11 - Respiratory System Dev and Histo Flashcards
1
Q
Respiratory System: 3 Principle Functions:
A
Air Conduction
Air Filtration
Gas Exchange (respiration)
*Olfaction in nasal cavity
2
Q
Respiratory System: Upper part is associated with
A
development of oral cavity
3
Q
Respiratory System: Lower part developed from
A
lung bud
Thus epithelium has endodermal origin
4
Q
Olfactory Epithelium
A
Pseudostratified columnar epithelium
5
Q
Olfactory Epithelium : Composed of
A
olfactory receptor cells, supporting (sustentacular) cells, basal cells,& brush cells
6
Q
Olfactory Epithelium
Lacks
A
goblet cells
7
Q
Olfactory Epithelium: Olfactory mucosa is found in the
A
nasal mucosa - in a small region of the roof of the nasal cavities.
It is here where there are receptors for sense of smell.
8
Q
Conducting division/zone –
A
nasal cavities, nasopharynx, oropharynx, laryngopharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles
9
Q
Respiratory division/zone
A
– respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli
10
Q
Role of the Conducting Division:
A
Cleans, warms, & humidifies air
11
Q
Role of the Conducting Division: Mucous & serous secretions play a
A
significant role
12
Q
Role of the Conducting Division: Cilia of respiratory epithelium sweep the
A
mucous with the trapped particulate matter toward pharynx
13
Q
Role of the Conducting Division: Air is conditioned as it passes through the
A
conducting portion:
Includes warming, moistening, and removal of particulate materials.
14
Q
Mucous is from
A
goblet cells and mucous secreting glands.
15
Q
Respiratory epithelium (ciliated pseudostratified columnar) along most of the
A
pathway*
16
Q
Histological Characteristics of Conducting Division
A
Cartilage is present (varying forms)** Seromucous glands** Mucous cells** Cilia wherever mucous cells Elastic fibers in CT (except the nose) Exhibit high degree of vascularity
17
Q
Mucosa
Respiratory Epithelium –
A
Ciliated pseudostratified columnar epithelium
18
Q
ciliated columnar cells –
A
tall columnar cells with cilia that project into the overlying mucous
goblet cells
19
Q
basal cells –
A
stem cells from which all other cell types arise
20
Q
Lamina propria –
A
loose connective tissue; contains blood vessels; can contain mucous glands many with serous demilunes
21
Q
Submucosa –
A
connective tissue slightly denser than the connective tissue of the lamina propria; contains blood vessels that may contain many glands
22
Q
Adventitia –
A
composed of connective tissue that binds component to adjacent structures
23
Q
Three parts of the pharynx:
A
Nasopharynx
Oropharynx
Laryngopharynx
24
Q
Nasopharynx
A
Ciliated pseudostratified columnar epithelium
25
Oropharynx
Nonkeratinized stratified squamous epithelium
26
Laryngopharynx
Nonkeratinized stratified squamous epithelium
27
Laryngeal cartilages located in
lamina propria (hyaline & elastic cartilages)
28
Vestibular folds (aka false vocal cords) covered with
respiratory epithelium
| Core contains many mucoserous glands
29
Vocal folds (aka true vocal cords) covered with
nonkeratinized stratified squamous epithelium (along with a large portion of the epiglottis)
Core contains elastic fibers & skeletal muscle
30
Cartilage rings are replaced by
plates or slivers of hyaline cartilage & will disappear
31
Smooth muscle within the walls of will
increase as cartilage decreases
32
Height of the pseudostratified columnar epithelial cells
decreases as the bronchi decrease in diameter
33
Bronchioles
No cartilage in walls
No glands in submucosa
Relatively thick layer of smooth muscle
34
Bronchioles: Epithelium height continues to get
smaller as the bronchioles divide
35
Changes from ciliated pseudostratified columnar epithelium to
Bronchioles
ciliated simple columnar epithelium to ciliated simple cuboidal epithelium
36
Bronchioles: Goblet cells present in the
largest of bronchioles but begin to decrease
37
Bronchioles: Goblet cells not present in the
terminal bronchioles
38
Relatively thick layer of
Bronchioles
smooth muscle
39
Terminal Bronchiole
| Simple cuboidal epithelium interspersed with
non-ciliated cells called Clara cells (also known as club cells)
40
Terminal bronchiole: Small amount of
underlying connective tissue and smooth muscle.
41
Clara Cells: Represent
Represent 80% of the epithelial cell population of the terminal bronchiole
42
Clara Cells: Their function is to
protect the bronchiolar epithelium.
| produce surfactant and other
43
Clara Cells: Apical surface of Clara cells are
dome-shaped and have no cilia
44
Clara Cells: Ciliated cells are present in
small numbers
45
Respiratory Division
From the terminal bronchioles of the conducting system…
Respiratory Bronchioles Alveolar Ducts Alveolar Sacs Alveoli
46
Respiratory Bronchiole: Cuboidal epithelium
| Proximally, both
ciliated cells and Clara cells
| Distally Clara cells predominate
47
Respiratory Bronchiole: Occasionally alveoli may extend from the
lumen of the respiratory bronchiole.
48
Respiratory Bronchiole proximal:
Proximally, both ciliated cells and Clara cells
49
Respiratory bronchiole distal
Distally Clara cells predominate
50
Respiratory Division: Alveolar Ducts
Almost no walls, only alveoli as peripheral boundary
| Rings of smooth muscle are present in the knob-like interalveolar septa
51
Alveoli
150 to 250 million per adult lung
| Interalveolar septa demarcate and separate adjacent alveoli
52
Respiratory Division: Alveolar sacs
Spaces surrounded by clusters of alveoli
| Typically occurs at the termination of the alveolar duct, although may occur along
53
Type I alveolar cells
Squamous cells
Provide minimal diffusion barrier
alveolar surface epithelial cells; squamous cells; lines 95% of alveolar surface.
