Nutrition in Mammals

Chapter 6

LESSON RECAP

What did we learn the previous lesson?1. Introduction to Nutrition in

Mammals2. Organs in the Mammalian Digestive

system3. Detailed examination of - Oesophagus,

- Stomach- Small intestines

4. Adaptations of the intestines for absorption

• Two layers of smooth muscles:

longitudinal & circular muscles

What happens in the Oesophagus?

Peristalsis-is the Wave like contraction of the walls of the gut to move food down from mouth to stomach

Circular muscle contracts; lumen constricts

Longitudinal muscle relaxes

ANTAGONISTIC MUSCLES

Demonstration

• Distensible = can stretch & expand• Send “Full” signal to brain• Numerous pits with gastric glands• Pyloric splincter = ring of muscle connecting

the small intestines.

*StomachStructure of Stomach

What happens in our Stomach?

•Peristalsis occurs in the stomach

What happens in the Stomach?

Peristalsis- Wave like contraction of the walls of the gut to move food down from mouth to stomach

Small Intestines – Last chance to digest!

Demonstration

How does the movement of the intestinal wall look like?

How do villi help to increase rate of absorption in the small intestine?

How does the villus structure help to increase rate of absorption in the small intestine?

OR

Does surface area matter for absorption?

If the small intestines were only a hollow tube…

0.5m2

200.0m2

Adap

tatio

n of

the

smal

l int

estin

es Increase Surface Area

Inner walls have numerous folds Lined with vili Microvilli on villi

Adaptations of the intestinal wall

One-cell thick epithelium

Numerous blood vessels to

maintain concentration

gradient.

Increase Surface area

How is the intestinal wall adapted for absorption?

Thin membrane – 1 cell thick

Epithelium-the inner and outer tissue covering digestive tract organs.ukhealthcare.uky.edu/patient/glossary/glossary-e.htm-a type of tissue which lines a surface in the body.www.di.uq.edu.au/sparqglossary

Adap

tatio

n of

the

smal

l int

estin

es

One-cell thick epithelium

Increased intestinal surface area

1 cell thick epithelium

Many capillaries carry substance awayEach villus has a lacteal/lymphatic capillary surrounded by blood capillaries. Continuous transport of digested food substances awayAd

apta

tion

of th

e sm

all i

ntes

tines Numerous capillaries to maintain

concentration gradient

• A concentration gradient is maintained at the villus by the continual transport of digested food substances away from the villus.

Q. How is Concentration gradient maintained at the site of the intestinal

villus?

Adap

tatio

n of

the

smal

l int

estin

es

Absorption at the small intestines villus

• Glucose & amino acids enter into blood capillaries via diffusion & active transport

• Glycerol & fatty acid diffuse into the epithelium, then combines back to fat molecules when they enter lacteal

• Water & mineral salts also absorbed.

How does absorption take place?

Summary

1. Introduction to Nutrition in Mammals

2. Organs in the Mammalian Digestive system 3. Examined:

• Oesophagus• Stomach• Small intestines

4. Adaptations of the intestines for absorption

Today’s Guest

Mr. Liver

Q. HOW ARE FOOD SUBSTANCES TRANSPORTED AND UTILIZED?CHAPTER 6 PG 105

Good job! You’re done with all the goodies?

Pass them to me and I’ll re-distribute!

Liver Boss, I’m done with absorbing all

the nutrients. My villus is rich. What do I do with them now?

Huh? What is air-mail?There are no planes

around the area. You need to ship the ‘goodies’ to me

But you’re quite a distance away,

Can I send them to you by air mail?

HEPATIC PORTAL VEIN

Q. What are the ‘goodies’ to be transported?

• Glucose• Amino acids

Fate of Glucose

• Redistributed• Excess return

So what do I do now with the excess glucose?

Let’s check out for laborers in the market

In the Blood Market….

glucagon

insulin

glucagon

insulinglucagon

insulin

glucagon

From pancreas…