Lungs- Microscopic anatomy

Question 1

Why do we get smokers lung?

Answer 1

Lungs do not have the ability to get rid of harmful substances and it accumulates

Question 2

Divisions of the respiratory system

Answer 2

1. Respiratory passages- nasal region to terminal bronchioles in the lungs
2. Olfactory region- detects smelly stuff
3. Gas-exchange region- respiratory bronchioles to alveoli (tissues back to lungs)

Question 3

Nasal cavity components

Answer 3

• Concha- (dorsal, ethmoidal and ventral)- bony plates that create pathways, increase surface area for air flow. Mucous membrane over the area can help with moistening air, warming it up, and capturing harmful materials
• Meatus- (dorsal, middle, common, ventral)- air spaces

Question 4

Cells of respiratory epithelium

Answer 4

1. Ciliated cells- for movement
2. Goblet cells- secreting cells (water or mucous)
3. Basal cells- give rise to other cells and provide attachment to cells above it
4. Neuroendocrine cells- have hormone secreting ability
5. Brush cells- have microvilli. Somewhat unknown function but may be associated with chemoreceptor function/ air quality monitoring because they are associated with nerve endings

Question 5

What is the respiratory epithelium?

Answer 5

Ciliated Pseudostratified columnar

Question 6

Blood vessels of respiratory epithelium

Answer 6

• Many blood vessels present.
• When congested, these blood vessels along with mucous are expanded and blocking pathways. Cilia lining the pathways will be moving and pushing mucous outwards

Question 7

Parts of the airway

Answer 7

1. Glottis- ventilation, phonation, airway protection to help keep trachea open
2. Laryngeal vestibule- extends to the vocal cords
3. Infraglottic cavity
4. Trachea – air from larynx to lungs

Question 8

Trachea

Answer 8

Musculo-cartilaginous tubular airway that connects larynx with bronchi

Question 9

Layers of trachea

Answer 9

• Tunica mucosa
• Propria submucosa
• Tunica muscularis
• Tunica adventitia/serosa

Question 10

What supports the trachea wall?

Answer 10

C-shaped hyaline cartilage tings that open dorsally

Question 11

Tunica mucosa- trachea

Answer 11

• Lined by respiratory epithelium with mucus secreting goblet cells
• Epithelium contains basal, ciliated, secretory, and brush cells
• Few clara cells and neuroendocrine cells

Question 12

Propria submucosa-trachea

Answer 12

• Consists of loose connective tissue rich in elastic fibers, fibrocytes, plasma cells, mast cells and leucocytes
• Contains seromucous glands that are abundant in the proximal part of the trachea. Secretions from this gland cover the ciliary surface

Question 13

Tunica muscularis- trachea

Answer 13

Smooth muscles (includes the trachealis muscle) that connects open ends of cartilages

Question 14

Tunica adventitia/serosa- trachea

Answer 14

A loose connective tissue that is continuous with the connective tissue of the neck (adventitia) OR covered by mediastinal mesothelium in thorax (serosa)

Question 15

Trachealis muscle

Answer 15

Muscle that connects the strips of cartilage that surround the trachea
- Outside for dogs and cats, inside of cartilage for other animals

Question 16

What covers the lungs?

Answer 16

Visceral pleura (connective tissue lined with mesothelium)

Question 17

Intrapulmonary air passages

Answer 17

Includes the bronchi and terminal bronchioles

Question 18

Bronchus (bronchi)

Answer 18

• Extrapulmonary primary bronchus divides and enters each lobe of the lungs and becomes the lobar or secondary bronchus
• Similar structure to the trachea or extrapulmonary bronchus although the layers do become thinner
• Epithelial height and number of mucous secreting cells and basal cells decrease from proximal to distal end of bronchus
• Clara cells increase in number from proximal to distal

Question 19

Lamina muscularis mucosa- lungs

Answer 19

A few smooth muscle fibers that separate the lamina propria from the tunica submucosa

Question 20

Tunica submucosa- lungs

Answer 20

• Loose irregular connective tissue rich in seromucous glands (number of glands decreases distally)
• Presence of hyaline cartilage as small multiple plates or as broken pieces of big cartilage encircling lumen. Amount of cartilage also decreases distally
• Blends into the tunica adventitia

Question 21

Terminal Bronchiole

Answer 21

• Bronchi branch repeatedly and finally give rise to terminal bronchioles.
• Lack cartilagionous support
• Lined by simple columnar or cuboidal epithelium with both ciliated and non-ciliated clara cells

Question 22

Clara cells

Answer 22

Cuboidal cells that are secretory in nature with abundant rER in the basal region

Functions
- Produce surfactant
- Secrete enzymes for mucus breakdown
- Possesses sER containing cytochrome P450 for metabolizing xenobiotic compounds
- Help secrete IgA
- Lysozymes to combat bacteria and viruses

Question 23

Propria-submucosa-lungs

Answer 23

Rich in elastic fibers and smooth muscle cell but it lacks any glands or cartilage

Question 24

Tunica muscularis- lungs

Answer 24

Layers of smooth muscles

Question 25

Tunica adventitia- lungs

Answer 25

Loose connective tissue surrounding the tunica muscularis

Question 26

Gas exchange area

Answer 26

• Respiratory bronchiole
• Alveolar ducts, sacs, and atrium
• Alveoli

Question 27

Respiratory bronchioles

Answer 27

• Similar in structure to terminal bronchioles except walls have out pockets that are continuous with alveoli
• Epithelium in carnivores is only clara cells
• Well developed in primates and horses, poor in horses and rare in other animals

Question 28

Alveolar ducts, sacs, and atriums

Answer 28

• A respiratory or terminal bronchiole will hoin multiple alveolar ducts that are lined with alveoli
• Ducts terminate in groups to form sacs. Atrium is the common space where the sacs open into

Question 29

Alveolar cells

Answer 29

• Functional unit for gas exchange
• Squamous and cuboidal cells