9.1 - Respiratory System Flashcards
Conducting Portion
= air passages that lead to the sites of respiration with the lung (where gas exchange takes place)
FXN: conditions the air that is traveling within these passages
Respiratory Portion
= portion of the respiratory tract in which gas exchange takes place
includes:
- respiratory bronchioles
- alveolar ducts
- alveolar sacs
- alveoli
Ciliated Cells
= tall columnar cells with approximately 250 cilia each
FXN: to sweep the mucous coat from the level of the bronchioles to the upper respiratory tract
Mucous Cells
- similar to intestinal goblet cells
- found interspersed among the ciliated cells
morphology: have large mucinogen granules in their cytoplasm
FXN: synthesize and secrete mucous from the nasal cavity to the level of the most distal bronchi
Brush Cells
= columnar shaped cells with blunt microvilli on the apical aspect
- brush cells are often associated with a sensory receptor
FNX: is thus a general sensory role in the respiratory epithelium
Small Granule Cells
- contain secretory granules
- considered to be part of the enteroendocrine cells of the gut + gut derivatives
- can occur singly or in groups
- when found in groups, are often associated with a sensory receptor –> called neuroepithelial cells
Basal Cell
= stem cell that serves as a reserve population that maintains cell replacement of the epithelium from
nasal cavity –> distal bronchi
Mucociliary escalator
= coordinated movement of mucous by the ciliated cells of the respiratory tract
- movement is from distal to proximal
- movement is considered an important protective mechanism in the lung
Bronchus Associated Lymphatic Tissue (BALT)
= cellular region located in the lamina propria of the respiratory tract
- is considered lymphatic tissue
- includes cells: lymphocytes, plasma cells, eosinophils
Trachea
= short, flexible air tube that serves as a conduit for air
- has c-shaped rings that maintain the potency of the airway
- originates at larynx –> extends down neck region to the thorax –> divides into 2 primary bronchi
Bronchus
= air passage that divides into lobar and segmental branches
- conducts air to the distal lung
Morphology: bronchi can be identified by cartilage plates and a layer of smooth muscle
Terminal Bronchioles
= smallest of conducting bronchioles
- lead to the respiratory zone
- lines by ciliated cells + clara cells
- Gas exchange does NOT take place at the level of the terminal bronchiole
Respiratory Bronchioles
= constitute a transitional zone in the respiratory system
- are involved in conducting air and gas exchange
- along the walls contain thin walled out-pocketings = alveoli
Clara Cells
FXN:
- Secrete surface-active agent
- stem cells that maintain bronchiole epithelium
Morphology
= non-ciliated cells
= dome-shaped apical aspect that projects into lumen of the bronchiole
Alveoli
= terminal air spaces of the respiratory system
- stie of gas exchange between air and blood
- each alveolus is surrounded by a capillary network
- surface is lined by Type I and Type II pneumocytes
Type I pneumocytes
= Type I alveolar cells
FXN: gas exchange typically takes place across the type I pneumocyte
Morphology: extremely thin squamous cells joined together by tight junctions
Type II pneumocytes
= Type II alveolar cells
= Septal cells
FXN
- secretory cell responsible for the synthesis and realse of the surface active agent, surfactant
- stem cell for both Type I and Type II pneumocytes
Alveolar Septum
= wall that lies between two neighboring alveoli
- lined by cells and connective tissue
- thin wall surrounding passageways
- very small structure - hard to see even in EM
- Typically divided into thick and thin parts
Thick Part contains:
- fibroblasts, macrophages, eosinophils + ECM
Thinnest part:
- air-blood barrier
Air-Blood Barrier
- found at the thinnest part of the alveolar septum
- consists of (lumen–>blood):
a thin layer of surfactant, type I epithelial cells (pneumocyte), fused basal lamina of the type I pneumocyte and capillary endothelial cell, capillary endothelial cell
Alveolar Macrophages
- Found in both CT and air-space - can migrate across epithelium - mostly crawl along surface of epithelial lumen
- is the resident macrophage of respiratory system
- functions to remove inhaled particles + keep surface of surfactant area clear of debris
EM morphology: see inclusions (more with a smoker)
LM morphology: typically see clear/dark/black material in inclusions
Alveolar pores
= openings in the alveolar septum
- allow for collateral air circulation between alveoli
Pulmonar Circulation
- supplies the capillaries of the alveolar septum and arises from the pulmonary trunk that leaves the RV for the heart
Bronchial Circulation
- Arises from the branches of the aorta
- bronchial arteries provide oxygenated blood to the tissues of the lung including: pleura, CT (except alveolar wall septum), walls of the bronchi and bronchioles
During the 4th week of development body folding gives rise to fore/mid/hindgut. What structures does the foregut region of the gut tube give rise to?
- pharynx
- esophagus
- stomach
- superior duodenum
What day of development does the lung bud appear and from where?
