Histology Slides Database

Saturday, October 8, 2011

HISTOLOGICAL Comparison Between Bronchus & Bronchiole

Parameter	Bronchus	Bronchiole
Dimensions	Long, wide and its lumen is patent (not collapsed)	Short, narrow and its lumen may be collapsed as in bronchial asthma
Mucosa	Folded and lined by pseudostratified columnar epithelium (formed of seven types of cells similar to the tracheal tree)	Highly folded and lined with simple columnar ciliated or with cuboidal non-ciliated cells alternating with Clara cells
cell receptors	Few	Many
Goblet cells	Present	Absent (few only in large bronchioles)
Lymphoid follicles In C.T. „	Many	Absent
GlandS	Present	Absent
Plates of cartilage	Present	Absent

Comparison Between Bronchus & Bronchiole

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Histology of a BRONCHIOLE:

Histology of a BRONCHIOLE: When diameter of the tube reaches about 1mm, the cartilage disappears from the wall and structure is known as bronchiole.

The epithelium is pseudostratlfled dilated and contain very few goblet cells which are completely absent beyond terminal bronchiole. The epithelium is folded. The smooth muscle Is disposed in spiral manner like bronchi; being the most prominent feature of bronchiole.

The terminal bronchioles are lined with simple columnar or cuboldal epithelium. Few Clara cells are also seen.

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DETAILED HISTOLOGY OF INTRAPUMONARY BRONCHI

SECONDARY BRONCHUS: It has histology almost similar to that of primary bronchus .

TERTIARY BRONCHUS: The epithelium is tall columnar but not pseudostratlfled. Goblet cells are fewer in number.

The lamina propria is thin, elastic and completely encircled by smooth muscles arranged in a spiral manner.

The submucosa has fewer glands.

Cartilage framework is reduced to few Irregular plates. The submucosa merges with adventitia and then with alveoli.

SMALLER BRONCHI: In the wall of smaller bronchi, the hyaline cartilage is present as small isolated cartilagenous plates or islands of cartilage called Insulae cartllagenae.

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DETAILED HISTOLOGY OF PRIMARY (EXTRAPULMONARY) BRONCHUS

DETAILED HISTOLOGY OF PRIMARY (EXTRAPULMONARY) BRONCHUS

Histology of this is similar to that of trachea except for following differences .

A. Respiratory epithelium is less tall

B. Goblet cells are fewer in number

C. Lamina propria is more dense with large amount of elastic fibers

D. Trachealis muscle spreads out as a discontinuous layer of smooth muscle, which becomes progressively weaker downwards to surround the lumina of bronchi.

E. Submucosa has fewer seromucous glands

F. Cartilages are arranged in flattened Interconnected plates rather C-shaped rings.

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DETAILED HISTOLOGY OF TRACHEA

The wall of trachea is formed of following layers from within outwards

1. MUCOSA: It is comprised of the following layers.

a. Epithelium of trachea is pseudostratlfled ciliated tall columnar with goblet cells.

The ciliary activity produces constant movements of glandular secretions towards the pharynx. The epithelium is comprised of following cells.

I. Columnar ciliated cells (each cell bears 300 cilia)

II. Goblet cells (secrete mucous material)

III. Brush cells: These are sensory receptor cells, which are columnar and non- ciliated. Microvilli are present.

Iv. Basal or short cells (act as stem cells): These occur in the depth of epithelium

between the bases of the other types of cells and are undifferentiated cells that give rise to goblet cells or ciliated cells.

v. Neuroendocrine (Kulchltsky) cells

vl. Migrating lymphocytes and

vll. Migrating mast cells.

vlll. Dendritic cells: A network of dendritic cells lies along the base of tracheal epithelium which function as antigen-presenting cells, i.e.. these bind the antigens and then present it to the T-lymphocytes. All these cells are evident on electron microscope; while on light microscope, one can see'only columnar ciliated cells, goblet cells and basal cells.

The tracheal epithelium is supported by a thick basement membrane.

Beneath basement membrane lamina propria consists of loose highly vascular connective tissue, which becomes condensed at its deeper aspects to form a band of fibroelastic tissue (clear elastic membrane).

II. SUBMUCOSA: It contains loose areolar C.T. numerous mixed seromucous and mucous tracheal glands (which decrease in number in lower part of trachea), nerves, vessels and lymphoid follicles.

III. CARTILAGE: The submucosa merges with the perichondrium of the underlying hyaline cartilage. These cartilages (16-20) are found in the form of C-shaped rings. Between the two ends of C-shaped cartilages the submucosa directlv merges with the external adventitial layer. Bands of smooth muscles (trachealls) join the free ends of the rings posteriorly. The contraction of muscle and resultant narrowing of the tracheal lumen are useful in cough reflex.

IV. ADVENTITIA/FIBROSA: it is formed of areolar C.T. containing small blood vessel and autonomic nerves to trachea.

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The ultrastructure of hepatocytes

The ultrastructure of hepatocytes differs In the three zones. As gluconeogenesis occurs primarily in zone I; so SER is sparse, mitochondria are elongated and glycogen is more abundant.

As glycolysis and lipid metabolism is frequent in zone III, so SER is well developed here and the mitochondria are numerous and quite small. The glycogen is sparse.

The hepatocytes of zone II show intermediate features.

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Histology Of Liver or Hepatic Acinus

Liver or Hepatic Acinus: It is the most preferred structural and functional unit of the liver now days. In cross section, it is a diamond-shaped or elliptical subdivision of liver parenchyma. It comprises parts of two adjacent hepatic lobules; the narrower ends of diamond are formed by two central veins, while the central wider part is formed by two portal triads (vascular core). The hepatic acinus is commonly divided into three zones (table 10.12).

Zone I is formed by the central part of liver acinus, which is present at the junction of adjacent sides, or peripheral parts of two hexagonal hepatic lobules. It receives best of the nutritive and oxygenated blood (through hepatic artery and portal vein), so hepatocytes of zone I are more liable to metabolic changes (like storage and depletion of glycogen). Similarly it is more liable to damage by toxins (eclampsia), phosphorous poisoning, chronic hepatitis and primary biliary cirrhosis.

Zone II is intermediate in position and less affected by the conditions producing changes in zones I and ill. However, it undergoes necrosis in yellow fever.

The peripheral zone (zone III) (hepatocytes of a liver acinus present nearer to central veins) receives less oxygenated and nutritive blood, so more liable to damage by hypoxia. It also undergoes necrosis in drug and chemical toxicity and right-sided cardiac failure.

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