Connective Tissues Classification

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Questions and Answers

What type of cells are responsible for the synthesis of ECM components?

Macrophages

Pericytes

Fibroblasts (correct)

Fibrocytes

What is the main function of connective tissue proper?

Providing structural support

Serving as a medium for exchange

Aiding in the defense and protection of the body

All of the above (correct)

Which type of cells are observed during wound healing?

Myofibroblasts (correct)

Mast cells

Macrophages

Fibrocytes

What are the two elements that connective tissue is composed of?

Cells and extracellular matrix Signup and view all the answers

What is the function of adipose tissue?

Forming a site for storage of fat Signup and view all the answers

Which type of cells are long-living and can survive for months in tissues?

Macrophages Signup and view all the answers

What is the function of macrophages?

Phagocytosing foreign substances Signup and view all the answers

What is the function of connective tissue proper in organs?

Forming the capsules of organs and membranes Signup and view all the answers

What is the main difference between fibroblasts and fibrocytes?

Fibroblasts are active, fibrocytes are quiescent Signup and view all the answers

What is the origin of macrophages?

Monocytes of blood Signup and view all the answers

Where are mucosal mast cells typically found?

Connective tissue of the intestinal mucosa and lungs Signup and view all the answers

What type of immunoglobulin is produced by plasma cells and binds to mast cell receptors?

IgE Signup and view all the answers

What triggers the degranulation process in mast cells?

Cross-linking of IgE molecules by an antigen Signup and view all the answers

What is the result of the degranulation process in mast cells?

Release of chemical mediators promoting allergic reactions Signup and view all the answers

Where are connective tissue mast cells typically found?

Skin and peritoneal cavity Signup and view all the answers

What is the outcome of the intracellular fusion of specific granules and exocytosis?

Release of chemical mediators Signup and view all the answers

What happens to the mast cell after degranulation?

The cell synthesizes new granules Signup and view all the answers

What is the role of IgE molecules in the degranulation process?

To bind to surface receptors on mast cells Signup and view all the answers

What is the result of the release of histamine and leukotriens from mast cells?

Increased capillary permeability Signup and view all the answers

What is the term for the movement of leukocytes through the walls of capillaries and postcapillary venules?

Diapedesis Signup and view all the answers

What is the result of the activation of B lymphocytes by antigens?

Formation of plasma cells Signup and view all the answers

What is the main function of adipose cells?

Storage of neutral fats Signup and view all the answers

What is the term for the proteins that polymerize into elongated structures in connective tissue?

Fibers Signup and view all the answers

What is the main component of ground substance in connective tissue?

Glycosaminoglycans (GAGs) Signup and view all the answers

What is the function of fibroblasts in connective tissue?

Formation of the extracellular matrix Signup and view all the answers

What is the average lifespan of plasma cells?

10-20 days Signup and view all the answers

What is the primary function of macrophages in regards to foreign substances and bacteria?

To phagocytose them Signup and view all the answers

What is the term for macrophages that process and present antigens to other cells?

Antigen Presenting Cells (APC) Signup and view all the answers

What is the name of the cells that macrophages can fuse to form in certain conditions?

Multinuclear giant cells Signup and view all the answers

What is the main function of histamine secreted by mast cells?

To increase vascular permeability Signup and view all the answers

What is the term for the cells that are distributed throughout the body and have special names in certain regions?

Macrophages Signup and view all the answers

What is the function of heparin secreted by mast cells?

To act as an anticoagulant in the blood Signup and view all the answers

What is the shape of the nucleus in mast cells?

Small and spherical, situated centrally Signup and view all the answers

What is the function of collagenase secreted by macrophages?

To break down collagen in the extracellular matrix Signup and view all the answers

What is the main function of multilocular adipose tissue in human newborns?

To produce heat Signup and view all the answers

What percentage of the body weight does multilocular adipose tissue constitute in human newborns?

2-5% Signup and view all the answers

What is the role of leptin in weight regulation?

