The Respiratory System

• Cells continually use O2

& release CO2

• Respiratory system

designed for gas

exchange

• Cardiovascular system

transports gases in blood

• Failure of either system

– rapid cell death from O2

starvation

23-2

Human Lungs

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

External Nasal Structures

• Skin, nasal bones, & cartilage lined with mucous membrane

• Openings called external nares or nostrils

Nose -- Internal Structures

• Large chamber within the skull

• Roof is made up of ethmoid and floor is hard palate

• Internal nares are openings to pharynx

• Nasal septum is composed of bone & cartilage

• Bony swelling or conchae on lateral walls

Functions of the Nasal Structures

• Olfactory epithelium for sense of smell

• Pseudostratified ciliated columnar with goblet

cells lines nasal cavity

– warms air due to high vascularity

– mucous moistens air & traps dust

– cilia move mucous towards pharynx

• Paranasal sinuses open into nasal cavity

– found in ethmoid, sphenoid, frontal & maxillary

– lighten skull & resonate voice

Pharynx

• Muscular tube (5 inch long) hanging from skull

– skeletal muscle & mucous membrane

• Extends from internal nares to cricoid cartilage

• Functions

– passageway for food and air

– resonating chamber for speech production

– tonsil (lymphatic tissue) in the walls protects

entryway into body

• Distinct regions -- nasopharynx, oropharynx and

laryngopharynx

Regions of Pharynx

Nasopharynx: passageway for air only

Oropharynx and Laryngopharnx: passageway for food & air

Cartilages of the Larynx

• Thyroid cartilage forms Adam’s apple

• 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)

Larynx

• Cartilage & connective tissue tube

• Anterior to C4 to C6

• Constructed of 3 single & 3 paired cartilages

Anterior Posterior

Vocal Cords

• False vocal cords (ventricular folds) found above

vocal folds (true vocal cords)

• True vocal cords attach to arytenoid cartilages

Trachea

• Size is 5 in long & 1in diameter

• Extends from larynx to T5 anterior to the esophagus and then splits into bronchi

• Layers

– mucosa = pseudostratified columnar with cilia & goblet

– submucosa = loose connective tissue & seromucous glands

– hyaline cartilage = 16 to 20 incomplete rings

• open side facing esophagus contains trachealis m. (smooth)

• internal ridge on last ring called carina (cough reflex)

– adventitia binds it to other organs

23-13

Histology of the Trachea

• Ciliated pseudostratified columnar epithelium

• Hyaline cartilage as C-shaped structure closed by

trachealis muscle

Trachea and Bronchial Tree

Airway Epithelium

• Ciliated pseudostratified columnar epithelium with goblet

cells produce a moving mass of mucus.

Bronchi and 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 a bronchial tree

Histology of Bronchial Tree

• Epithelium changes from pseudostratified ciliated columnar to nonciliated simple cuboidal, and finally to simple squamous as pass deeper into lungs

• Incomplete rings of cartilage replaced by rings of smooth muscle & then connective tissue

– sympathetic NS & adrenal gland release epinephrine that relaxes smooth muscle & dilates airways

– asthma attack or allergic reactions constrict distal bronchiole smooth muscle

Pleural Membranes & Pleural Cavity

• Visceral pleura covers lungs --- parietal pleura lines

ribcage & covers upper surface of diaphragm

• Pleural cavity is potential space between ribs & lungs

Gross Anatomy of Lungs

• Base, apex, cardiac notch

• Oblique & horizontal fissure in right lung results in 3 lobes

• Oblique fissure only in left lung produces 2 lobes

Mediastinal Surface of Lungs

• Blood vessels & airways enter lungs at hilus

• Covered with pleura (parietal becomes visceral)

23-21Lobules

Structures within a Lobule of Lung

• Branchings of single

arteriole, venule &

bronchiole are wrapped by

elastic CT

• Respiratory bronchiole

– simple squamous

• Alveolar ducts surrounded

by alveolar sacs & alveoli

– sac is 2 or more alveoli

sharing a common opening

Photomicrograph of

lung tissue showing

bronchioles, alveoli

and alveolar ducts.

Histology of Lung Tissue

Cells Types of the Alveoli

• Type I alveolar cells

– simple squamous cells where gas exchange occurs

• Type II alveolar cells

– free surface has microvilli

– secrete alveolar fluid containing surfactant

• Alveolar dust cells

– wandering macrophages remove debris

Alveolar-Capillary Membrane

• Respiratory membrane = 1/2 micron thick

• Exchange of gas from alveoli to blood

• 4 Layers of membrane to cross

– alveolar epithelial wall of type I cells

– alveolar epithelial basement membrane

– capillary basement membrane

– endothelial cells of capillary

• Vast surface area = handball court

Details of Respiratory Membrane