Histology Slides Database: October 2011

Saturday, October 8, 2011

Histological comparison Between various Tubules of Kidney

Histological comparison Between various Tubules of Kidney

Parameter	Proximal Convoluted tubule	Loop of Henle	Distal Convoluted Tubule	Collecting tubule
Length	15 mm		5 mm
Diameter	60 nm	12-15 jim	20-50 nm
Lumen	Smaller (because of brush border)	Larger	Larger (because of lack of brush border)	Larger
Convoluted	More		Less
Epithelium	Simple columnar epithelium	Simple squamous epithelium	Simple cuboidal epithelium	Simple cuboidal epithelium
Number of eells/T.S. of tubule	6-12	6-12	5-8 (but up to 20 at its macula densa)	15-20
Nuclel/T.S. of tubule «	3-5, large, centrally located and rounded	6-12 and are centrally located	6-8 and appear to be bulging into the lumen	15-20 and are centrally located
Apical canaliculi	Present	Absent	Absent	Absent
Luminal surface of epithelial cells	Brush border (striated)			Basal striations
Lateral cell boundaries	Not clear	Not clear	Not clear	Clearly demarcated
Apical brush border of cells (microvilli)	Well-developed & possess phosphate enzymes	Only few microvilli	Not-well developed	Few microvilli
Cytoplasmic basal acidophilic mitochondrial strlatlons	Well-developed	Absent	Present but faintly stained	May be seen in some cells but poorly stained
Cytoplasm	Deeply acidophilic & more granular	Pale staining	Less acidophilic & less granular	Very pale staining
Reabsorptlon	Actively absorb glucose, amino acids & proteins		Absorb sodium due to aldosterone	Water
Excretion	Certain dyes & drugs (penicillin)		Sodium & potassium due to vasopressin

comparison Between various Tubules of Kidney

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Histology Of Collecting Tubules

Collecting Tubule:

It is excretory . In renal cortex it lies in medullary ray and running straight, passes into medulla where 6-8 collecting ducts join to form larger straight ducts called papillary ducts of Balllnl, which open at the apex of papilla.

Collecting tubules and ducts are lined by simple cuboidal epithelium with distinct lateral borders of cells. The cytoplasm Is poorly stained and has a small dark central nucleus. There is no brush border or basal strlatlons. The papilla is lined by stratified squamous epithelium.

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Histology Of Bowman's Capsule:

Histology Of Bowman's Capsule:

It is a double-walled capsule comprising of outer parietal and inner visceral layers and a space between two layers, which is known as urinary space.

Parietal layer is made up of simple squamous epithelium with reticular fibres.

Its basal lamina covers outer surface of flat cells. At urinary pole it continues with simple low columnar epithelium of PCT.

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Histology Of a Nephron:

Each kidney contains approximately 1-4 million nephrons.

There are two types of nephrons;

The cortical nephrons have short Henles loop while

Juxta- medullary nephrons have long loop of Henle.

Each nephron begins as a double-walled, cup-shaped dilatation known as Bowman's capsule.

A tuft of 50 capillaries called glomerulus occupies the concavity of Bowman's capsule.

The Bowman's capsule and glomerulus are collectively known as Malphlglan corpuscle (renal corpuscle).

Each corpuscle (200 nm in diameter) consists of Bowman's capsule, glomerulus of capillaries, afferent and efferent arterioles and mesanglal cells.

From the Bowman's capsule's basal region, the proximal convoluted tubule (PCT) arises which continues downward into loop of Henle (LOH).

This loop ascends up to continue into distal convoluted tubule (DCT), which joins the collecting tubules. The renal corpuscles, proximal and distal convoluted tubules lie in the cortex of kidney while loops of Henle lie in the medullary rays.

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Histology Of Uriniferous Tubules

The parenchyma of kidney consists of a large number of closely packed Uriniferous tubules.

Each uriniferous tubule comprises of two parts, which form a continuous passage:

(1) Nephron: It is 30-40 mm long and is responsible for secretion of urine.

