Connective Tissue Characteristics and Functions

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Questions and Answers

What is a primary function of multilocular adipocytes found in brown fat?

Synthesis of proteins

Heat generation (correct)

Production of hormones

Storage of energy

Which characteristic is NOT associated with macrophages?

Centrally located nucleus (correct)

Pale basophilic cytoplasm

Presence of pseudopodia

Irregular cell boundary

What is the role of reticular cells in reticular connective tissue?

Supportive function and multipotent stem cell activity (correct)

Nutrient absorption

Energy storage

Production of extracellular matrix

Identify a specific type of macrophage found in the liver.

Von-Kupffer cells Signup and view all the answers

In pathological conditions, macrophages can form which of the following cell types?

Epithelioid cells Signup and view all the answers

Which characteristic is NOT true about connective tissue?

Its cells are tightly packed together. Signup and view all the answers

Which of the following is NOT a type of connective tissue fiber?

Nervous fibers Signup and view all the answers

What is one of the primary functions of connective tissue?

Support and connection of cells and tissues. Signup and view all the answers

Which cell type is regarded as fixed in connective tissue?

Fibroblasts Signup and view all the answers

In what form does the extracellular matrix exist in bone connective tissue?

Firm Signup and view all the answers

What role do adipose cells primarily serve in connective tissue?

Lipid storage and metabolism. Signup and view all the answers

Which of the following best describes the nature of wandering free cells in connective tissue?

Short-lived and migratory. Signup and view all the answers

Which connective tissue function is primarily involved in the healing of injured tissues?

Support and connection. Signup and view all the answers

What is the primary function of undifferentiated mesenchymal cells (UMCs)?

To act as a multipotent stem cell Signup and view all the answers

Which cellular characteristic is NOT associated with fibroblasts?

Presence of adipocytes Signup and view all the answers

What significant role do myofibroblasts play in tissue repair?

Contracting to close wounds Signup and view all the answers

What is the appearance of unilocular adipocytes when observed under a light microscope?

Large cells with a signet-ring appearance Signup and view all the answers

Fibrocytes are best characterized by their:

Small, spindle shape with elongated dark nucleus Signup and view all the answers

What triggers a fibrocyte to revert to a fibroblast state during wound healing?

Adequate stimulation during healing Signup and view all the answers

How do fixed macrophages primarily contribute to connective tissue?

By mediating inflammation and debris removal Signup and view all the answers

What is a primary characteristic of the cytoplasm of fibroblasts observed under electron microscopy?

Prominent Golgi apparatus and mitochondria Signup and view all the answers

Study Notes

Connective Tissue General Characteristics

Connective tissue is derived from mesenchyme.
Composed of cells, fibers (collagen, elastic, reticular) and ground substance.
Cells are widely separated by a large amount of extracellular substance (matrix).
Matrix can be firm, hard, or fluid, depending on the type of connective tissue.
Often penetrated by blood vessels, lymphatics, and nerves.

Connective Tissue Functions

Support and connection of cells, tissues, and organs.
Cells provide healing of injured tissues.
Resist stress, as seen in cartilage, bone, tendons, ligaments, and organ capsules.
Medium for exchange, as blood, lymph, and connective tissue proper deliver nutrients, waste products, and signaling molecules.
Immunity, as plasma, mast cells, and white blood cells (WBCs) leave the bloodstream and enter connective tissue to protect the body.
Lipid storage and metabolism, performed by adipose cells and adipose tissue.

Connective Tissue Cells

Fixed Cells: Stable and long-lived cells.
- Fibroblasts
- Fat Cells
- Undifferentiated mesenchymal cells (UMCs)
- Fixed Macrophages
Wandering Free Cells: Transient and migrating cells from the blood to the connective tissue.
- Plasma Cells
- Mast Cells
- Leukocytes

Undifferentiated Mesenchymal Cells (UMCs)

LM: Small, irregular, branched, star-shaped cells with pale basophilic cytoplasm. Nucleus is large, oval, and centrally located with visible nucleoli.
EM: Few organelles, many free ribosomes.
Function:
- Multipotent stem cell that can differentiate into other connective tissue cells.
- In bone marrow they give rise to blood cells.

Fibroblast

Origin: Undifferentiated mesenchymal cells, pericytes.
Site: All types of connective tissue.
LM: Flat, branched cells with thin processes; oval nucleus with a prominent nucleolus. Basophilic cytoplasm.
EM: Euchromatic nucleus with a prominent nucleolus, RER, ribosomes, Golgi, mitochondria.
Function:
- Formation of connective tissue fibers.
- Formation of ground substance.
- Healing and repair of wounds.

Fibrocytes

LM/EM: Smaller, spindle-shaped with few processes, elongated, dark nucleus. Involved in wound closure.

Myofibroblasts

LM/EM: Similar to fibroblasts and smooth muscle cells. Contains actin and myosin.
Function: Responsible for wound closure.

Fat Cells - Unilocular Adipocyte (White Fat)

Site: White adipose tissue.
LM: Rounded or oval, large cells with a peripheral, flattened nucleus. Cytoplasm is pale and reduced to a thin rim around a large fat droplet. In H&E stains, fat dissolves, creating large vacuoles (signet-ring appearance). Stains orange with Sudan III.
EM: Fat droplets appear as electron-dense inclusions, with few cell organelles surrounding the nucleus.
Function: Storage of fat, support organs, and heat insulation.

Fat Cells - Multilocular Adipocyte (Brown Fat)

Site: Brown adipose connective tissue.
LM: Small rounded cell with a rounded nucleus and many small fat droplets. Contains many mitochondria, giving it a brown appearance.
Function: Heat generation.

Macrophages

Origin: Blood monocytes.
Site: Scattered in connective tissue or fixed to collagen fibers.
LM: Large, branched cell with an irregular cell boundary (pseudopodia) and a dark, kidney-shaped nucleus. Cytoplasm is pale basophilic and vacuolated.
EM: Pseudopodia, lysosomes, RER, Golgi.
Function:
- Phagocytic.
- Antigen-presenting cells (APCs).

Mononuclear Phagocytic System

Includes macrophages in different organs with specific names:
- Von Kupffer cells in the liver.
- Dust cells in the lung.
- Langerhans cells in the skin.
- Monocytes in the blood.
- Microglia in the brain.
- Osteoclasts in the bone.
- Macrophages in the spleen, thymus, lymph node, bone marrow, and connective tissue.
These cells share the same structure and function.

Reticular Cells

Origin: Undifferentiated mesenchymal cells (UMCs).
Site: Reticular stroma of parenchymatous organs (most common cell in reticular connective tissue).
LM: Shape: Small, branched cell with many processes (reticular fibers are attached to their processes). Stains: Hx & E → Pale basophilic. Special stain → Silver stain (brown). Nucleus: Central, oval, and pale.
Function:
- Multipotent stem cell, supportive function.
- Antigen-presenting cells (APCs).
- Phagocytic function.

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Description

This quiz focuses on the general characteristics and functions of connective tissue. Learn about its composition, the roles of various cells, and the importance of the extracellular matrix. Test your knowledge on how connective tissue supports, connects, and protects the body.