Chapter 5: Nutrition in human

What is nutrition in human? the process in which organisms obtain food and energy for growth, repair and maintenance for the body

What is absorption? the process whereby digested food substances are absorbed into the body cells

What is digestion? the process whereby large food molecules are physically and chemically broken down into smaller, soluble food molecules that can be absorbed into the body cells

What is peristalsis? the rhythmic, wave like muscular contraction in the wall of the alimentary canal

Effects of alcohol consumption on the brain and body

"Wet brain": dementia caused by brain damage

shrinkage of brain volume: affects memory/ reasoning

slurred speech/ blurred vision/ poor muscle coordination

affects fetus' brain: affecting lifelong, physical, mental, behavioral problems

slow down reaction time

reduced self control

cirrhosis (disease in which liver cells are destroyed, leading to liver failure and eventually death)

Social implications on alcohol consumption

exhibit violent behavior (especially towards family)

tend to commit crimes

neglect their work and family

Structure of human digestive system and its functions

Oesophagus

Stomach

Mouth (buccal cavity)

Small intestine

Absorbtion function

Digestive function

Structural adaptation

(b) tongue

(c) salivary glands

(a) teeth, which consist of incisors, canine, premolar and molar

Function

(a) used for chewing of food (physical digestion) which will increase surface are to volume ratio for faster rate of chemical digestion by enzymes --> hydrolysis

(b) to roll food into bolus/ boli for easy swallowing

(c) produce saliva which consists mainly of water and salivary amylase

(i) water lubricates the boli for easy swallowing

(ii) salivary amylase speeds up the hydrolysis of starch into maltose

Function

Structural adaptation

the wall of the oesophagus consists of circular and longitudinal muscle

the circular and longitudinal muscles that make up the walls of the oesophagus, stomach, small and large intestines, and rectum. These muscles carry out peristalsis** which will move the food along the alimentary canal

muscle and lumen size ratio

circular muscle contract, lumen size decrease

longitudinal muscle contract, lumen size increase

Structural adaptation

two rings of muscles (cardiac sphincter and pyloric sphincter) are found at two ends of the stomach

gastric pits consists of cells that produce gastric juice (pepsin and hydrochloric acid)

a bag like organ which consists of a 3rd layer of muscle called oblique muscle in addition to circular and longitudinal muscle

structural adaptation

function

(b) intestinal glands found on the epithelium layer of the small intestine inner wall produces intestinal juice

(c) pancreas produces pancreatic juice and transports it to the small intestine via the pancreatic duc

(a) the small intestine is 6-7m long. It consists of duodenum, jejunum, and iluem

(d) liver produces bile. bile stored is in the gall bladder and tranported to the small intestine via bile duct

(a) long small intestine increases time for complete digestion and absorbtion

(b) functions of enzymes found in intestinal juice

(d) What is the function of bile?

(c) functions of enzymes found in the pancreatic juice

source: epithelial cells

protease

maltase

lipase

break down fats to fatty acid and glycerol

break down polypeptides to amino acids

break down maltose to glucose

source: pancreas

protease

pancreatic amylase

lipase

break down proteins to polypeptides

break down starch to maltose

break down fats to fatty acids and glycerol

Bile salts emulsifies fats. They lower the surface tension of the fats, reducing the attractive forces between the fat molecules. This causes the fats to break into tiny fat droplets suspended in water forming an emulsion. Emulsification increases the surface area to volume ratio of the fats, speeding up the digestion by lipase

structural adaptation

function

1: S.I is 6-7m long

2: Inner wall is thrown into folds

3: Numerous villi present on inner walls (finger like projection)

4: Presence of microvilli on villi

5: Presence of mitochondria in the epithelial cells

6: Presence of dense network of blood capillaries

2,3,4: Increase S.A. for absorbtion for increased rate of aerobic reaspiration

5: Numerous mitochondria = increased rate of aerobic respiration = increased amount of energy for faster rate of active transport

1: Increases time for complete absorbtion and digestion

6: Bring/ transport food substances to and away from the villi at a faster rate creating a steep concentration gradient of food molecules between the blood and villi and the content of the S.I. Hence increasing the rate of absorbtion of food molecules

What is deamination? (occurs in the liver): the process by which amino acid groups are removed from amino acids and converted to urea

Regulation of blood glucose concentration

What is the function of liver in assimilation? the liver produces and secretes bile which is stored in the gall bladder. this helps the physical digestion of fats

When blood glucose rises above normal

When blood glucose falls below normal

Insulin is secreted by pancreas

Liver converts glucose into glycogen for storage

Blood glucose concentration decreases back to normal

glucagon is secreted

Liver converts glycogen into glucose to be released into the bloodstream

Blood glucose concentration increases back to normal