Lecture 13: The Respiratory System Flashcards
What are the 2 functional components of the respiratory system.
- Conducting portion: conditions the air and brings it to the lungs
- Respiratory portion: Site of gas exchangevbetween blood and air.
What is the conducting portion composed of?
Includes parts which are outside the lung or extrapulmonary
And parts which are inside the lung or intrapulmonary
What 5 structures compose the conducting portion?
Nasal cavities, pharynx,
larynx, trachea and primary bronchi
What structures is the intrapulmonary portion composed of?
- Secondary and successive bronchi
- Bronchioles and terminal bronchioles
- Alveolar ducts and sacs, and alveoli
Define the nasal cavity
The nasal cavities are paired chambers separated by a bony and cartilaginous septum.
Through which structure does the nasal cavity contact the outside world?
Each cavity or chamber communicates anteriorly with the external environment through the anterior nares (nostrils)
Through what structure does the nasal cavity communicate posteriorly?
The choanae.
What is the lateral border of the nasal sinuses?
Paranasal sinuses and nasolacrimal duct
What are the 3 sections of the nasal cavity
- Nasal vetibule
- Resiratory Region
- Olfactory Region
What is the nasal vetibule? What type of tissue is it composed of?
A dilated space of the nasal cavity just inside the nostrils and is lined by skin
Composed of keratinized stratified squamous epithelium
What is the respiratory region of the nasal cavity, and what tissues is it composed of?
Is the largest part (inferior two-thirds) of the nasal cavities and is lined by respiratory mucosa
Respiratory mucosa contains a ciliated, pseudostratified columnar epithelium
What are the 5 cell types of the respiratory epithelium?
- Ciliated cells
- Goblet cells
- Brush cells
- Small granule cells
- Basal cells
What is the structure and function of the ciliated cells?
tall columnar cells with cilia that project into the mucus covering the surface of the epithelium.
Cilia (C) move mucous out of the respiratory system
Function of the Goblet cells?
Secretes mucus
Structure and function of Brush cells in respiratory epithelium
Have short, blunt microvilli
Chemosensory cells
Small granule cells?
resemble basal cells but contain secretory granules. These are endocrine cells of the diffuse neuroendocrine system
Basal cells?
stem cells from which the other cell types arise.
Function of the lamina propria of respiratory tract? Glands?
Contains complex vasculature w/ loops of capillaries
Carries blood counter to flow of air and releases heart to warm incoming air
Seromucous glands secrete water to humdify air
Function of mucous layer secreted by seromucous glands and goblet cells?
What Ig is present in mucous?
Immune role - trap particulate and gaseous air impurities that are then removed. The secretions also contain immunoglobulin A (IgA) from plasma cells in the lamina propria
Identify the areas indicated with arrows and dotted line. What cell type are the colorless cells in membrane?
Dotted line = lamina propria
Top arrow = ciliated cells
Bottom arrow = Basement membrane
Colorless cells = goblet cells
Identify goblet cells, ciliated cells, basement membrane and lamina propria
G=goblet
C = ciliated
BM = basement membrane
LP = lamina propria
Identify indicated structures
What part of the nasal cavity comprises the olfactory region? What type of tissue? How is this tissue identified?
located at the apex (upper one-third) of each nasal cavity and is lined by specialized olfactory mucosa
distinguished by its slight yellowish brown color caused by pigment in the olfactory epithelium and the associated olfactory glands
What structure do cells of the olfactory epithelium possess? What three cells types are present?
Pseudostratified, but different three major cell types:
1. Olfactory receptor cells
2. Supporting cells
3. Basal Cells
Describe structure and fuction of olfactory receptor cells
- Bipolar olfactory neurons that span the thickness of epithelium
- Enter the central nervous system
- Respond to odoriferous substances by generating action potentials
How do olfactory receptors leave epithelium and enter CNS?
- unmyelinated axons leave the epithelium and unite in the lamina propria as very small nerves
- Then to the brain through foramina in the cribriform plate of the ethmoid bone.
- There they form the olfactory nerve (cranial nerve I) and eventually synapse with neurons in the olfactory bulb of the brain.
Describe the structure and function of supporting or sustentacular cells in olfactory portion of the nasal cavity. What do they secrete?
- Columnar cells similar to neuroglia
- Provide mechanical and metabolic support to olfactory receptor cells
- Synthesize and secrete odor-binding proteins
What are the basal cells?
Stem cells from which new olfactory receptor cells and supporting cells differentiate.
Describe lamina propria of olfactory epithelium. Types of vessels they contain, nerves and glands.
directly contiguous with the periosteum of the underlying bone
Connective tissue that contains numerous blood and lymphatic vessels
Contains unmyelinated olfactory nerves, myelinated nerves, and olfactory glands
Identify the indicated structures
Identify the indicated structures of the olfactory epithelium
Identify tissue type, and the indicated structures.
