أسئلة الثالثة هستولوجي - ريسب (قبل التعديل

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Questions and Answers

What is the primary function of alveolar pores in the respiratory system?

They provide nutritional support to alveolar cells.

They allow communication between alveoli. (correct)

They facilitate gas exchange.

They support structural integrity of alveoli.

Which cell type acts as the first line of defense in the lungs?

Dust cells (correct)

Type I alveolar cells

Interstitial fibroblasts

Endothelial cells

What type of particles do dust cells primarily phagocytose?

Dust and coal particles (correct)

Intravenous pathogens

Oxygen molecules

Excessive surfactant

What feature is characteristic of the cytoplasm of dust cells in smokers?

It is crowded with large, irregular, electron-dense bodies. Signup and view all the answers

Which of the following correctly describes the fate of dust cells after phagocytosing particles?

They migrate to bronchi and are expelled in sputum. Signup and view all the answers

What are the two main types of cells lining the alveoli?

Type 1 and Type 2 pneumocytes Signup and view all the answers

What is the main function of Type 2 pneumocytes?

To secrete pulmonary surfactant Signup and view all the answers

Which structures make up the interalveolar septum?

Type 1 and Type 2 pneumocytes along with connective tissue Signup and view all the answers

How do Type 1 pneumocytes primarily contribute to gas exchange?

By providing a very thin membrane for gas diffusion Signup and view all the answers

What is a defining characteristic of Type 2 pneumocytes as observed under an electron microscope?

They have rounded central nuclei and numerous lamellar bodies Signup and view all the answers

What role do interalveolar septa play in the structure of the alveoli?

They provide structural support between adjacent alveoli Signup and view all the answers

What percentage of the alveolar lining epithelium is made up of Type 2 pneumocytes?

5% Signup and view all the answers

What prevents alveolar collapse during respiration?

Pulmonary surfactant Signup and view all the answers

What is the primary histological structure that separates the air in the alveoli from the blood in the capillaries?

Alveolar capillary membrane Signup and view all the answers

Which statement best describes the structure of the interalveolar septa?

Fused basal laminae of alveolar and endothelial cells Signup and view all the answers

What characteristic of the cytoplasm of heart failure cells is notable?

Numerous vacuoles containing hemosiderin granules Signup and view all the answers

What is the ultimate fate of dust cells after they have phagocytosed foreign particles?

Migrate to the bronchi and are cleared via ciliary action Signup and view all the answers

Which type of cells contributes to the structure of the interalveolar septum, in addition to the alveolar epithelial cells?

Capillary endothelial cells Signup and view all the answers

Which statement accurately describes Type 1 pneumocytes?

They are flat squamous cells with a thickness less than 0.2 um. Signup and view all the answers

What is the primary role of pulmonary surfactant?

To decrease surface tension and prevent alveolar collapse. Signup and view all the answers

What type of cells are Type 2 pneumocytes classified as?

Cuboidal cells with a thin basal lamina. Signup and view all the answers

Which component surrounds the terminal bronchioles?

Connective tissue containing elastic and smooth muscle fibers. Signup and view all the answers

How do Type 2 pneumocytes differ from Type 1 pneumocytes in terms of percentage of lining epithelium?

Type 2 make up approximately 5% of the lining. Signup and view all the answers

What feature distinguishes Type 2 pneumocytes from Type 1 pneumocytes at the cellular level?

Round central nuclei and cytoplasmic granules. Signup and view all the answers

What are the alveolar sacs comprised of?

Clusters of alveoli opening into a shared central space. Signup and view all the answers

Which of the following best describes the structure of the interalveolar septum?

Consists of connective tissue and supports gas exchange. Signup and view all the answers

Study Notes

Respiratory System (Histology)

Respiratory Bronchioles: Arise from terminal bronchioles.
Lined By: Ciliated cubical cells (in some areas, non-ciliated cubical in smaller respiratory bronchioles).
Surrounded By: Connective tissue with elastic fibers and smooth muscle fibers.
Wall Is: Alveoli that open directly into the lumen.

Alveolar Ducts

Definition: Narrow tubes where alveoli open into their wall.

Pulmonary Alveoli

Definition: Minute air spaces; the functional and structural unit of the lung. Groups of alveoli that open into a common central space are called alveolar sacs.
Structure:
- Alveolar epithelium (Type 1 pneumocytes, Type 2 pneumocytes)
- Interalveolar septum
- Alveolar pores

Type 1 Pneumocytes

Number: 95% of lining epithelium.
LM: Flat squamous cells, less than 0.2 µm thick, with slightly thickened areas containing nuclei.
EM: Attached to each other by occluding (tight) junctions, have thin basal lamina; perinuclear cytoplasm contains small Golgi, few mitochondria, and rough endoplasmic reticulum (rER) while cytoplasm of the thin portion is devoid of organelles.
Function: Provide a very thin membrane for gas exchange.

Type 2 Pneumocytes

Number: 5% of lining epithelium.
Characteristics: Cuboidal cells with central nuclei located at the angles of interalveolar septa.
EM: Attached to Type 1 cells by occluding junctions. Cytoplasm contains many mitochondria, rER, prominent Golgi complex and electron-dense lamellar bodies rich in phospholipids.
Function: Act as progenitor cells for both Type 1 and Type 2 pneumocytes; secrete pulmonary surfactant.

Pulmonary Surfactant

Definition: A mixture of phospholipids that lines the inner aspect of alveoli.
Function: Decreases surface tension, preventing alveolar collapse.

Blood Air Barrier

Definition: The wall separating air in alveoli from blood in capillaries.
Structure: Includes Type 1 alveolar cells, fused basal laminae of alveolar and endothelial cells of capillaries, and endothelial cells of capillaries.

Alveolar Pores (Pores of Kohn)

Description: Holes in the interalveolar septa that connect the alveoli.
Importance: Facilitate communication and equalization of pressure between alveoli.

Alveolar Macrophages

Definition: Mononuclear phagocytes in the lungs, representing the first line of defense.
Site: Interalveolar septum, on luminal surface of alveoli.
Origin: Blood monocytes.
Shape: Branched cells with pseudopodia.
Cytoplasm: Vacuolated, contains many lysosomes.
Types:
- Dust cells: Phagocytose dust or coal particles. In smokers, cytoplasm is crowded with large irregular heterogeneous electron-dense bodies.
- Heart failure cells: Phagocytose extravasated red blood cells (RBCs). In heart failure, cytoplasm contains many vacuoles with hemosiderin granules.
Fate: Migrate to bronchi via ciliary action, swallowed and expelled in sputum.

Interalveolar Septum

Structure:
- Alveolar epithelium on either side.
- Capillary network (pulmonary capillary bed).
- Supporting network of reticular and elastic fibers and connective tissue cells (septal cells, mast cells, lymphocytes, white blood cells [WBCs]).
- Basement membranes of alveolar epithelium and capillary beds.
Additional Note: The two basement membranes often fuse to form the alveolar-capillary membrane.

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Description

Test your knowledge on the histological structure of the respiratory system. This quiz covers respiratory bronchioles, alveolar ducts, and the different types of pneumocytes. Understand the key features and functional significance of the lung's microscopic anatomy.