Circulation and Gas Exchange

Page
12

Exhaled air passes over the vocal cords to create sounds.

Alveoli are wrapped by capillaries for GAS EXCHANGE.

Slide 75

Mammalian Respiratory System

Pharynx

Larynx

(Esophagus)

Trachea

Right lung

Bronchus

Bronchiole

Diaphragm

Heart

SEM

Left

lung

Nasal

cavity

Terminal

bronchiole

Branch of

pulmonary

vein

(oxygen-rich

blood)

Branch of

pulmonary

artery

(oxygen-poor

blood)

Alveoli

Colorized

SEM

50 µm

50 µm

Slide 76

Breathing Ventilates the Lungs by Inhalation and Exhalation of Air

Amphibians, such as a frog, ventilates its lungs by positive pressure breathing, which forces air down the trachea.

Mammals ventilate by negative pressure breathing, which pulls air into the lungs by varying volume / air pressure. Lung volume increases as the rib muscles and diaphragm contract.

The tidal volume is the volume of air inhaled with each breath. The maximum tidal volume is the vital capacity. After exhalation, residual volume of air remains in the lungs.

Slide 77

Negative pressure breathing: H --> L

Lung

Diaphragm

Air

inhaled

Rib cage

expands as

rib muscles

contract

Rib cage gets

smaller as

rib muscles

relax

Air

exhaled

EXHALATION

Diaphragm relaxes

(moves up)

Volume decreases

Pressure increases

Air rushes out

INHALATION

Diaphragm contracts

(moves down)

Volume increases

Pressure decreases

Air rushes in

Slide 78

How a Bird Breathes

Birds have eight or nine air sacs that function as bellows that keep air flowing through the lungs.

Air passes through the lungs in one direction only.

Every exhalation completely renews the air in the lungs.

Slide 79

The Avian Respiratory System

Anterior

air sacs

Posterior

air sacs

Lungs

Air

Lungs

Air

1 mm

Trachea

Air tubes

(parabronchi)

in lung

EXHALATION

Air sacs empty;

Lungs Fill

INHALATION

Air sacs fill

Slide 80

Control of Breathing in Humans

In humans, the main breathing control centers are in two regions of the brain, the medulla oblongata and the pons.

The medulla regulates the rate and depth of breathing in response to pH changes - CO2 levels in the cerebrospinal fluid.

The medulla adjusts breathing rate and depth to match metabolic demands.