BIOL 121 Chp 23: The Respiratory System

Chapter 23

1

Rob SwatskiAsst. Prof. Biology

HACC – York Campus

The Respiratory System

1

2

The 2 systems that cooperate to supply O2 & eliminate CO2 are the cardiovascular & the respiratory system

Respiratory system provides for gas exchangeCardiovascular system transports the respiratory gases

Failure of either system has the same effect on the body:

- disruption of homeostasis- rapid death of cells: O2 starvation & buildup of

wastes

Introduction

Respiration

The exchange of gases between the atmosphere, blood, & cells

3 basic steps:

1. Ventilation (breathing)

2. External (pulmonary) respiration

3. Internal (tissue) respiration

3

4

Respiratory System Anatomy

Nose

Pharynx = throat

Larynx = voicebox

Trachea = windpipe

Bronchi = airways

Lungs

Locations of infections:

- upper respiratory tract is above vocal cords

- lower respiratory tract is below vocal cords

Conducting system consists of a series of cavities & tubes - nose, pharynx, larynx, trachea, bronchi, bronchiole, & terminal bronchioles - that conduct air into the lungs

Respiratory portion consists of the area where gas exchange occurs - respiratory bronchioles, alveolar ducts, alveolar sacs, & alveoli 5

6

Pharynx

7

Larynx

Cartilage & CT tube

Anterior to C4 to C6

Constructed of 3 single & 3 paired cartilages8

Cartilages of the Larynx

Epiglottis: leaf-shaped piece of elastic cartilage– during swallowing, larynx moves upward– epiglottis bends to cover glottis

Cricoid cartilage: ring of cartilage attached to top of trachea

Pair of arytenoid cartilages sit upon cricoid– many muscles responsible for their movement– partially buried in vocal folds (true vocal cords) 9

Trachea & Bronchial Tree

10

Airway Epithelium

Ciliated pseudostratified columnar epithelium with goblet cells produce a moving mass of mucus

11

Bronchi

The trachea divides into the:

right & left pulmonary bronchi

The bronchial tree consists of the:

trachea, primary bronchi, secondary bronchi, tertiary bronchi, bronchioles, & terminal bronchioles

Bronchi walls: contain rings of cartilage

Bronchiole walls: contain smooth muscle

12

Bronchi & Bronchioles

Primary bronchi supply each lung

Secondary bronchi supply each lobe of the lungs (3 right + 2 left)

Tertiary bronchi supply each bronchopulmonary segment

Repeated branchings called bronchioles form the bronchial tree 13

Branchings of single arteriole, venule & bronchiole are wrapped by elastic CT

Respiratory bronchiole: simple squamous epithelium

Alveolar ducts surrounded by alveolar sacs & alveoli

– sac is 2 or more alveoli sharing a common opening 14

Structures Within a Lobule of Lung

Cells Types of the Alveoli

Type I alveolar cells

– simple squamous cells where gas exchange occurs

Type II alveolar cells (septal cells)

– free surface has microvilli

– secrete alveolar fluid containing surfactant

Alveolar dust cells (macrophages)

– wandering macrophages remove debris

15

16

Details of the

Respiratory Membrane

Pulmonary Ventilation

Respiration occurs in 3 basic steps: pulmonary ventilation, external respiration, & internal respiration

Inspiration (inhalation) is the process of bringing air into the lungs

The movement of air into & out of the lungs depends on pressure changes governed in part by Boyle’s law, which states that the volume of a gas varies inversely with pressure, assuming that temperature is constant

17

As the size of a closed container decreases, the pressure inside increases

The molecules have less wall area to strike so the pressure on each inch of area increases

18

Boyle’s Law

Dimensions of the Chest Cavity

Inhalation requires muscular contraction & chest size changes

Contraction of the diaphragm flattens the dome & increases the vertical dimension of the chest

19

Quiet Inspiration

Diaphragm lowers 1 cm & ribs lifted by muscles

Intrathoracic pressure falls & 2-3 liters inhaled20

Quiet Expiration

Passive process with no muscle action

Elastic recoil & surface tension in alveoli pulls inward

Alveolar pressure increases & air is pushed out21

Labored Breathing

Forced inspiration

– sternocleidomastoid, scalenes & pectoralisminor lift chest upwards as you gasp for air

Forced expiration

– abdominal musclesforce diaphragm up

– internal intercostalsdepress ribs

22

IntrapleuralPressures

Always subatmospheric(756 mm Hg)

As diaphragm contracts intrathoracicpressure decreaseseven more

(754 mm Hg)

Helps keep parietal & visceral pleura sticking together

23

Alveolar pressure decreases & air rushes in

Alveolar pressure increases & air rushes out 24

Summary of Breathing