Lecture 10 Outline
Respiratory System
I.
Overview
1. Ventilation = movement of air into and out of lungs
2. External respiration = gas exchange between lungs and blood
3. Internal respiration = gas exchange between blood and tissues of the body
4. Cellular respiration = cells use O2 for ATP synthesis & produce CO2 as waste
II.
2 Divisions of respiratory system
1. Upper respiratory tract: Includes nose, nasal cavity, sinuses, and pharynx
2. Lower respiratory tract; includes larynx, trachea, bronchial tree, and lungs
Upper Respiratory Tract
III.
Boarders of Nasal Cavity
1. Roof = ethmoid & sphenoid bones
2. Floor = hard & soft palate, and uvula
3. Entrance = nares (external nostrils)
 Contains vestibule; stratified squamous epithelium + hairs = protection
IV.
Sinuses – air filled spaces
1. Frontal, Sphenoid, Ethmoid, Maxillary Sinuses
2. Reduce weight of skull & resonate voice
3. Opens into nasal cavity
V.
Nasal Conchae
1. Superior, Middle, Inferior concha
2. Passage = Meatuses
3. Circulate air & draw air towards olfactory nerves
VI.
Nasal Septum – divides nose
VII.
Histology
1. Nasal cavity is lined with pseudostratified columnar epithelium + goblet cells
2. Vestibule is an exception; stratified squamous epithelium + hairs
VIII.
Functions
1. Removes debris - Mucus traps debris & cilia convey mucus towards pharynx
2. Moistens air – goblet cells secrete mucus that moistens air
3. Warms air – blood vessels radiate heat
4. Smell – houses olfactory nerves
Larynx
I.
Functions
1. Passage for air into trachea
2. Blocks objects from entering lower respiratory tract
3. Speech – houses vocal cords
II.
Cartilages of larynx
1. Thyroid Cartilage “Adam’s Apple” – increases in males during puberty
2. Cricoid cartilage
 Inferior boarder of larynx
 Thicker than thyroid cartilage
3. Epiglottic cartilage
 Only elastic cartilage in larynx
 Attached to upper surface of Thyroid Cartilage
 Covers glottis when swallowing
4. Arytenoid Cartilage
 Pyramid shape
 Attachments for true vocal cords
III.
Vocal Folds (Cords)
1. False Vocal Cords (Vestibular folds)
 Superior to true vocal cords
 Closes glottis when swallowing
2. True Vocal Cords
 Speech
3. Glottis = opening between vocal cords
Trachea “Windpipe”
I.
Overview
a. Location: Anterior to esophagus, passes into mediastinum
b. Structure: about 20 C-shaped rings of hyaline cartilage
II.
Structure
a. Incomplete Hyaline Cartilage rings
 Prevents trachea from collapsing
 Posterior surface covered with smooth muscles – allows esophagus to expand
when swallowing
b. Histology
 Lined with Pseudostratified Columnar Epithelium + Goblet Cells
 Cilia beat upwards to convey debris towards pharynx
c. Tracheostomy
 Incision into trachea to open an obstructed airway
Bronchial Tree
1. Primary Bronchi
 Right Bronchus is shorter & wider than left
2. Secondary Bronchi
 Right Lung = 3, Left Lung = 2
 Left lung is smaller due to heart
3. Tertiary Bronchi
 10 in right lung, 8 in left lung
4. Intralobular Bronchioles
 Enters individual lobules
 Lobule = functional unit of lung
5. Terminal Broncioles
 No cartilage, only smooth muscle
 Site of asthma attacks
6. Respiratory Bronchioles
 Simple cuboidal epithelium replaces ciliated columnar epithelium
 No cilia or goblet cells
7. Alveolar Ducts
8. Alveolar Sacs = groups of alveoli
9. Alveoli
 Simple Squamous Epithelium
 Surface area = half size of tennis court
Alveolar Sacs
1. Alveoli, Type I = Simple Squamous epithelium for gas exchange
2. Alveoli, Type II = secretes surfactant
 Surfactant reduces surface tension of alveoli & prevents them from collapsing
 Respiratory Distress Syndrome = premature newborns produce insufficient surfactant
3. Alveolar Macrophages = phagocytize debris & bacteria, cleans alveoli
4. Elastic Fibers
 Stretch during inspiration
 Passive expiration results from recoil of elastic fibers
 Emphysema = loss of elasticity; difficult to breath out
 Alveoli also collapse
Respiratory Membrane – site of gas exchange
Layers:
1. Surfactant
2. Alveolar epithelium
3. Basement membrane of alveoli
4. Interstitial space
5. Basement membrane of capillary
6. Endothelium of capillary
7. Red blood cell membrane
Lungs
I.
Structure
a. Soft, spongy, cone-shaped organs
b. Right lung = 3 lobes, left lung = 2 lobes + cardiac notch
II.
Pleural Membranes
a. Visceral pleura – adheres to lungs
b. Parietal pleura – lines cavity
c. Pleural cavity
i. potential space between visceral & parietal pleura (no true space)
ii. thin film of serous fluid that reduces friction
Control of Breathing
Respiratory Areas in Medulla Oblongata & Pons
I.
II.
Medullary Respiratory Groups
a. Ventral group
i. Regulates basic rhythm of breathing
b. Dorsal group
i. Responsible for contracting the diaphragm= initiates inspiration
Pontine Respiratory Group
a. Functions unknown
b. Plays a role in switching between inspiration & expiration
c. Not essential for general rhythms