(2) Collecting Tubule (Excretory Duct): It has a length of 20 mm and conveys urine to renal pelvis.

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Histology Of PULMONARY ALVEOLI:

Histology Of PULMONARY ALVEOLI:

These open directly into alveolar sacs or alveolar ducts or respiratory bronchioles and are lined by two types of squamous epithelial cells (pneumocytes).

I. Type-l cells:

Squamous alveolar cells are most numerous (97%) and form a very thin but complete lining of all alveoli. These cells possess a low flat nucleus and minimum cytoplasm. These possess microvilli at their alveolar surface.

These have thin basement membrane, which fuses with basement membrane of endothelium of blood capillaries. These cannot divide. Main role of these cells is to provide a barrier of minimal thickness that is readily permeable to gases as well as these contain pinocytotic vesicles suggesting a probable role in surfactant turnover.

II. Type-ll Cells/Great Alveolar Cells/Secretory Cells/ Septal Cells (3%):

These are cuboldal In shape and occur in the form of groups present at corners of alveolar walls. Luminal surfaces of these cells bear microvilli. Their cytoplasm gives a vacuolated appearance due to presence of lamellar bodies of 1-2 nm in diameter (cytosomes), which contain phospholipids, proteins and glycosaminoglycans. These substances are secreted into alveoli as surfactant.

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Detailed Histology Of Alveolar sacs (air sacs) and Inter-Alveolar Septum

Detailed Histology Of Alveolar sacs (air sacs):

These are groups of cup shaped structures (alveoli with 200 nm diameter and are the structural and functional units of respiratory gas exchange) with very thin walls and open into a common central space Because of interdigitating arrangement each alveolus does not have a completely separate wall. Adjacent alveoli are separated from each other by Interalveolar septa.

INTERALVEOLAR SEPTUM: It is the two layers of squamous epithelial cells in between which lies the Interstltlum possessing richest capillary network of the body, fibroblasts, elastic and reticular fibres and macrophages. The interalveolar septum is composed of: (1) capillary endothelial type cells (30%); (2) type I pneumocytes (08%); (3) type II pneumocytes (16%); interstitial cells (mast cells and fibroblasts etc.) (36%) and; (4) alveolar macrophages (10%).

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Histology Of ALVEOLAR DUCTS:

Histology Of ALVEOLAR DUCTS:

The respiratory bronchioles continue into thin walled small tubes called alveolar ducts .The walls of these ducts are studded with alveolar sacs and alveoli, which open into lumen of the duct.

The lining epithelium is simple squamous or low cuboldal.

The lamina propria consists of smooth muscles and connective tissue containing elastic and collagen fibers.

Alveolar ducts terminate into pulmonary atria, which are Irregular spaces from which alveolar sacs and alveoli diverge. Elastic and reticular fibers form a complex network encircling the opening of atria, alveolar sacs and alveoli.

The elastic fibers enable the aiveoli to expand with inspiration and contract passively with expiration.

Reticular fibres serve as a support that prevent overdistension and damage to delicate capillaries as well as thin alveolar septa.

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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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Histology of Portal Lobule and Hepatic Lobule

Portal Area/trlad/canal: It is present at the periphery of hepatic lobule. Each portal area comprises of branches of portal vein, hepatic artery, bile duct and lymphatic vessels lying in small amount of connective tissue. Around the periphery of hepatic lobules can be seen several portal canals within the interlobular septa.

Hepatic lobule is the structural unit of liver while the functional unit is portal lobule. The recent studies have suggested another functional unit of liver, the hepatic acinus.

Portal Lobule: Portal area or portal canaJ is present at the center of portal lobule. Portal lobule consists of liver tissue draining bile into the bile duct of that portal area. Such a unit is triangular in cross section, containing part of three adjacent classic hepatic lobules and has central vein at each of three corners. This represents the area of drainage for radical of a bile duct present in the portal canal.

