Connective Tissue and Stem Cells Overview

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Questions and Answers

What is the primary origin of muscle tissue in the embryo?

Mesenchymal stem cells (MSC) (correct)

Neural stem cells (NSC)

Hematopoietic stem cells (PHSC)

Adipose tissue

Which type of tissue retains tissue-specific stem cells in adults?

Skeletal muscle (correct)

Adipose tissue

Cardiac muscle

Epithelial tissue

Which of the following statements is true regarding adult adipocytes?

They continuously divide throughout adulthood.

They are derived from hematopoietic stem cells.

They change their volume based on lipid storage. (correct)

They can trans-differentiate into muscle cells.

What role does UCP-1 play in fat metabolism?

It determines the thermogenic potential of fat. Signup and view all the answers

What process allows a differentiated cell to revert to a stem-like state?

De-differentiation Signup and view all the answers

Which collagen type is primarily found in hyaline cartilage?

Type II collagen Signup and view all the answers

What characteristic is unique to muscle progenitors during embryonic development?

They elaborate within connective tissue compartments. Signup and view all the answers

Which stem cell type is not considered to exist in humans based on the information provided?

Embryonic stem cell Signup and view all the answers

What is the main distinction between brown fat and white fat?

Brown fat is formed from a different lineage than white fat. Signup and view all the answers

What type of collagen serves as a scaffold in the initial formation of bone?

Type X collagen Signup and view all the answers

Which type of stem cell is responsible for generating adipose tissue?

Mesenchymal stem cells (MSC) Signup and view all the answers

Which cells are derived from MSC in the context of cartilage formation?

Osteocytes and chondrocytes Signup and view all the answers

What is the main clinical application of F-18 FDG PET imaging mentioned in the context?

Metastasis detection in melanoma Signup and view all the answers

What kind of fibers must be present to produce elastic cartilage?

Elastic fibers only Signup and view all the answers

What is the characteristic of the interface between bone and cartilage?

They are connected by a fibrous periosteum or perichondrium. Signup and view all the answers

What is a primary function of proteoglycans in cartilage?

To resist compression Signup and view all the answers

What is synonymous with 'basal lamina'?

Basement membrane Signup and view all the answers

What role do proteoglycans play in the extracellular matrix?

They provide weak bonding sites for water Signup and view all the answers

What happens to proteoglycans in standard preparations?

They are not normally visible Signup and view all the answers

What is a function of perineuronal nets (PNNs) in the brain?

To guide developing axons' connections Signup and view all the answers

What effect does the disruption of PNNs by chondroitinase have?

It restores plasticity in a visual system model Signup and view all the answers

What is the primary characteristic of ground substance in the extracellular matrix?

It is not preserved in standard preparations Signup and view all the answers

Which of the following is true regarding proteoglycans?

They consist of very large molecules Signup and view all the answers

What common misconception might people have about basement membrane?

It is only found in epithelial tissues Signup and view all the answers

What is true about blood in relation to connective tissue (CT)?

Blood is a type of connective tissue with high cellularity. Signup and view all the answers

What is the function of cytokines in the immune response?

They control the cellular response. Signup and view all the answers

Which of the following cells is primarily involved in innate immunity?

Macrophage Signup and view all the answers

In insects, what is the role of hemolymph?

To circulate nutrients and waste. Signup and view all the answers

What type of immune response do T-lymphocytes specifically target?

Intracellular pathogens Signup and view all the answers

What is a characteristic of the ground substance in connective tissue?

It consists of plasma and modified interstitial fluid. Signup and view all the answers

Which type of fat is classified under adipocytes?

Brown fat is multilocular. Signup and view all the answers

What type of fiber is normally absent in connective tissue but can be present in certain conditions?

Fibrin Signup and view all the answers

What type of collagen fibers is characterized as small and includes reticular fibers?

Type III Signup and view all the answers

Which type of collagen is a major structural component that contributes to the creation of fibrillar structures?

Type I Signup and view all the answers

At what stage does the assembly of Type I collagen occur according to the information provided?

Extracellularly Signup and view all the answers

What characteristic feature can help to differentiate between areas dominated by Type I or Type III collagen?

Density of collagen fibrils Signup and view all the answers

Which type of collagen is specifically mentioned as being non-fibrillar and consists of many others?

Type IV Signup and view all the answers

In terms of morphology, what distinctive feature do collagen fibers show under high-magnification electron microscopy?

Banding characteristic specific to their structure Signup and view all the answers

Which type of collagen is known for its role in forming a meshwork structure?

Type IV Signup and view all the answers

Which types of collagen are described as the structural, 'rope-like' collagens?

Type I and Type III Signup and view all the answers

Study Notes

Connective Tissue Definition

Connective Tissue (CT) is a type of tissue that connects and supports other tissues in the body.
It's derived from Mesenchymal Stem Cells (MSCs)

Trans-differentiation

MSCs can trans-differentiate into various cell types including adipocytes, muscle, myeloid, lymphoid, fibroblasts, red blood cells (RBCs), and granulocytes.
This process involves a change in cell type without going back to an embryonic stem cell.

