Histology by M Rais Khan

24/05/2025

21/05/2025

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19/03/2025

Liver
The histology of the liver reveals a complex structure designed for metabolism, detoxification, and bile production. It consists of lobules, hepatocytes, sinusoids, and Kupffer cells, among other components.

1. Liver Lobules (Structural Units)

The liver is organized into hexagonal lobules, each centered around a central vein.

At the corners of lobules are portal triads, consisting of:

Hepatic artery (supplies oxygenated blood)

Portal vein (brings nutrient-rich blood from the intestines)

Bile duct (carries bile to the gallbladder)

2. Hepatocytes (Liver Cells)

The main functional cells of the liver.

Polygonal in shape, arranged in cords separated by sinusoids.

Functions: metabolism, detoxification, bile production, and protein synthesis.

3. Sinusoids (Liver Capillaries)

Lined by fenestrated endothelial cells, allowing exchange between blood and hepatocytes.

Contain Kupffer cells (liver macrophages) that help in phagocytosis of pathogens and old RBCs.

Stellate (Ito) cells store vitamin A and regulate fibrosis.

4. Space of Disse

A perisinusoidal space between hepatocytes and sinusoidal endothelial cells.

Facilitates nutrient and plasma exchange.

5. Bile Canaliculi

Small ducts between hepatocytes that collect bile.

Drain into bile ducts of the portal triad.

13/03/2025

🌿 World Kidney Day 2025 🌿
"Your kidneys work tirelessly to keep you healthy—let’s return the favor! Stay hydrated, eat balanced meals, exercise regularly, and get your kidneys checked. Prevention is the key to a healthier future.

13/03/2025

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07/03/2025

Admissions are open in BACHELOR OF EASTERN MEDICINE SYSTEM with NUSKHA E TALEEM SCHOLARSHIP BASIS

06/03/2025

The lesser sac (also called the omental bursa) is a part of the peritoneal cavity located behind the stomach and lesser omentum. It is an important space in abdominal anatomy with clinical significance in conditions like pancreatitis and gastric perforations.

Boundaries of the Lesser Sac:

1. Anteriorly:

Lesser omentum (contains the hepatoduodenal ligament)

Stomach

Gastrocolic ligament

2. Posteriorly:

Pancreas

Left kidney and adrenal gland

Transverse mesocolon

3. Superiorly:

Caudate lobe of the liver

Diaphragm

4. Inferiorly:

Transverse colon

Greater omentum

5. Left Side:

Gastrosplenic ligament

Splenorenal ligament

Spleen

6. Right Side:

Opens into the greater sac through the epiploic foramen (of Winslow)

Epiploic Foramen (Foramen of Winslow) - Entrance to the Lesser Sac:

This foramen connects the lesser sac to the greater sac and is bounded by:

Anteriorly: Hepatoduodenal ligament (containing portal vein, hepatic artery, bile duct)

Posteriorly: Inferior vena cava

Superiorly: Caudate lobe of the liver

Inferiorly: First part of the duodenum

Clinical Significance:

Internal Hernias: Loops of intestine may herniate into the lesser sac through the foramen of Winslow.

Pancreatitis: Pancreatic fluid collections can extend into the lesser sac.

Gastric Perforation: Perforated posterior gastric ulcers may lead to fluid accumulation in the lesser sac.

04/03/2025

Histology of Gastric Glands

The gastric glands are specialized exocrine glands located in the mucosa of the stomach. They are responsible for secreting digestive enzymes, acid, and mucus to aid in digestion. The histological structure of gastric glands varies based on their location in the stomach:

1. Layers of the Gastric Mucosa

The gastric glands are found in the mucosa, which consists of:

Epithelium: Simple columnar epithelium forming gastric pits

Lamina propria: Loose connective tissue with blood vessels and immune cells

Muscularis mucosae: Thin smooth muscle layer

2. Types of Gastric Glands

There are three main types of gastric glands based on their location:

1. Cardiac Glands (found in the cardia)

Mostly mucous-secreting cells

Protect the esophagus from gastric acid

2. Fundic (Oxyntic) Glands (found in the fundus and body)

Chief cells → Secrete pepsinogen (inactive form of pepsin)

Parietal cells → Secrete HCl and intrinsic factor (for vitamin B12 absorption)

Mucous neck cells → Secrete mucus for protection

Enteroendocrine cells → Secrete hormones like gastrin, serotonin, and somatostatin

3. Pyloric Glands (found in the pylorus)

Predominantly mucous-secreting cells

G cells → Secrete gastrin, which stimulates acid secretion

3. Histological Features of Gastric Glands

Gastric pits open into the gastric glands

The glands extend deep into the lamina propria

Parietal cells (pink/eosinophilic) are large and round with a central nucleus

Chief cells (basophilic) have a granular cytoplasm due to pepsinogen secretion

Enteroendocrine cells are difficult to identify without special staining.

19/02/2025

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The cisterna chyli
It is a dilated sac-like structure in the lymphatic system that serves as the primary drainage point for lymph from the lower half of the body. Here’s an overview of its anatomy:

Location:

Positioned anterior to the first and second lumbar vertebrae (L1–L2).

Lies just to the right of the abdominal aorta and posterior to the right crus of the diaphragm.

Structure & Function:

It is an elongated, sac-like dilation of the thoracic duct, acting as a collecting reservoir for lymph.

Receives lymph from the lumbar lymphatic trunks (draining the lower limbs and pelvis) and the intestinal trunk (draining the gastrointestinal tract).

It continues superiorly as the thoracic duct, which carries lymph toward the venous system at the junction of the left subclavian and internal jugular veins.

Clinical Significance:

Enlargement of the cisterna chyli may occur due to obstruction or excessive lymphatic drainage.

Damage to the cisterna chyli during abdominal surgery can lead to chylous ascites (accumulation of lymph in the peritoneal cavity).

04/02/2025

The gastrointestinal tract (GIT) has four basic histological layers, from innermost to outermost:

1. Mucosa

Epithelium: Varies based on function (e.g., stratified squamous in the esophagus for protection, simple columnar in the stomach and intestines for secretion and absorption).

Lamina propria: Loose connective tissue with blood vessels, lymphatics, and immune cells.

Muscularis mucosae: Thin smooth muscle layer that helps in local movement and secretion.

2. Submucosa

Dense connective tissue with blood vessels, lymphatics, and nerves.

Contains the Meissner’s plexus (submucosal plexus), which controls secretion and blood flow.

3. Muscularis Externa

Two layers of smooth muscle: inner circular and outer longitudinal layers.

Auerbach’s plexus (myenteric plexus) is located between these layers and controls motility.

In the stomach, there is an additional oblique muscle layer for churning food.

4. Serosa (or Adventitia)

Serosa: A thin layer of loose connective tissue covered by the visceral peritoneum in intraperitoneal organs.

Adventitia: Present in retroperitoneal organs; composed of connective tissue that blends with surrounding structures.

Each layer plays a crucial role in digestion, absorption, and motility.