Ch.2 Anatomy of Respiration

Respiration

Gas exchange between an organism and its environment

Inspiration

Inhaling oxygen

Expiration

Removing CO₂

Purposes of respiration

Biological and speech

Gas exchange occurs in ____ within the ____

alveoli, pulmonary apparatus

Inspiration is

an active, muscular process

Expiration is

passive or active depending on the context (quiet vs. forced)

Boyle’s Law

Pressure and volume are inversely related

Mechanics of inspiration

Increase thoracic volume → pressure drops → air flows in

Mechanics of expiration

Decrease volume → pressure rises → air flows out

Goal of inspiration

Brings oxygen into the lungs

Goal of expiration

Eliminates carbon dioxide from the body

Stucture of the pulmonary apparatus

lungs, trachea, bronchi, alveoli

Purpose of Pulmonary Apparatus

Structures that perform gas exchange

Purpose of Respiratory System

The functional system supporting gas exchange

If lungs are passive structures, what moves them?

Muscles

INSPIRATION – the active process

Inspiration is active: requires muscular contraction.

Primary muscle: Diaphragm.

Expands thoracic cavity, reduces internal pressure.

Air flows in to equalize pressure.

What is the primary muscle of inspiration?

Diaphragm

EXPIRATION – passive and active

Quiet expiration: passive (recoil of lungs and rib cage).

Forced expiration: active, requires abdominal and thoracic muscles.

Air pressure increases → air pushed out.

Quiet expiration

passive (recoil of lungs and rib cage)

Forced expiration

active, requires abdominal and thoracic muscles.

Formula for air pressure

Air pressure = Force / Area

AIR PRESSURE and VOLUME

↑ Volume = ↓ Pressure → air in

↓ Volume = ↑ Pressure → air out

Bony thorax

vertebrae, ribs, sternum

Visceral thorax

lungs, airways, blood vessels

Muscles

diaphragm, intercostals, accessory muscles

Structures of respiration are sorted into what subsystems?

supportive, functional, and muscular

Structures of respiration

Rib Cage and Vertebrae (Bony Thorax)

BONY THORAX – Rib Cage and Vertebrae

12 pairs of ribs, connected to thoracic vertebrae

Ribs move up and out during inspiration

Ribs 1–7: true ribs, 8–10: false ribs, 11–12: floating ribs

Provides protection and mechanical leverage.

True ribs

1-7

False ribs

8-10

Floating ribs

11-12

How many pairs of ribs do we have?

12

Vetebral column

5 Regions of the vetebral column

Cervical (7), Thoracic (12), Lumbar (5), Sacral (5 fused), Coccygeal (4 fused)

Vetebral Column

Supports body weight and anchors ribs.

Provides attachment points for respiratory muscles.

Cervical vertebrae

C1-C7

Thoracic vertebrae

T1-T12

Lumbar vertebrae

L1-L5

THE STERNUM aka “breastbone”

 Central anterior attachment point for ribs.

 Three parts: manubrium, body, xiphoid process.

 Provides attachment for muscles (e.g., sternocleidomastoid).

What are the 3 parts of the sternum?

manubrium, body, xiphoid process

Which part of the sternum provides attachment for muscles?

Sternocleidomastoid

Sternum

THE RIB CAGE and COSTAL CARTILAGE

Flexible and mobile, allowing expansion and recoil.

Cartilage permits rib movement without breaking.

Protects thoracic organs while supporting breathing.

Rib cage and costal cartilage

Costal cartilage structure

Hyaline cartilage connecting ribs to sternum

Trachea and broncial tree

Flexible, cartilaginous tube ~11 cm long

Bifurcates into right and leftmainstem bronchi

Bronchi divide into secondary and tertiary branches

Lined with cilia for filtering debris

LUNGS and LUNG LOBES

Right lung: 3 lobes; left lung: 2 lobes (to accommodate heart)

Made of spongy, elastic tissue—passive in movement

Surrounded by pleural membranes to reduce friction

Contain alveoli where gas exchange occurs

Which lung only has two lobes?

Left

ALVEOLI and GAS EXCHANGE

~300 million alveoli per lung

Surrounded by capillary networks for O₂ and CO₂ exchange

Extremely thin walls to allow diffusion

Site of respiration at the cellular level

Pleural Linings

Visceral pleura, Parietal pleura, Pleural fluid

Prevents lung collapse and supports smooth movement

Visceral pleura

covers the lungs

Parietal pleura

lines the inside of the thoracic cavity

Pleural fluid

reduces friction, creates surface tension

Pleural lining

Pulmonary System Main Concepts

Trachea → Bronchi → Bronchioles → Alveoli.

Lungs are passive but highly elastic.

Gas exchange = primary respiratory function.

Pleural system ensures smooth, stable expansion.

Diaphragm

Function: Expands thoracic cavity vertically; primary muscle of inspiration.

Dome-shaped, unpairedmuscle separating thorax and abdomen

Origin: xiphoid process

Course: upward and medially

Insertion: central tendon

Contraction → flattens diaphragm, increases thoracic volume

External intercostals

Located between ribs; run downward and forward

Elevate ribs during inspiration.

Increase anterior-posterior and transverse thoracic dimensions.

Active during quiet and forced inspiration.