De-differentiation

MSCs can de-differentiate towards an embryonic stem cell state, but this process is not known to occur in humans.

Muscle Tissue

Muscle tissue originates from MSCs.
Muscle progenitors form during embryonic and fetal development.
Smooth and skeletal muscle retain tissue-specific stem cells in adults, but cardiac muscle likely does not.

Adipose Tissue

Adipose tissue is a specialized type of CT.
Adult adipocytes (fat cells) do not divide but change their volume by storing lipids.
Adipose tissue can be classified as white fat, beige fat, or brown fat.

Thermogenic Fat

Uncoupling protein 1 (UCP-1) in mitochondria determines whether fat is thermogenic, converting mitochondrial respiration products from ATP to heat.

Adipose Lineage

White fat may be interconvertible with beige fat.
Brown fat is a separate lineage.

Special CTs - Bone & Cartilage

Progenitor cells for bone and cartilage are derived from MSCs: osteoprogenitors and chondroprogenitors.
Cells: bone has osteocytes and cartilage has chondrocytes.
Fibers: Bone is composed of mineralized type I collagen, with type X collagen used as a scaffold initially. Cartilage is primarily type II collagen, with type I collagen in fibrocartilage and elastic fibers in elastic cartilage.
Ground Substance: Cartilage has many proteoglycans, which resist compression.
Interface: Bone and cartilage are always bounded by a collagen sheet (fibrous periosteum or perichondrium) that functions as the mechanical structure of the joint capsule.

Blood

Blood is highly cellular and considered a distinct compartment in humans, separate from connective tissue.
Humans lack fibers in blood (except for fibrin).
Blood's ground substance is plasma.
Unlike connective tissue, blood is not derived from MSCs.

Insect Blood

Insects have hemolymph that circulates in the hemocoel compartment, where blood and interstitial fluid are identical.

Resident Cells from MSCs

Fibroblasts: These cells can be precursors, general fibroblasts, location-specific types, or activated types (myofibroblasts).
Adipocytes: Composed of white fat (unilocular), beige fat, or brown fat (multilocular).

Cells of the Immune System

Immune system cells are derived from the hematopoietic stem cell (HSC).
Innate Immunity: Macrophages (often resident in tissue), neutrophils (1st cellular response and chemotaxis), mast cells (enhancing leukocyte response through inflammation), eosinophils (inflammatory response), and basophils.
Adaptive Immunity: B-lymphocytes and plasma cells (response to extracellular pathogens), T-lymphocytes (response to viruses, intracellular pathogens).

Cytokines and Antibodies

Cytokines regulate cellular response, with inflammatory cytokines (Il-1, TNF-alpha, Il-6) driving migration and diapedesis of leukocytes. Anti-inflammatory cytokines (Il-4, Il-6, Il-10, Il-11, Il-13) also play a role.
Antibodies control inflammation, with mast cells responsive to allergens (IgE) and plasma cells producing antibodies specific to the environment (IgM, IgG, IgE, IgA, IgD).

Collagen Fibers

Collagen fibers are identifiable under electron microscopy (EM).
Fibrillar anchoring type VII and meshwork type IV are key types of collagen fibers.
Collagen fibers can be categorized into three types:
- Type I: Large, structural collagen, responsible for strength.
- Type III: Smaller, provides flexibility and structure.
- Type IV: Present in basement membranes, acts as a scaffold.

Type I Collagen Assembly

Type I collagen assembly is completed extracellularly.
Type I collagen fibrils aggregate as their density increases.
Type III collagen does not undergo the same aggregation process as type I.

Type I & III Collagen Microscopic Appearance

Type I and Type III collagen are both structural, "rope-like" collagens.
The relative abundance of each type can be distinguished under microscopy.

Basal Lamina & Basement Membrane

"Basal lamina" (from EM) and "basement membrane" are synonymous terms referring to the thin layer that surrounds epithelial cells and muscle fibers.

Proteoglycans

Proteoglycans are large molecules that hydrate the extracellular matrix by providing negatively charged regions that weakly bond with water (H2O).
Proteoglycans are difficult to visualize in standard preparations.

Proteoglycans in the Brain

Proteoglycans in the brain form perineuronal nets (PNNs) that surround neurons.
PNNs are thought to influence neuronal plasticity and stability.
Disrupting PNNs with chondroitinase can restore plasticity.

Component Imbalance

Imbalance in the components of connective tissue can lead to various disorders.

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Description

This quiz covers key concepts related to connective tissue, including its definition, the role of mesenchymal stem cells, and the processes of trans-differentiation and de-differentiation. It also explores the origins of muscle and adipose tissues and their specific characteristics. Test your knowledge on these essential aspects of human biology.