Download Lecture 7

Breathing, Circulation &
Digestion
The importance of
pressure, diffusion and
anatomy
Lung Structure
• Spongy – elastic
• Very large surface
area
• Bronchi branch to
form smaller
bronchioles
• Bronchioles end
in grapelike
bunches of alveoli
– formed of
alveolar sacs
• >300 X 106 alveoli
per human lung
Surface Area to Volume Ratio
1 cm
V = 1 cm* 1cm*1 cm = 1 cm3
SA = 1 cm*1cm/side =
1cm2/side
6 sides: total = 6 cm2.
SA:V = 6:1
½ cm
V = ½*½*½*8= 1 cm3
SA = ½ cm*½ cm/side = ¼
cm2/side
6*8 sides: total = 12
cm2.
SA:V = 12:1
Common misconception
• The force of air coming into the lungs
causes lungs to expand or…
• Without the incoming air, the lungs won’t
expand, and if the lungs don’t expand,
neither can the chest.
What physical property affects a gas?
•
Gases within a given volume exert
pressure against surfaces.
• What is pressure?
– Force/Area
=
N/m2
Snow example
• Snow is a weak supporting structure but
spreading weight over a larger surface
area can allow it to support you…..snow
shoes
Balloon
P=F/A
Relationship of Volume to Pressure
Volume
increases
what
happens to
the
pressure
exerted by
a gas?
Inhalation
higher
low
Increased volume
lower pressure in the
lungs - Atmospheric
pressure now greater
than lungs
Diffusion
CO2 Low
O2 Low
CO2 High
Tissue
O2 Low
CO2 High
Capillary
O2 High
Capillary
Lung
O2 High
CO2 Low
Functions of the circulatory
system?
THE CIRCULATORY
SYSTEM
Besides transporting
oxygen and nutrients
that sustain body
processes, the
circulatory system
transports waste
materials produced by
cells.
Function of a Digestive System
• Dissasembly process
• Large chunks to smaller molecules
• Ultimately, these small molecules are
taken up by circulatory system and
distributed to cells
The Four Stages of Food
Processing
• Ingestion
– Is another word for eating
• Digestion
– Is the breakdown of food to small molecules
• Absorption
– Is the uptake of the small nutrient molecules by
the body’s cells
• Elimination
– Is the disposal of undigested materials from the
food we eat
• Mechanical digestion
– 1st step in the process of digestion
– Involves physical processes like chewing
– How is this done?
• Teeth
• Also adds
water
for chemical
Increases
the
surface
toreactions
volume
ratio
of food particles but it does not break
the chemical bonds within a food
molecule
Role of Saliva
• Salivary glands made up of three glands
• Amylase is responsible for initiation of
starch breakdown
• What’s starch?
Esophagus- delivers food to stomach
Nerve endings in
throat/pharnx
cause esophagus
walls to contract
which move the
bolus to the
Stomach.
Epiglotis stops
food from
entering trachea,
acts like a one
way flap.
Stomach- specialized structure for
further chemical digestion
Gastric juices
and enzymes
mix with food.
These target and
breakdown
proteins and
lipids.
This mixture
now leaves
stomach thru
pyloric sphincter
and enter small
intestine.
Small intestine – Primary site of
absorption of digested molecules
More enzymes are
produced in small
intestine as well as……..
Hormone secretion that
regulates release of food
from stomach and…….
The release of secretions
from the pancreas and
liver.
Duodenum-upper portion still
receives some digestive enzymes
– Is the first part of the small intestine
– Receives digestive agents from several organs
Liver produces
bile that is
stored in
Liver
gallbladder. It
is then pumped
into doudenum
to reduce the
size of fat
Gallbladder
globules in a
process called
emulsification.
Pancreasneutralizes
acids from
stomach by
production of
bicarbonate
ions.
Bile
Stomach pH?
Bile
Acid chyme
Doudenum pH?
Pancreatic juice
Duodenum of
small intestine
Pancreas
• The jejunum and ileum
– Are parts of the small intestine
– Are specialized for absorption
Nutrient
absorption
Nutrient
absorption
Blood vessels
Microvilli
Epithelial
cells
Interior of
intestine
Muscle
layers
Villi
Blood
capillaries
Lymphatic
vessel
Epithelial cells
Nutrient
absorption
Intestinal wall
Villi
Colon: Large intestine- absorption
of water.
Water reabsorption.
Bacteria further
breakdown undigested
food.
Bacteria add vitamins.
Colon: rectum – specialized region
for temporary storage
Anus –
exit from
digestive
systemseparate
exit from
the
urogenital
system
The End