External intercostals OCIF

Origin: Inferior surface of ribs 1–11.

Course: Downward and forward.

Insertion: Superior surface of the rib below.

Function: Elevate ribs; expand thoracic cavity in inspiration.

Accessory Muscles of Inspiration - Overview

Used during deep or forceful inspiration (e.g., speech, exercise).

Include: sternocleidomastoid, scalenes, pectoralis major/minor, serratus anterior, levator scapulae.

Elevate ribs, sternum, or stabilize the upper thorax

Sternocleidomastoid

Elevates sternum and clavicle. 2 heads, clavicular and sternal

Scalenes (anterior, middle, posterior)

elevate ribs 1 and 2.

Sternocleidomastoid and Scalenes Function

Provide vertical lift for upper rib cage

Active in speech breathing and respiratory distress

Sternocleidomastoid OCIF

Origin: Mastoid process of temporal bone

Course: Downward

Insertion: Manubrium of sternum and clavicle

Function: Elevates sternum andclavicle; expands upper thorax during inspiration

Scalenes OCIF

Origin: Transverse processes of cervical vertebrae C2–C7.

Course: Downward.

Insertion: Ribs 1 and 2.

Function: Elevate first and second ribs; stabilize upper thorax during inspiration.

What do the pectoralis major and minor do?

Assist in expanding thoracic cavity superiorly and anteriorly

Important in postural compensation during respiration

Pectoralis major

elevates sternum and rib cage (with fixed arm)

Pectoralis minor

lifts ribs 3–5

Pectoralis Major OCIF

Origin: Clavicle, sternum, and costal cartilages of ribs 1–6

Course: Laterally and upward

Insertion: Humerus

Function: Elevates sternum; expands rib cage during forced inspiration when arm is fixed

Pectoralis minor OCIF

Origin: Anterior surfaces of ribs 2–5

Course: Upward and laterally

Insertion: Coracoid process of scapula

Function: Elevates ribs 2–5 during deep inspiration when scapula is fixed

Additional acessory muscles of inspiration

Serratus anterior, Levator scapulae,Trapezius

Contribute during deep inspiration or compromised breathing.

Serratus anterior OCIF

Origin: Outer surfaces of ribs 1–9.

Course: Around the thoracic wall, posteriorly.

Insertion: Inner border of the scapula.

Function: Elevates ribs and stabilizes scapula during forced inspiration.

Levator scapulae OCIF

Origin: Transverse processes of C1–C4

Course: Downward and laterally

Insertion: Medial border of scapula

Function: Elevates scapula; stabilizes shoulder girdle during respiration

Trapezius OCIF

Origin: Spinous processes of C7–T12

Course: Fan laterally

Insertion: Clavicle and scapula

Function: Stabilizes and elevates shoulder girdle; assists indirectly in expanding thoracic cavity

Muscles of forced expiration - Overview

Expiration is passive at rest, but active during speech or exertion.

Forced expiration uses abdominal and thoracic muscles.

Compress thoracic cavity → push air out forcefully

Internal Intercostals

Located between ribs; run downward and backward.

Pull ribs down and inward.

Decrease thoracic volume → push air out.

Active in forced expiration

Internal Intercostals OCIF

Origin: Superior margin of ribs 1–11

Course: Upward and medially

Insertion: Inferior surface of the rib above

Function: Depress ribs during forced expiration

Iliac Crest

Location: Superior border of the ilium (largest bone in the pelvis).

Landmark: Easily palpable on both sides of the lower torso.

Attachments: Serves as an anchor for abdominal and back muscles (e.g., external/internal obliques, transversus abdominis, latissimus dorsi).

Function: Provides structural support and muscle leverage during posture, trunk movement, and respiration.

Iliac Crest

ABDOMINAL MUSCLES in EXPIRATION

Major players: rectus abdominis, transversus abdominis, internal and external obliques

Compress abdominal contents → push diaphragm upward

Provide force for controlled, sustained exhalation

Rectus Abdominis OCIF

Origin: Pubic symphysis and pubic crest

Course: Vertically upward

Insertion: Xiphoid process and costal cartilages of ribs 5–7

Function: Compresses abdominal contents; pulls sternum downward during forced expiration

External Oblique OCIF

Origin: Outer surfaces of ribs 5–12

Course: Downward and medially (“hands in pockets”)

Insertion: Iliac crest, inguinal ligament, and abdominal aponeurosis

Function: Compresses abdomen; flexes and rotates trunk; supports forced expiration

Internal Oblique OCIF

Origin: Inguinal ligament, iliac crest, and thoracolumbar fascia.

Course: Upward and medially.

Insertion: Lower ribs (10–12) and abdominal aponeurosis.

Function: Compresses abdomen; rotates and flexes trunk; assists in forced expiration

Transverse abdominis OCIF

Origin: Inguinal ligament, iliac crest, lower six ribs, thoracolumbar fascia.

Course: Horizontally across abdomen.

Insertion: Abdominal aponeurosis and linea alba.

Function: Deepest abdominal layer; compresses abdominal cavity; supports forced expiration and posture

Primary muscles of inspiration

diaphragm + external intercostals (primary), accessory muscles when needed.

Primary muscles of forced expiration

internal intercostals + abdominal muscles

Breathing for speech is not the same as breathing at rest

True

Bitch

We’re done