Unit 2A

Human Form & Function

Body systems

The respiratory system

Further information

• Further information about this topic can be found in Our Human Species (3rd edtn)

Chapter 11, sections 1-2, 4-6

Background reading

• Our Human Species (3rd edtn.)

Chapter 11, Gas Exchange

Sections 1, 2, 4, 5, 6, 7

Student work book

Topic 9, Respiratory system

The respiratory system

Structure

Organs of the respiratory system

Larynx

TracheaRib cage

Bronchus

Mediastinum

Lung

Diaphragm

Section through the head

Nasal cavity

Palate

TonguePharynx

Hyoid bone

Epiglottis

Larynx

Esophagus

Teeth

Vocal cords

The Miles Kelly Art library, Wellcome Images

The mucous lining• The nasal cavity and upper airways

have a mucous lining.

• The epithelial lining contains goblet cells which secrete a clear, sticky mucus.

• The function of mucus is to trap dirt particles and microbes before they enter the lungs.

The nose (nasal cavity)• Air enters and leaves the body

through the nose.

• Here it is cleaned, warmed and moistened before entering the body.

• The nasal secretions contain an anti-bacterial enzyme – lysozyme.

A section through the nasal cavity

The Miles Kelly Art library, Wellcome Images

Nostril

Hard palateSoft palate

Sinus

NASAL CAVITY

The larynx (Adam’s apple or voice box)

• The larynx is a box-like structure constructed from nine cartilages and is the entrance to the trachea and lungs.

• The larynx houses the vocal folds or vocal cords.

• The entrance to the larynx is protected by the epiglottis.

Gray’s Anatomy

The bronchial tree

Larynx

Trachea

Bronchus

Bronchiole

The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989)

Trachea & bronchi

• The trachea & bronchi are reinforced with C-shaped rings of cartilage (these prevent the tubes collapsing during inhalation).

The bronchi

The Miles Kelly Art library, Wellcome Images

Mucous lining

Muscular wall

Cartilage rings

• The upper airways are lined with a ciliated mucous membrane–The sticky mucus traps dirt &

microbes–The cilia sweep the dirty mucus

up the trachea and into the throat.

The ciliated lining tissue

Mucus-secreting goblet cells

Cilia

G. Meyer, ANHB-UWA,

EM of ciliated epithelium & goblet cells

D Gregory & D Marshall, Wellcome Images

Alveoli

• The brochioles terminate in microscopic clusters of air sacs – the alveoli.

• Gas exchange takes place in the alveoli.

AlveoliG. Meyer, ANHB-UWA

The alveoli (air sacs)

The Miles Kelly Art library, Wellcome Images

Section through a lung showing alveoli and blood supply

M I Walker, Wellcome Images

The respiratory system

Gas exchange

Exchange surfaces

• Like all exchange surfaces, the alveoli:

–are very thin

–have a large surface area

–are moist

–have a rich blood supply

Breathing

• Breathing (sometimes referred to as ventilation) is the process of moving air into and out of the lungs.

• The purpose of breathing is to exchange oxygen and carbon dioxide between the lungs and the air .

Boyle's law

• Boyle's law states that: for a fixed amount of gas kept at a fixed temperature, pressure (P) and volume (V) are inversely proportional (while one increases, the other decreases).

• This can be stated mathematically as:PV = k

• where: P is the pressure, V is the volume & k is a constant value representative of the pressure and volume of the system.

Respiration

• Respiration is the transport of oxygen from the air to the tissues and the transport of carbon dioxide in the opposite direction.

[not to be confused with the process of cellular respiration discussed earlier]

External respiration and Internal respiration

• External respiration is the movement of O2 and CO2 between the lungs and the bloodstream.

• Internal respiration is the exchange of O2 and CO2 between the blood and the tissues.

External respiration

Partial pressure (mmHg)

Alveolar air Deoxygenated blood

Oxygenated blood

Oxygen 100 40 100

Carbon Dioxide

40 44 40

Breathing maintains the correct concentration of gases in the lungs

Concentration gradient

Breathing – inhaling(remember P1V1 = P2V2)

Anatomical changes

V P1 P1:P2 Result

• Rib cage raised• Diaphragm flattens

Increases Decreases P1<P2 Air drawn into lungs

V = volume of thoracic cavity

P1 = pressure in thoracic cavity

P2 = air pressure

Thoracic volume

Rib cage relaxes Diaphragm domed

Rib cage raised Diaphragm flattens

P1V1 = P2V2

A bicycle pump works in much the same way

as the lungs

The lungs work in much the same way as a bicycle pump

If you increase the volume of the chamber air is sucked in

If you decrease the volume of the chamber air is forced out

Breathing – exhaling(remember P1V1 = P2V2)

Anatomical changes

V P1 P1:P2 Result

• Rib cage relaxes• Diaphragm domed

Decreases Increases P1>P2 Air forced out of lungs

V = volume of thoracic cavity

P1 = pressure in thoracic cavity

P2 = air pressure

The Miles Kelly Art library, Wellcome Images

INHALE EXHALE

Ribcage raised

Ribcage lowered

Diaphragm domed

Diaphragm flattened

Thoracic volume increasedThoracic pressure < air pressure

Thoracic volume decreasedThoracic pressure > air pressure

Why breathe?Fresh air passing through the lungs delivers oxygen to the red blood cells. At the same time, waste carbon dioxide is removed from the blood. This can only occur if fresh air is constantly circulating through the lungs.

Wellcome Photo Library

Carbon dioxide

Oxygen

Oxygen transport

• Oxygen combines with haemoglobin in RBCs to form oxyhaemoglobin.

Carbon dioxide transport• Most CO2 is transported in the plasma as

dissolved bicarbonate ions. -

Oxygen saturation

Diseased lung tissue

Photo by Pöllö

CDC

A. healthy lung tissue

B. Smoker’s lung

C. Emphysema

A

B

C

Study Guide

Read:• Our Human Species

Chapter 11, sections 1-2, 4-6

Complete:• Workbook

Topic 9, Respiratory system