What are the - PowerPoint Presentation

Slide1

What are the mammalian lungs made of?Slide2

Success Criteria

Describe, with the aid of diagrams and photographs, the distribution of cartilage, ciliated epithelium, goblet cells, smooth muscle and elastic fibres in the trachea, bronchi, bronchioles and alveoli of the mammalian gaseous exchange system;

Explain the functions of cartilage, cilia, goblet cells, smooth muscle and elastic fibres in the mammalian gaseous exchange system; Slide3

Starter- Structure of the thorax

Put them in the correct order

Terminal bronchioles

Secondary bronchi

Alveoli, alveolar ducts and alveolar air sacs.

Right and left primary bronchiTertiary bronchiTrachea

Nose Slide4

The structure of the thorax

Nose

Trachea / Windpipe,

Right and left primary bronchi

Secondary bronchi,

Tertiary bronchi

Terminal bronchioles

Alveoli, alveolar ducts and alveolar air sacs.Slide5

Total barrier to diffusion is less than 1 um

O

2

from the atmospheric air entering the alveoli enters the blood by diffusion across the alveolar wall down its concentration gradient

CO

2

from the blood enters the alveoli by diffusion across the alveolar wall down its concentration gradientSlide6

Tissues 1 – the alveoli

Oxygenated blood

to

heart via pulmonary vein

Low CO

2 concentrationDeoxygenated blood fromheart via pulmonary arteryHigh CO2 concentration

Direction of blood flow

Alveoli

–

spherical and numerous (600 million);

100-300

um across – giving a large surface area of approx.80-100 m

2

for rapid gas exchange between the blood and atmosphere; Slide7

RBC’s

– contain haemoglobin - carries

O

2

as

oxyhaemoglobin Plasma – carries CO2 in different formsAlveolus wall

Capillary wall

Each one cell thick

Capillaries are numerous

and tubular

in

close contact with alveoli - wall also made of squamous epithelium and one cell thick; total diffusion distance is less than 1 um

Tissue 2 – capillaries

Capillaries are narrow – red blood cells

squeeze

against the capillary wall – making contact with the wall to reduce diffusion distance. The blood cells are also slowed down – increasing the time for exchangeSlide8

Features of the alveoli

Surfactant

produced by alveoli – reduces cohesive surface tension forces between H

2

O molecules in film of H2O

ST forces may cause collapse of alveoli during exhalation – prevented by surfactantDiffusion gradient maintained by rhythmic ventilation (replaces air in alveoli) and a rich blood supply –Capillaries –standard features of good gas exchange surface Close contact with alveolar wall1 cell thick – short diffusion distanceNarrow – space enough for passage of single RBC – allows close contact with capillary wallLarge surface area – numerous and tubularSlide9

How do these adaptations assist with gas exchange?

Hairs -

Mucus –

Blood in capillaries in nose –

Constant ventilation –

Haemoglobin –Moist surface area –Rich blood supply to alveoli –SurfactantPresence of phagocytes in alveoli -Slide10

Cleans, warms, and moistens the air entering the respiratory

tract–

achieved

by hairs, mucus, and blood capillaries (warm blood) in the nasal cavity

and

cilia in the

trachea

Constant ventilation - replacing the air in the alveoli to maintain a concentration gradient between the alveolar air and the blood

Alveoli are surrounded by a large number of capillaries – a rich blood supply, replaces the blood constantly, to maintain a concentration gradient between the blood and alveolar air.

Haemoglobin (

Hb

) in red blood cells carries oxygen and has a high affinity for oxygen – helps in maintaining a steep concentration gradient for oxygen

Moist exchange surface – allows gases to dissolve

Water in the alveoli contains a surfactant (phospholipid) – reduces surface tension – prevents collapse of alveoli

Alveoli contain phagocytic cells - for defence

Adaptations of Respiratory System for Gas ExchangeSlide11

GAS EXCHANGE

...describe with the aid of diagrams and photographs, the distribution of cartilage, ciliated epithelium, goblet cells, smooth muscle and elastic fibres in the trachea, bronchi, bronchioles and alveoli of the mammalian gaseous exchange system

Rings of cartilage in the walls of the trachea and bronchi provide support

It is strong but flexible

It stops the trachea and bronchi collapsing when pressure dropsSlide12

Structural components of the respiratory system

Trachea

Smooth muscle

Contracts and relax to allow diameter of airways to be controlled.

During exercise the muscle relaxes – making the airways wider – reduces resistance to air flow – aids ventilation

Muscles contracts to narrow the airways when challenged with foreign material (e.g. pollen) to protect airways and alveoli

Elastic fibres

Stretch to allow expansion during inhalation and recoil during exhalation; prevent over expansion

C-shaped rings of cartilage

Provide structural support

Prevent collapse of airway during inhalation

Allows flexibility during movement without narrowing of airways

Allows oesophagus to expand during swallowingSlide13

Compare the role of the smooth muscle and elastic fibres in the trachea (6) Slide14

Smooth muscle is found in the walls of the trachea, bronchi and bronchioles

Smooth muscle relaxes during exercise, widening the lumen

Results in less resistance to airflow

Elastic fibres stretch on inspiration and recoil to help push air out when exhaling

Tissue 3 - Smooth

muscle and elastic fibres in the tracheaSlide15

Structure

Function/Characteristics

Cartilage

Supports trachea and bronchi. Prevents it from collapsing when air pressure is low. Some flexibility to move neck. Allows oesophagus to expand during swallowing.