Where are the olfactory (Bowman’s) glands found and what is their function?
- They are found in the lamina propria that underlines the olfactory epithelium
- Secrete fluid around olfactory cilia
- Aid in trapping odoriferous substances
Familiarize yourself with the following
What are the paranasal sinuses? What type of tissue is it composed of? What gives them their names?
- Air-filled spaces in the bones of the walls of nasal cavity.
- Extensions of the respiratory region of the nasal cavity
- Lined with thin, ciliated, pseudostratified columnar epithelium with numerous goblet cells
- Named by bones they are found in (ethmoid, frontal, sphenoid and maxillary)
What type of tissue is found in the pharynx and larynx?
ciliated pseudostratified columnar epithelium except in areas subject to abrasion (oropharynx, laryngopharynx and epiglottis)
scattered lymphatic tissue is frequently present, and sometimes aggregates in a larger mass, forming a tonsil
Describe the structure and function of trachea.
- The trachea is a short, flexible, air tube about 2.5 cm in diameter and about 10 cm long
- Conduit for inspired air; assists in conditioning inspired air
- extends from the larynx to about the middle of the thorax, where it divides into the
two main (primary) bronchi
What keeps the lumen of the trachea open?
The cartilaginous rings
What are the 4 definable layers of the trachea’s wall?
- Mucosa
- Submucosa
- Cartilaginous layer
- Adventitia
Trachea: Where is the mucosa and what cell type? What 2 layers is it composed of?
- Composed of a ciliated, pseudostratified epithelium and an elastic, fiber-rich lamina propria.
- Located beneath the tracheal epithelium is a distinctive layer typically referred to as a basement membrane. (light pink area beneath the lamina propria
Which part of the tracheal wall is considerably thicker in smokers?
Basement membrane
Describe basement membrane in people with asthma
the basement membrane is also thicker and more pronounced, especially at the level
of the bronchioles is people with asthma
Tracheal Lamina Propria:
1. Tissue type
2. Types of cells
3. Additional tissue type
- Loose connective tissue
- Very cellular: lymphocytes, plasma cells, mast cells, eosinophils and fibroblasts
- Lymphatic tissue
Tracheal Lamina Propria:
1. Tissue type
2. Types of cells
3. Additional tissue type
- Loose connective tissue
- Very cellular: lymphocytes, plasma cells, mast cells, eosinophils and fribroblasts
- Lymphatic tissue
Tracheal Submucosa:
1. Tissue type
2. Lymphatic tissue
3. Vessels
4. Types of glands?
- Slightly denser connective tissue than lamina propria
- Diffuse lymphatic tissue and nodules extend here from lamina propria
- Larger distributing vessels and lymphatics of tracheal wall
- Mucosal glands of mucus-secreting acini
Tracheal Cartilaginous Layer:
1. Types and number of cartilaginous rings
2. What does cartilage arrangement allow
3. What happens with age
- C-shaped hyaline cartilages, which number about 16 to 20
- arrangement provides flexibility to the tracheal pipe and also maintains patency of the lumen
- With age, the hyaline cartilage may be partially replaced by bone tissue causing it to lose much of its flexibility
From where does this tissue type come from? Name the layers.
Trachea. Dont forget basement membrane below LP (not labeled)
Describe the structure and location of tracheal adventitia.
composed of connective tissue that lies peripheral to the cartilage rings and trachealis muscle, represents the outer layer of the tracheal wall
Which layer of the trachea contains the largest blood vessels and nerves that supply the tracheal wall?
Adventitia
Identify each layer of the tracheal wall.
Primary Bronchi:
1. Mucosa
2. Rings
3. Glands
4. Muscle
- Mucosa similar to trachea except for the catilage and smooth muscle
- Most cartilage rings completely encircle the lumen, but is replaced with smaller isolated plates at smaller diameters
- Mucous and serous glands
- Crisscrossing bundles of smoother muscle and elastic fibers (more prominent in smaller branches)
What type of tissue is this? Identify the lettered areas.
Primary bronchi
Type of tissue? Name lettered sections.
Bronchial wall
Describe divisions of bronchial tree following the primary bronchi
- primary bronchi course downward and outward, giving rise to secondary (lobar) bronchi
- three in the right and two in the left lung
- each supplies a pulmonary lobe
- These lobar bronchi again divide, forming tertiary (segmental) bronchi.