54
Type II alveolar cells
Type II Alveolar Cells – also called septal cells; cuboidal cells; cover approximately 5% of alveolar surface discharge phospholipid called surfactant which keeps the alveoli from collapsing with each successive exhalation, as it lowers surface tension; these cells do not develop until the end of the 6th month of human embryonic development; alveoli do collapse with each successive exhalation in premature infants whose lungs have not developed sufficiently to produce pulmonary surfactant, causing neonatal respiratory distress syndrome (RDS).
55
Alveolar Macrophages – also known as
dust cells; can be found in the connective tissue of septum and in the air space of alveoli; phagocytize inhaled particulate matter and red blood cells.
56
Endothelial Cells –
compose wall of capillary
57
Fibroblasts –
produce elastic fibers
58
Air-Blood Barrier: composed of
1. Surface lining & cytoplasm of the alveolar cells
2. Fused basal laminae of the alveolar cells & capillary endothelial cells
3. Cytoplasm of the endothelial cells
59
Respiratory diverticulum (lung bud) appears as
Approximately week 4:
outgrowth of foregut
60
Inner lining of larynx, trachea, bronchi, & lungs
Endoderm origin
61
Cartilaginous, muscular, & connective tissue components of
trachea & lungs
| Splanchnic mesoderm
62
Lung bud is initially in
open communication with the foregut
63
As the bud grows caudally, tracheoesophageal ridges begin to
separate the lung bud from the foregut
64
Ridges will fuse to form the
tracheoesophageal septum
Dorsal portion esophagus
Ventral portion trachea & lung buds
65
The respiratory diverticulum maintains
s communication with the pharynx through the laryngeal orifice
66
Abnormalities in partitioning of esophagus & trachea by tracheoesophageal septum result in
esophageal atresia with or without tracheoesophageal fistulas (TEFs)
67
Most frequent abnormality is shown which occurs with the
upper esophagus ending in a blind pouch and the lower segment forming a fistula with the trachea
68
The respiratory diverticulum maintains communication with the pharynx through the
laryngeal orifice
Initially a sagittal slit which changes to a T-shaped opening
69
Laryngeal cartilages and musculature arise from
pharyngeal arch pairs 4 and 6
70
Mesenchyme of the 4th & 6th arch transform into:
Thyroid cartilage
Cricoid cartilage
Arytenoid cartilage
71
Epiglottis forms from
mesenchyme of the caudal hypopharyngeal eminence
72
Laryngeal mm. arising from 4th arch are innervated by
superior laryngeal n.
73
Laryngeal mm. arising from 6th arch are innervated by
recurrent laryngeal n.
74
~ Day 28: Lung bud divides to form
2 primary bronchial buds
75
Day 30:
Right forms 3 secondary bronchial buds
| Left forms 2 secondary bronchial buds
76
Day 38:
Right forms 10 tertiary bronchial buds
| Left forms 8 tertiary bronchial buds
77
This division and formation of the bronchial buds foreshadows the
lobes of each lung and the bronchopulmonary segments of each lung
78
As the lung buds grow in both the caudal & lateral directions, they expand into the
pericardioperitoneal canals which will gradually narrow & form the pleural cavities
79
Splanchnic mesoderm gives rise to
visceral pleura of the lungs
80
Somatic mesoderm lining thoracic body wall gives rise to the
parietal pleura
81
Respiratory tree produces small branches called
terminal bronchioles
82
Between 16-28 weeks, each terminal bronchiole divides into
two or more respiratory bronchioles
83
By approximately week 36,
terminal sacs (primitive alveoli) are formed
84
**Pseudoglandular, canalicular, & terminal sac periods are
fetal stages
85
***The alveolar period is a
late fetal & neonatal stage
86
Lung tissue appears histologically as a collection of
exocrine glands, hence pseudoglandular period
87
Pseudoglandular period: At this time, all the major lung structures have developed except for
most distal portions of respiratory tree where gas exchange occurs
88
A fetus born during Pseudoglandular period will not
survive
89
Canalicular period: Lung tissue becomes
highly vascular
90
Canalicular period:
| At end of this stage,
respiration is possible. Each terminal bronchiole has split into 2 or more respiratory bronchioles, which have developed primitive alveolar ducts. Some ducts already lead into terminal sacs (primitive alveoli)
91
Canalicular period: A fetus born near the end of this stage may
survive, although many die as the lungs are still immature in their development
92
Terminal sac period: More terminal sacs (primitive alveoli) develop and are hugged by
capillaries, establishing the blood-air barrier
93
~ 26 weeks: lining terminal sac walls is a
single layer of simple squamous cells, most of which are type I alveolar cells through which gases diffuse
94
Scattered amongst the type I cells are a few
rounded type II alveolar cells
| Produce, store, and secrete pulmonary surfactant
95
Surfactant forms film over the internal walls of the
alveolar sacs and counteracts surface tension
Facilitates expansion of the terminal sacs by preventing collapse (atelectasis)
-Production begins at 20-22 weeks
96
Premature babies of 24 to 26 weeks may survive, but could suffer from
respiratory distress syndrome due to insufficient surfactant
97
Alveolar period: Alveoli are
fully functional
98
Alveolar period: 95% of mature alveoli develop
postnatally (most form within first 3 years) and will continue to develop until 8 years of age
99
Alveolar period: The alveolar period is a
late fetal & neonatal stage
100
GI tube is
endoderm, thus lung bud is endoderm.
101
Epiglottis between
4th and 3rd pharyngeal pouch
102
olfactory glands in
submucosa - olfactory nerves here as well
103
Clara cells produce
surfactant