Tissue 4 – cartilage Slide16

Tissue 5 - Ciliated

epithelium

Simple columnar epithelial cells

Fine hair-like outgrowths

Rapid, rhythmic, wavelike beatings

Movement of mucusUsually found in the air passages like the nose, uterus and fallopian tubesSlide17

Cilia beat the mucus

Helps to prevent lung infections

Ciliated epithelium Slide18

Goblet cells

Specialised as gland cells

Synthesising and secreting mucusSlide19

Secrete mucus

Mucus traps microorganisms and dust particles in inhaled air

Tissue 6- Goblet

cellsSlide20

Structural components of the respiratory system

Inside surface of trachea – epithelial lining

Goblet (mucus) cells

Secrete mucus – traps particles (e.g. dust, pollen, bacteria) – reduce risk of infection & inflammation

Ciliated epithelium

Cilia beat in a synchronised pattern to move (waft) mucus (with particles)

towards throat – to be swallowed (stomach acid kills

bacteria) or expectorated; prevents infection

Cells contain numerous mitochondria (energy for

ciliary

movement)

Loose tissue

Inside surface of cartilage – glandular tissue, connective tissue, elastic fibres, smooth muscle and blood vesselsSlide21

Alveolus wall

Thin - single cell thick

Squamous epithelium

Reduces diffusion distance

Bronchiole wall

Ciliated epithelium (cilia

move mucus upwards)

Goblet cells (secrete

mucus)

Blood capillary

Close to alveoli

Thin - single cell thick

Squamous epithelium

Reduces diffusion distance

Pulmonary vein

Carries oxygenated blood to heart

Cross section of bronchioleSlide22

(a) Bronchiole and (b) trachea in transverse section

(a) Bronchiole and (b) trachea in transverse sectionSlide23

Structure

Function/Characteristics

Cartilage

Smooth muscle

Elastic fibres

Goblet cells and glandular tissue

.

Ciliated epithelium

Bronchi

BronchiolesSlide24

Structure

Function/Characteristics

Cartilage

Supports trachea and bronchi. Prevents it from collapsing when air pressure is low. Some flexibility to move neck. Allows oesophagus to expand during swallowing.

Smooth muscle

Allow contraction and makes lumen of the airway narrower. Restricts harmful substances in the air. Not voluntary and causes asthma.

Elastic fibres

Reduces diameter of the lumen when smooth muscle contracts. Dilates when smooth muscle relaxes, fibres recoil to original shape.

Goblet cells and glandular tissue

Found under the epithelium and secretes mucus to trap tiny particles

e.g

pollen and bacteria. Reduces risk of infection.

Ciliated epithelium

Contains cilia, cells with tiny hairs

Bronchi

Have plates of cartilage in their walls, together with elastic tissue and a mucus-secreting ciliated epithelium.

Bronchioles

No cartilage and the epithelium is simple. No cilia or goblet cellsSlide25

Examples of specialised

exchange surfaces

Small intestine

(absorption of nutrients)

Liver

(Sugar levels adjusted)

Root hair of plants(water and minerals absorbed)

Hyphae of fungi

(nutrients absorbed)Slide26

Practical: Make annotated diagrams of lung tissue

Objectives

To use a light microscope to examine slides of lung tissue

To make annotated diagrams of trachea, alveolar cells and blood vesselsSlide27

(a) Bronchiole and (b) trachea in transverse section

Use the light microscope to make an annotated diagram

of

the trachea/ lung tissue.

Look at the diagrams below.

Draw a table to describe the function and characteristics

for

each part.Slide28

4.

The diagram below shows the detailed structure of a small part of the mammalian lung.

(

i

) State the name of the structure shown between lines

D and E..........................................................................................................................[1]alveolus/alveolar air, sac/space; A alveoli/air sac A squamous epithelium

1

Exam QuestionSlide29

List three

features of the structure which you have identified in (

i

) which make it suitable for gas exchange.

1 ...............................................................................................................................................................................................................................................2 ...............................................................................................................................................................................................................................................

3 ...............................................................................................................................................................................................................................................[3][Total 4 marks] Exam Questionlarge surface area to volume (ratio)/AW; R large area unqualified

thin/one cell thick, wall/short diffusion distance/AW;

A

appropriate figures for width

squamous epithelium;

permeable;

blood supply, qualified;

elastic tissue/recoil (after expansion);

surfactant; 3 maxSlide30

5.

The different parts of the gaseous exchange system, such as the bronchi, show structural adaptations to their functions. The diagram below shows a section through the wall of a bronchus as seen with a light microscope.

