Download Digestive System and Nutrition - Chapter 26

Digestive System and Nutrition - Chapter 26
All animals are heterotrophs and need organic molecules as food. We need food to get nutrients and
energy.
Body Mass Index (BMI) is a measure to understand desirable body weight for a person of certain height.
It is considered overweight if its value is above 25. Formula used to calculate BMI is:
Body Mass Index = body weight in Kg / height in m2
Cnidarians and flat worms have incomplete digestive system with one opening mouth. Actually this
cavity acts as a gastrovascular cavity and serves as both digestive and vascular system.
Complete digestive tract
Round worms evolved complete digestive system with both mouth and anus. It has a tube within tube
design.
Most animals including humans have a digestive tract and associated glands.
Human Digestive System
Humans have digestive tract with: mouth  mouth cavity  pharynx  esophagus  stomach 
duodenum  small intestine  large intestine  anus. The associated glands are salivary glands, liver,
and pancreas.
Liver and Pancreas
Liver: is the largest gland in body. It stores its waste bile in Gall Bladder. Bile is released into duodenum
and helps in digestion of fats. Liver secretion, bile, does not have any enzymes in it. Liver absorbs excess
glucose from blood and release it back when needed.
Pancreas: is the 2nd largest gland in human body. It secretes pancreatic juice into duodenum. The juice
changes the acidic food from stomach into slightly basic food. It is very rich in digestive enzymes and
help in digestion of starch, fats, proteins and nucleic acids.
4-stages of food-processing
Ingestion is the eating of food by an animal.
Digestion is mechanical (chewing and churning) and chemical (hydrolase enzymes) breakdown of food.
The polymers like starch, proteins, and nucleic acids are broken down to monomers like glucose, amino
acids and nucleotides. Bigger molecules like fats are broken into fatty acids and glycerol.
Absorption is entry of food from alimentary canal into blood.
Elimination is removal of undigested food from anus in the form feces.
Digestion
Digestion in oral cavity: Salivary glands add saliva to lubricate and bind the food in mouth cavity. Saliva
has Amylase enzyme and starts digestion of Starch.
-salivary amylase
Starch------------------------ --------- Maltose (sugar)
Pharynx: Both food pipe = esophagus and wind pipe = trachea open in Pharynx. Air from the nasal cavity
enters trachea. A ball of food from oral cavity is swallowed into esophagus. During swallowing of food
epiglottis covers the glottis, the opening of trachea. Uvula a free hanging part of Palate blocks the
internal opening of nasal cavity.
Digestion in Stomach: Gastric glands secrete HCl (hydrochloric acid) and enzyme Pepsin and change
food into Chyme an acidic semi-fluid. Hydrochloric Acid kills bacteria in food and activates the enzyme
pepsin. Pepsin starts the Protein Digestion in stomach.
Diabetes Mellitus
Pancreas also secretes 2 hormones Insulin and Glucagon that control the amount of glucose in blood.
Insulin lowers blood glucose and glucagon raises it.
Diabetes Mellitus: T1DM is caused due to deficiency of insulin (5%). It can be can be cured with insulin
injections.
T2DM is caused due to malfunction of receptors for insulin (95%) and cannot be cured with insulin
injections.
Recap 1 Digestive System
1. Alimentary canal has only mouth in ------------- and --------------2. ---------------- glands open into mouth cavity
3. --------------- is a common passage for air and food
4. During swallowing of food --- covers glottis and --- covers nasal cavity
5. Stomach leads to 1st part of small intestine named -------6. ----- is the largest gland and ---------- is the 2nd largest gland in body
7. 4 kinds of teeth in mammals are -----, ----, premolars and ---------8. Most digestion takes place in --------------- -----------9. Feces formation takes place in ----------------
--------------
10. Water soluble vitamins include -------------- and ------------11. Fat soluble vitamins are vitamin ------, -------, ----------, and ---------12. We need to eat small quantity of -----, -----, and ----- fats.
13. ---------% calories in diet should come from fats.
14. Fruits and vegetables provide ---, -- that reduce the chance of cancer