Appetite-suppressing hormone Signup and view all the answers

What is the characteristic shape of nuclei in multilocular adipose cells?

Spherical and central Signup and view all the answers

What is the source of estrogens in postmenopausal women?

Adipose tissue Signup and view all the answers

What is the term for the uncoupling protein found in the mitochondria of multilocular adipocytes?

Thermogenin Signup and view all the answers

What is the percentage of body weight represented by adipose tissue in men of normal weight?

15-20% Signup and view all the answers

What is the term for the type of obesity characterized by an increase in the number of adipose cells?

Hyperplastic obesity Signup and view all the answers

Study Notes

Categories of Connective Tissues

Embryonic connective tissues:
- Mesenchymal
- Mucous
Adult connective tissues:
- Specialized connective tissues
- Connective tissue proper
- Supporting tissues
- Adipose tissue

Characteristics of Connective Tissues

Origin: Mesenchyme
Structure: Cells and extracellular matrix (ECM)
Cells are widely separated by ECM components

Components of Connective Tissues

Cells:
- Fibroblasts
- Fibrocytes
- Adipoblasts
- Adipocytes
- Chondroblasts
- Chondrocytes
- Osteoblasts
- Osteocytes
- Formed elements (erythrocytes, leukocytes)
Extracellular matrix (ECM):
- Fibers: Collagen, elastic, reticular
- Ground substance: Glycosaminoglycans (GAGs), proteoglycans, multiadhesive glycoproteins

Functions of Connective Tissues

Providing structural support
Serving as a medium for exchange
Aiding in defense and protection of the body
Forming a site for storage of fat

Connective Tissue Proper

Forms capsules of organs and membranes
Forms trabeculae and walls inside organs
Medium for exchange of metabolic waste, nutrients, and oxygen between blood and cells

Cells of Connective Tissue Proper

Fibroblasts:
- Originate from undifferentiated mesenchymal cells
- Produce ECM components
- Can proliferate
Fibrocytes:
- Quiescent fibroblasts
- Smaller than fibroblasts
- Fewer processes
- Smaller, darker, elongated nucleus
- Small amount of RER

Pericytes and Myofibroblasts

Pericytes: Major source of myofibroblasts during fibrosis in multiple organs
Myofibroblasts:
- Combine features of fibroblasts and smooth muscle cells
- Produce ECM and contain actin and myosin filaments
- Observed during wound healing
- Responsible for wound contraction after tissue injury

Resident Cells of Connective Tissue

Macrophages:
- Derived from monocytes of blood
- Mature and acquire morphological features of macrophages
- Long-living cells, can proliferate locally
- Distributed throughout the body
- Have different names : kupffer cells , microglia and osteoclast
Mast cells:
- Derive from stem cells of bone marrow
- Oval to round connective tissue cells
- Contain basophilic secretory granules
- Small, spherical nucleus
Leukocytes:
- Wandering cells of connective tissue
- Migrate through walls of capillaries and postcapillary venules from blood into connective tissue
Plasma cells:
- B lymphocyte + antigen → B lymphoblast (mitotic division) → B lymphocyte + plasma cell
- Large, ovoid cells with basophilic cytoplasm
- Well-developed RER
- Spherical nucleus
Adipose cells:
- Fat cells
- Store neutral fats or produce heat

Adipose Tissue

Multilocular adipose tissue (brown fat):
- Polygonal cells with multiple lipid droplets
- Rich in capillaries
- Receives direct sympathetic innervation
- Important in newborns for heat production
- Found mainly around shoulder blades and kidneys

Function of Multilocular Adipose Tissue

Produces heat
Stimulated by nerve impulses releasing epinephrine
Lipase releases fatty acids, metabolized to produce heat
Thermogenin (UCP1) in mitochondria dissipates energy as heat
Warmed blood circulates throughout the body

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Description

Learn about the classification of connective tissues, including embryonic, adult, loose, dense, and specialized types.