Exam QuestionSlide31

(a)(

i

)State

one

function for each of the following components of the bronchus wall.goblet cell ...............................................................................................................................................................................................................cartilage .................................................................................................................................................................................................................

[2] (ii)State two ways in which the structure of the wall of the bronchus would be different in a long-term smoker.1 .............................................................................................................................................................................................................................2 .............................................................................................................................................................................................................................[2] Exam Question

produce / secrete / release, mucus;

prevent collapse of / hold open / support, airways;

A provide shape of bronchus

R gives wall, structure / strength

cilia, destroyed / damaged; R cilia not working

(epithelium replaced by) scar tissue / scarring;

(smooth) muscle becomes thicker;

mucous glands enlarge / larger goblet cells / more goblet cells;

R more mucus secreted

inflammation of connective tissue;

AVP; idea of tumour if it describes a structural changeSlide32

(b) Gaseous exchange occurs across the walls of the alveoli.

Explain why the walls of the alveoli contain elastic fibres.

.........................................................................................................................

.........................................................................................................................

..................................................................................................................................................................................................................................................[2]

Exam Questionstretch, as air is inhaled / allow alveoli to expand during inhalation;to increase lung volume / surface area;

prevents alveoli bursting;(elastic fibres) recoil, as exhale; R contract

more, complete / rapid, expulsion (from the alveoli); A expel more airSlide33

(c) One feature of the disease emphysema is that the alveoli lose their elasticity.

Explain the effects of this loss of elasticity on the gaseous exchange system of a person with emphysema.

.........................................................................................................................

.........................................................................................................................

...........................................................................................................................................................................................................................................................................................................................................................................

...........................................................................................................................................................................................................................................................................................................................................................................[4][Total 10 marks] Exam Questiontidal volume is reduced / less air inhaled and exhaled / residual

volume is larger / air trapped in alveoli / vital capacity smaller;

more difficult to exhale;

(as) alveoli cannot, stretch / recoil;

rapid / shallow, breathing / breathlessness / wheezing;

alveoli may burst;

leaves gaps in tissue / larger air spaces / AW;

less surface area (for gaseous exchange);

blood / haemoglobin, less well oxygenated / less carbon dioxide

removed;

R

less able to do exercise / need to use oxygen

max 4Slide34

The

ribcage,

intercostal muscles

and

diaphragm

all work together to move air into and out of the lungs, where gas exchange occurs across the thin (single-celled) walls of the alveoli

Ventilation is a physical process, relying on the principle of Boyle’s Law – which state

“

Pressure is inversely proportional to volume”

The mechanism can be illustrated using a bell jar model of the respiratory system – however, the model does not illustrate involvement of the rib cage and the intercostal muscles in ventilation

Ventilation

Breathing out

(expiration / exhalation)

Breathing in (inspiration / inhalation)

Internal

intecostals

contract in forced expirationSlide35

Diaphragm & external intercostals contract

Rib cage raised (upwards and outwards)

Diaphragm lowered (becomes flatter)

Volume of chest cavity increases

Pressure in chest cavity drops to below

atmospheric pressure to 758 mmHg

Air moves into lungs from atmosphere

Active process

Diaphragm & external intercostals relax

Rib cage lowered

Diaphragm raised (dome shape) due to push

from abdominal organs

Volume of chest cavity decreases

Pressure in chest cavity increases to

above atmospheric pressure to763 mmHg

Air forced out of lungs into atmosphere

Aided by elastic recoil and abdominal organs Passive process

INSPIRATION

EXPIRATION

Atmospheric pressure = 760 mmHgSlide36
Slide37

Inhaling (Inspiration)

Exhaling (Expiration)

Volume of thorax

Diaphragm muscle

Diaphragm

Relaxes and resumes to dome shape

External intercostal muscles

Rib cage

Pressure in chest cavity

Decreases below atmospheric pressure

Movement of airSlide38

Inhaling (Inspiration)

Exhaling (Expiration)

Volume of thorax

Increases

Decreases

Diaphragm muscle

Contracts

Relaxes

Diaphragm

Flattens and pushes digestive organs down

Relaxes and resumes to dome shape

External intercostal muscles

Contracts/expands

Relaxes

Rib cage

Upward and outward

Inward and downward

Pressure in chest cavity

Decreases below atmospheric pressure

Increases below atmospheric pressure

Movement of air

Into the lungs down pressure gradient

Air forced out of lungsSlide39

Exam question (5 marks)Slide40
Slide41

Exam Questions - OCR

Name five tissues, cells or cell structures found in the mammalian gas exchange system and explain the function of each

[5 marks]Slide42

Name five tissues, cells or cell structures found in the mammalian gas exchange system and explain the function of each

[5 marks]

Goblet cells secrete mucus, the mucus traps bacteria and dust particles

Some cells are ciliated, cilia move mucus towards the throat to be removed

Elastic fibres stretch on inspiration and recoil at expiration

Smooth muscle relaxes to make air passages wider when exercisingCartilage provides support and keeps trachea open