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Histology Of The duct system for the biliary passage

Histology Of The duct system for the biliary passage: The sides of hepatocytes related to sinusoids are referred to as sinusoidal domains while the sides related to other hepatocytes are referred to as lateral domains. The bile secreted by hepatocytes passes initially into bile canaliculi (0.5-1.5 |im), which are the intercellular canals (midway of lateral domains). So these bile canaliculi are simple spaces between adjoining liver cells and have no other lining epithelium. These canals anastomose with each other and pass to the periphery of hepatic lobules where these empty into short canals known as canals of Herlng Preductules/Cholangloles: The cholangioles are lined by simple cubical epithelium and drain in to bile ductules, which drain into bile ducts.

The bile ductules and bile ducts are lined by simple cubical epithelium. The intrahepatic ducts (lined by simple columnar epithelium) by the union of bile ducts, the intrahepatic ducts lead to extrahepatic ducts which are lined by simple columnar epithelial surrounded by C.T. and smooth muscles. These unite to form the common bile duct, which is also lined by simple columnar epithelium surrounded by C.T. and smooth muscle cells. The C.T. contains tubule-alveolar mucous glands.

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Detailed histology Of HEPATOCYTES

Detailed histology Of HEPATOCYTES

The hepatocytes are polyhedral (5-12 sides) in shape (80% of cell population) with mostly single rounded nucleus. 25% of hepatocytes are binucleated. Each nucleus contains prominent nucleolus.

The plasma membrane of hepatocytes bear microvilli more numerous towards sinusoids than towards bile canaliculus). The cytoplasm of hepatocytes is acidophilic due to richness in smooth endoplasmic reticulum and glycogen but contains basophilic bodies as well due to RER.

The hepatocytes are arranged in radiating plates of one to two cell thicknesses around the central vein. These cords or plates of hepatocytes branch and anastomose with other cords and in this way form a three dimensional framework of liver parenchyma.

The hepatic plates are separated from each other by blood sinusoids and by perisinusoidal tissue spaces (spaces of Dlsse). The sinusoids are lined by two types of cells; the simple squamous endothelial cells (non-continuous epithelium) and von Kupffer cells (stellate shaped phagocytic cells of reticuloendothelial system or mononuclear phagocytic or macrophage system). The plasma escaping from sinusoids passes out into the perisinusoidal space, which surrounds the sinusoids.

So perisinusoidal space is present between the hepatic sinusoids and hepatocytes. This space contains reticular fibres, stellate-shaped adipocytes (lipocytes or Ito cells), plasma (tissue fluid) and microvilli of hepatocytes. Ito cells are typical stellate shaped cells. Space of Disse continues into space of MalL, which contains structures of portal triad. The lymphatic vessels also begin in the spaces of Mall along with other structures of portal triad. The liver produces 50% of the lymph found in the thoracic duct.

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Histology Slides Database

Saturday, October 8, 2011

Histological comparison Between various Tubules of Kidney

Histology Of Collecting Tubules

Histology Of Bowman's Capsule:

Histology Of a Nephron:

Histology Of Uriniferous Tubules

Histology Of PULMONARY ALVEOLI:

Detailed Histology Of Alveolar sacs (air sacs) and Inter-Alveolar Septum

Histology Of ALVEOLAR DUCTS:

HISTOLOGICAL Comparison Between Bronchus & Bronchiole

Histology of a BRONCHIOLE:

DETAILED HISTOLOGY OF INTRAPUMONARY BRONCHI

DETAILED HISTOLOGY OF PRIMARY (EXTRAPULMONARY) BRONCHUS

DETAILED HISTOLOGY OF TRACHEA

The ultrastructure of hepatocytes

Histology Of Liver or Hepatic Acinus

Histology of Portal Lobule and Hepatic Lobule

Histology Of The duct system for the biliary passage

Detailed histology Of HEPATOCYTES

Questions related to Patent ductus arteriosus

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