- Conducting bronchiole
- Terminal bronchioles
- Respiratory bronchioles
- Alveolar ducts
- Alveolar sacs
Describe structure of secondary and successive bronchi
similar to the trachea and primary bronchi – mucosa, smooth muscle and cartilage layer, and adventitia. There is an additional layer of smooth muscle
Smooth muscles separtes lamina propria on lumenal side, from submucosa which is closer to cartilage
Smooth muscle is considered part of the lamina propria
Bronchioles:
* Lumen diameter
* epithelium
* muscle
* cartilage
* goblet cells
- Lumen = 1mm or less
- Epithelium is simple columnar with cilia
- Smooth muscle
- No cartilage - Fibrous connective tissue
- No goblet cells - Avoid mucous clogging up smaller passageways
Tissue type?
Bronchioles
Terminal Bronchioles:
* Epithelium
* muscle
* cartilage
* types of cells
- simple cuboidal with cilia
- smooth muscle
- no cartilage
- no goblet cells
- club cells, formerly Clara cells
Function of Club cells?
contain secretory granules:
they secrete components of
the surfactant
What components form the respiratory portion of the respiratory system?
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli
What part of the bronchial tree first allows gas exchange?
Respiratory bronchioles
They constitute a transitional zone in the respiratory system
Involved in conduction and gas exchange
What type of epithelium lines respiratory bronchioles?
What types of cells are present at the more proximal, and distal portions?
Cuboidal epithelium.
Epithelium contains Club cells and transitions from ciliated to non-ciliated cuboidal epithelium in the distal segments
Club cells predominant distally.
Distal ends branch to tubes (alveolar ducts) that are lined by openings of alveoli
What are alveolar ducts? What tissue do they contain?
Distal ends of respiratory bronchioles branch into tubes called alveolar ducts, which are completely lined by the openings of alveoli.
Both the alveolar ducts and the alveoli themselves are lined with extremely attenuated squamous cells.
What are alveolar sacs?
Properties of alveolar lamina propria?
What surrounds each alveolus?
Larger clusters of alveoli called alveolar sacs form the ends of alveolar ducts distally and occur
occasionally along their length
Thin lamina propria, consisting of web of elastic and reticular fibers encircling alveolus
Network of capillaries also surrounds each alveolus
What are alveoli?
The alveoli are the terminal air spaces of the respiratory system and are the actual sites of gas exchange between the air and the blood
Small sacs, open on one side to allow air to enter
Surrounded bt network of capillaries
What are the 4 cell types present in alveoli?
Type I alveolar cells - type I pneumocytes
Type II alveolar cells - type II pneumocytes or septal cells
Brush cells
Dust Cells
Identify indicated structures
Type I Alveolar cells:
1. What percentage of entire alveolar lining cells?
2. Tissue type
3. Percentage of surface
4. What joins cells together
5. Are they capable of cell division
- 40% of entire alveolar lining cells
- Extremely thin squamous cells
- Line 95% of surface of alveoli
- Joined to one another by occluding junctions
- Not capable of cell division
Alveolar Type II cells:
1. Percent of lining and air surface
2. What are lamellar bodies
3. What are they progenitor cells for?
- Type II cells account for 60% of the alveolar lining cells, but because of their different shape, they cover only about 5% of the alveolar air surface
- Graunules rich in a mixture of phospholipids, neutral lipids, and proteins that is secreted by exocytosis to form surfactant.
- progenitor cells for type I alveolar cells - after injury they proliferate and restore both types of alveolar cells
What is an important marker of alveolar injury and repair of alveoli?
Hyperplasia of type II alveolar cells
Function of brush cells in alveoli?
Brush cells are also present in the alveolar wall, but they are few in number. They may serve as receptors that monitor air quality in the lung
What forms surfactant in alveolar type II cells, and where is it stored?
Processed in rough endoplasmic reticulum and stored in lamellar bodies
Familiarize self w/ different cell types
- Type I alveolar cell (I) (darker)
- Type II alveolar cell (II) (lighter)
- Macrophages or dust cells (M)
- Capillary cells (C)
What separates neighboring alveoli and extracellular matrix (ECM) of elastic and reticular fibers?
Intralveolar Septa
Characteristics of Interalveolar septum:
1. Vasculature
2. What separates air from blood
3. What connects neighboring alveoli that open to different bronchioles
- Highly vascularized
- Blood-air barrier or respiratory membrane
- Alveolar Pores
Describe the structure and function of the blood-air barrier
- Gas exchange between alveoli and capillaries
- Physical barrier for cells but O2/CO2 can diffuse through
3 components of the blood air barrier
3 components:
* Thin layer of surfactant
* Type I alveolar cell and its basal lamina
* Capillary endothelial cell and its basal lamina
Identify indicated areas of the blood-air barrier
What are alveolar dust cells?
Macrophages derived from blood monocytes.
They scavenge the surface of air spaces to remove inhaled particulate matter (dust / pollen)
-also phagocytize RBCs that enter alveoli in heart failure
- destroy infectious organisms
What is an important function of alveolar pores?
Equalize air pressure and permits collateral circulation of air if bronchiole becomes obstructed
