Connective Tissue Overview

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Questions and Answers

What is the embryonic origin of connective tissue?

Neuroectoderm

Endoderm

Mesoderm (correct)

Ectoderm

Which of the following is NOT a general function of connective tissue?

Medium for exchange of metabolites

Connects and binds cells and organs

Synthesizes hormones (correct)

Provides mechanical support

What characteristic distinguishes fixed connective tissue cells?

Undergoes rapid cell division

Secretes extracellular matrix

High level of mobility

Stays in one location (correct)

Which of the following types of connective tissue has a rubbery consistency?

Cartilage Signup and view all the answers

Which component is NOT part of connective tissue?

Myocytes Signup and view all the answers

What role does connective tissue play in wound healing?

Provides a framework for cellular repair Signup and view all the answers

What type of connective tissue is primarily fluid in nature?

Blood Signup and view all the answers

Which of the following is a characteristic of connective tissue?

Contains a large amount of intercellular substance Signup and view all the answers

What is the primary function of undifferentiated mesenchymal cells?

To differentiate into other cell types Signup and view all the answers

Which cell type is classified as stable and long-lived?

Macrophages Signup and view all the answers

What is a unique characteristic of undifferentiated mesenchymal cells as observed under light microscopy?

Central oval pale nucleus with clear nucleoli Signup and view all the answers

In response to injury, undifferentiated mesenchymal cells can differentiate into which of the following cell types?

Smooth muscle cells Signup and view all the answers

Which cell type is considered a transient or short-lived cell?

Mast cells Signup and view all the answers

What type of organelles are notably present in undifferentiated mesenchymal cells?

Many free ribosomes Signup and view all the answers

Where are pericytes primarily located?

Around blood capillaries Signup and view all the answers

Fibroblasts primarily originate from which cell types?

Undifferentiated mesenchymal cells and pericytes Signup and view all the answers

What is the primary function of leptin in the body?

Increase metabolic rate and decrease food intake Signup and view all the answers

Which of the following descriptions is NOT associated with reticular cells?

Central dark nucleus Signup and view all the answers

What is the key feature of macrophages in terms of their appearance under a light microscope?

Large irregular cell with a kidney-shaped nucleus Signup and view all the answers

What type of granules are associated with pigment cells?

Melanin granules Signup and view all the answers

Which of the following functions is NOT associated with macrophages?

Secretion of reticulin Signup and view all the answers

What is a key structural difference between fibroblasts and fibrocytes?

Fibroblasts have a well-developed Golgi complex, whereas fibrocytes have minimal organelles. Signup and view all the answers

Which of the following correctly describes the function of fibroblasts?

They maintain connective tissue fibers and matrix. Signup and view all the answers

How does the nucleus of a fibrocyte differ from that of a fibroblast?

Fibrocytes have a heterochromatic nucleus compared to the euchromatic nucleus of fibroblasts. Signup and view all the answers

Which type of adipocyte is characterized by multiple small fat droplets?

Multilocular Adipocyte Signup and view all the answers

Which feature distinguishes unilocular adipocytes from multilocular adipocytes?

Unilocular adipocytes have a peripheral flat nucleus. Signup and view all the answers

What characteristic is typical of the cytoplasm in young fibroblasts?

Deep basophilic Signup and view all the answers

Which function is primarily associated with multilocular adipocytes?

Thermogenesis Signup and view all the answers

What is a distinguishing feature of the organelles in fibroblasts compared to fibrocytes?

Fibroblasts have many mitochondria while fibrocytes have fewer. Signup and view all the answers

Study Notes

Connective Tissue: General Characteristics

Composed of widely spaced cells
Contains an abundant intercellular substance called matrix
Contains connective tissue fibers
Penetrated by blood vessels, lymphatic vessels, and nerves

Connective Tissue: Embryonic Origin

Originates from the mesoderm

Connective Tissue: General Functions

Connects and binds cells and organs
Provides mechanical support to tissues and organs
Divides organs into compartments
Stores fat and certain minerals
Defends against infection
Aids in wound healing and tissue repair
Acts as a medium for the exchange of metabolites between blood and tissues

