site of action; substrate; products: Rennin

Stomach

Stomach

Milk protein

Coagulated/solidified milk

Identify the main digestive enzymes and include site of secretion; site of action; substrate; products: Intestinal peptidases

Small intestine

Small intestine

Peptides

Amino acids

Identify the main digestive enzymes and include site of secretion; site of action; substrate; products: Trypsin

Pancreas

Small intestine

Proteins/polypeptides

Smaller peptides

Identify the main digestive enzymes and include site of secretion; site of action; substrate; products: Chymotrypsin

Pancreas

Small intestine

Proteins/polypeptides

Smaller peptides

Identify the main digestive enzymes and include site of secretion; site of action; substrate; products: Carboxypeptidases

Pancreas

Small intestine

Peptides

Amino acids

Identify the main digestive enzymes and include site of secretion; site of action; substrate; products: Pancreatic amylase

Pancreas

Small intestine

Starch/carbohydrates

Maltose

Identify the main digestive enzymes and include site of secretion; site of action; substrate; products: Pancreatic nucleases

Pancreas

Small intestine

Nucleic acids

Nucleotides

Identify the main digestive enzymes and include site of secretion; site of action; substrate; products: Pancreatic lipase

Pancreas

Small intestine

Fats/lipids

Fatty acids + glycerol

Summarize the digestion of carbohydrates: site of digestion and enzymes involved. (mouth, small intestine, pancreas)

Mouth

→ salivary amylase begins carbohydrate digestion

Small intestine

→ intestinal juice contains:

- Maltase

- Sucrase

- Lactase

Pancreatic juice

→ carbohydrate enzymes complete digestion.

Summarize the digestion of proteins: site of digestion and enzymes involved. (stomach, small intestine, pancreas)

Stomach

→ pepsin begins protein digestion

→ proteins → polypeptides

Small intestine

→ peptidases continue protein digestion

Pancreas

→ supplies proteolytic enzymes in inactive form, which are activated in the intestine.

Summarize the digestion of fat: site of digestion; action of bile; and enzymes involved.

Bile

→ emulsifies fats into smaller fat globules

Then:

Pancreatic lipase

→ digests lipids.

Bile = emulsifies

Lipase = digests

37. Recognize the mechanisms of absorption.

Absorption occurs through both:

• Passive transport

• Active transport

State the absorption that takes place in the oral cavity

Very little absorption

• Some drugs such as nitroglycerin

State the absorption that takes place in the Stomach

Absorbs:

• Alcohol

• Inorganics

• Some drugs

State the absorption that takes place in the Small intestine

Main organ of absorption DIGESTIVE SYSTEMPowerPoint

⭐ Small intestine = MAIN absorption organ

State the factors that make the small intestine a good organ for absorption.

— Large surface area (villi) and good blood and lymphatic supply (lacteals) where fatty acids and glycerol are absorbed

40. Describe the villus and the role of the capillaries and lacteal in absorption

Villi provide a large absorptive surface and have good:

• Blood supply

• Lymphatic supply
  lacteal as the lymphatic structure where fatty acids and glycerol are absorbed.
  capperliies absorb nutrients to the blood

🧠 Lacteal = fats

41. Discuss both neural and hormonal control of digestion and the role each play in the oralcavity; stomach and small intestine.

Oral cavity

Chemical + mechanical actions → stimulate saliva secretion

Stomach

Neural stimulation → presence of protein

Hormones also regulate digestion.

Small intestine

Hormones regulate intestinal, pancreatic, and gall-bladder secretions.

State the site of production, site of action, and function of the following hormones: gastrin;

Stomach Stomach Stimulates gastric juice

State the site of production, site of action, and function of the following hormones; Enterogastrone

Duodenum Stomach Inhibits gastric juice

State the site of production, site of action, and function of the following hormones; Secretin

Duodenum Pancreas Stimulates pancreatic juice high in bicarbonate

State the site of production, site of action, and function of the following hormones: Pancreozymin

Duodenum Pancreas Stimulates pancreatic juice high in enzymes

State the site of production, site of action, and function of the following hormones; Enterocrinin

Small intestine	Small intestine	Stimulates intestinal juice

State the site of production, site of action, and function of the following hormones; Cholecystokinin (CCK)

Duodenum

Gall bladder

Stimulates gall bladder

Describe the structure of the large intestine (colon): ascending, transverse; descending;

sigmoid colon.

Ascending → up right side

Transverse → across top

Descending → down left side

Sigmoid → S-shaped

Describe the junction of the small and large intestine: ileocecal valve; cecum; appendix

Ileum → ileocecal valve → cecum

The appendix is located at the cecum.

45. Recognize the human appendix as a vestigial organ.

Appendix = vestigial organ

Discuss the role of the large intestine: normal flora; reabsorption of water; elimination of

fecal material.

Normal flora

→ beneficial bacteria that synthesize vitamins

Reabsorption of water

Elimination of fecal material DIGESTIVE SYSTEMPowerPoint

47. Composition of Feces

Undigested food including cellulose

Bacteria

Cells

Bile pigments

Water

Inorganics

48. Diarrhea vs. Constipation + Laxatives

Diarrhea

Material passes through quickly → little time for water reabsorption

Constipation

Slow movement through digestive tract.

49. Rectum + Anus

Rectum → terminal portion of the large intestine.

Anus → terminal opening.

Your professor's slide gives the sequence:

Colon → rectum → anus.