- the foregut (endoderm) gives rise to a ventral evagination –> called the respiratorydiverticulum also known as the lung bud
- this occurs on day 22 of development
True/False. As the lung bud grows into the developing pleural cavities it remains covered by splanchnic mesoderm.
True
Which of the three embryonic layers derives the internal lining (epithelium) of the respiratory system (distal to the pharynx).
- the endoderm
From which embryonic developmental layer (be specific) are the cartilage, muscle, vascular, and CT components derived?
- the splanchnic mesoderm.
What is Hyaline Membrane disease? What is another name for it? What are the effects of the disease?
- occurs due to insufficient surfactant production.
- named for its histological appearance
- equivalent to respiratory distress syndrome
- lack of surfactant prevents normal FXN in developing type I pneumocytes –> they become necrotic and leave their residue along the air-blood interface - further preventing lung FXN
What is Fibrosis?
- CT scarring that occurs due to insults to the lung
- limits the capability of affected alveoli to develop
What is bronchopulmonary dysplasia?
- alternate patterns of fibrosis and alveolar hyperplasia
- evident of a lung that has adapted to focal loss of function
What are the three layers of the wall of the trachea?
1) Muscosa
2) Submucosal Layer
3) Adventitial Layer
Describe the mucosa of the wall of the trachea
- pseudostratified epithelium
- rich elastic lamina propria
Describe the submucosal layer of the wall of the trachea
- contains submucosal glands –> “tracheal seromuscous glands” - also called tracheal submucosal glands
Describe the adventitial layer of the wall of the trachea
- binds trachea to adjacent structures
- has C-shaped cartilage rings
- trachealis muscle spans between the ends of the c-shaped rings
What is the tracheal is muscle
- spans between the ends of the c-shaped rings of cartilage in the trachea
What are the five cell types of the respiratory epithelium? (In the order of most prominent to least prominent)
1) Ciliated Cells - principle cell type
2) Mucous Cells - principle cell type
3) Basal Cells - principle cell type
4) Brush Cells - minor cell type (present in small #s)
5) Small Granule Cells - minor cell type (present in small #s and only viewable with specific stain)
Describe the ciliated cells of the respiratory epithelium
- most numerous type
- extend from the BM–>Lumen
- each has ~250 cilia
- FXN: beat in one direction to push mucous upward
Describe the mucous cells of the respiratory epithelium
- almost as common as ciliated cells
- similar to goblet cells of the intestine
- extend from BM–>Lumen
- mucous typically is washed out in H&E
- work with ciliated cells to move particles from air
Describe the basal cells of the respiratory epithelium
- stem cell of all tracheal epithelium
- short cells
- nuclei: prominent + near level of BM
Describe the Brush cells of the respiratory epithelium
- columnar cells with microvilli
- extend form BM–>Lumen
- basal surface in contact with sensory nerve ending
= also called receptor cells due to their general sensory role
Describe the small granule cells of the respiratory epithelium
- hard to see without a special stain
- have role in lung development
- store hormones in membrane bound granules
- associated with nerve fibers
- may have role in regulating diameter of airway
Surfactant
- reduces surface tension and facilitates the movement of air into cells
- looks like a fuzzy line on airway lumenal side
- made by Type II pneumocyte
Describe the Organization of the alveolar septum (from the airway lumen to blood)
- Surfactant
- Alveolar macrophage
- Alveolar epithelium
- Basement membrane
- CT –> Elastic fibers + smooth muscle + dust cells
- Basement membrane
- Endothelium
Describe the alveolar epithelium
- made up by type I pneumocytes (mostly), which are jointed together by tight JXNs and occluding JXNs
- Also contains type II pneumocytes
- simple squamous epithelum
Describe the elastic fiber component of the CT in the alveolar septum and respiratory system
- surrounds larger blood vessels (pulmonary circulation)
- found at tips of septa - to regulate opening of alveolar sac
- essentially absent in the alveolar septa
Describe the Smooth Muscle component of the CT in the alveolar septum and respiratory system
- Colocalizes with elastin
- will not see it with majority of alveolar septa
Describe the Dust Cell component of the CT in the alveolar septum and respiratory system
- alveolar macrophages accumulate and move to the CT in larger airways when life span is finished
- often will see ingested particles inside them
- they can remain there throughout the life of the person
Describe Type II Pneumocytes
- rounder/less squamous cell than the type I pneumocytes
- tends to sit at the corners of where alveolar septa come together (because it is hardest to have a thin layer there and thus have gas exchange)
- recognizable by intracellular structures called LAMELLAR BODIES - showing surfactant is being produced
Describe the morphology of Type II pneumocytes in EM and LM
EM:
- lamellar bodies with characteristic appearance (lines across them)
- lamellar body extravation produces swirling characteristic appearance
LM:
- see rounder cells with clear dots - representing lamellar bodies
- open nucleus
- look similar to macrophage but use location to recognize them in LM