Connective Tissue: Components

Cells
Matrix
- Fibers: collagen fibers, elastic fibers, reticular fibers

Connective Tissue: Types Based on Matrix Consistency

Soft: Connective tissue proper
Rubbery: Cartilage
Hard: Bone
Fluid: Blood

Connective Tissue Cells: Fixed Cells

Undifferentiated mesenchymal cells (UMCs)
- Unspecialized primitive cells
- Are a permanent source of cells in adults, found in bone marrow
- Have small, branched appearance under light microscopy (LM) with pale blue cytoplasm
- Contain a central oval pale nucleus with clear nucleoli
- Under electron microscopy (EM), they display many free ribosomes and a few other organelles
- Can differentiate into other connective tissue cells, smooth muscle cells, and endothelial cells
Pericytes
- Originate from UMCs
- Located around blood capillaries
- Appear as a small, branched cell under LM with pale blue cytoplasm
- Contain a central oval pale nucleus with clear nucleoli
- Under EM, they show many free ribosomes, few other organelles, and actin and myosin filaments
- Are adult mesenchymal stem cells
- Can differentiate into smooth muscle cells, endothelial cells, and other connective tissue cells during injury
- Can vasoconstrict capillaries
Fibroblasts and Fibrocytes
- Originate from UMCs and pericytes
- Most common cell type, present in all types of connective tissue proper
- Fibroblasts (young, immature)
  - Have many branches
  - Deep basophilic cytoplasm
  - Large pale oval nucleus
- Fibrocytes (old, mature)
  - Spindle-shaped with few processes
  - Pale basophilic cytoplasm
  - Small dark rounded nucleus
- Under EM:
  - Fibroblasts display well-developed rough endoplasmic reticulum (rER), Golgi complex, many mitochondria, and euchromatic nucleus
  - Fibrocytes exhibit few organelles, a heterochromatic nucleus
- Functions:
  - Fibroblast: synthesis of connective tissue fibers, ground substance, secretion of growth factors, activate to fibroblasts during healing
  - Fibrocyte: continuous slow turnover of fibers and matrix (maintenance), healing of connective tissue
Adipocytes (Fat Cells)
- Originate from UMCs
- Located in adipose connective tissue
- Types:
  - White adipocytes: subcutaneous, perinephric
  - Brown adipocytes: interscapular, mediastinal
- Under LM:
  - Unilocular Adipocytes: large and oval, single giant fat droplet (signet ring appearance), peripheral flat nucleus, stains orange with Sudan III
  - Multilocular Adipocytes: smaller and rounded, multiple small fat droplets, eccentric rounded nucleus, stains orange with Sudan III
- Under EM:
  - Unilocular Adipocytes: abundant smooth endoplasmic reticulum (sER), few filamentous mitochondria, single large electron-dense fat droplet
  - Multilocular Adipocytes: less developed sER, many rounded mitochondria, multiple electron-dense fat droplets
- Functions:
  - Unilocular Adipocytes: synthesis and storage of fat, organ support, heat insulation, endocrine function (leptin - increases metabolic rate and decreases food intake)
  - Multilocular Adipocytes: thermogenesis through the action of thermogenin on fat
Reticular Cells
- Originate from UMCs
- Located in the stroma of glands and organs
- Under LM: stellate cells, basophilic cytoplasm, central pale nucleus
- Under EM: variable amount of organelles, cell junctions between processes
- Functions: secrete reticular fibers, mechanical support, phagocytic activity, antigen presenting cell

Connective Tissue Cells: Free Cells

Macrophages
- Originate from blood monocytes
- Exist as fixed and free cells
- Under LM: large irregular cell, basophilic granular cytoplasm, eccentric dark kidney-shaped nucleus, can be visualized with vital stains (Indian ink)
- Under EM: irregular shape, rich in lysosomes, prominent Golgi
- Functions: phagocytic activity, form multinucleated foreign body giant cells, antigen presenting cells (APCs), destruction of old red blood cells (RBCs) in the liver and spleen
Plasma Cells
- Originate from B lymphocytes
- Located in connective tissue
- Under LM: round or oval shape, eccentric nucleus with a "clockface" appearance due to heterochromatin distribution, basophilic cytoplasm
- Function: produce antibodies
Mast Cells
- Originate from bone marrow
- Located in connective tissue
- Under LM: irregular shape, abundant granules (stain metachromatically due to heparin content), central nucleus
- Under EM: numerous granules containing histamine, heparin, and other mediators
- Functions: release histamine and other mediators involved in inflammation, allergic reactions
Leukocytes
- Migrate from the blood
- Transient cells in connective tissue
- Include: neutrophils, eosinophils, basophils, lymphocytes, monocytes
- Functions: participate in immune responses, inflammation, and wound healing

Pigment Cells

Originate from UMCs
Contain long branching processes
Under LM: small stellate cells, pale basophilic cytoplasm with scattered dark brown melanin granules
Function: carry melanin pigment granules in the dermis of the skin and the iris of the eye

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Description

Explore the essential characteristics, origins, and functions of connective tissue in this quiz. Understand its components, types based on matrix consistency, and the roles it plays in the body. Perfect for students studying biology or anatomy.