Connective Tissue

Question 1

What is connective tissue?

Answer 1

Connect other tissues and provides a framework and support

• Originates in mesoderm;
• composed of 3 components: cells (slender fibroblast cells will be most obvious), fibers, and amorphous ground substance
• Highly vascularized

Question 2

Function of connective tissue

Answer 2

• Helps in defense mechanism and acts as a reservoir of hormones and cytokines
• Assists in growth, development, repair, and storage

Question 3

Types of connective tissue

Answer 3

1. Embryonic connective tissue
2. Adult connective tissue
3. Specialized connective tissue

Question 4

Embryonic connective tissue and its composition

Answer 4

• present primarily in embryo, and give rise to adult connective tissue including blood
• Composed of Irregularly shaped Mesenchymal cells and mucous/gelatinous tissue

Question 5

Mucous/Gelatinous connective tissue of embryonic CT

Answer 5

• Also known as Wharton’s Jelly (in the umbilical cord)
• Contains stellate fibroblasts and viscous, gel-like ground substance that contains collagen and proteoglycans

Question 6

Adult connective tissue and its types

Answer 6

In adult organisms, classified based on composition/abundance of cells/materials.

Types:
1. loose connective tissue
2. dense connective tissue
3. elastic connective tissue
4. reticular connective tissue
5. adipose tissue

Question 7

loose connective tissue

Answer 7

• Most widely found in adult animals
• Composed of both resident and wandering cells
• Has more cells than dense, a lot less fibers
• All three fibers present
• Primarily found beneath the epithelia that cover body cavities, and in areas where foreign particles come in contact with tissues

Eg. Lamina propria, underneath the respiratory and gastrointestinal epithelium is loose connective tissue with large number of immune cells

Question 8

Dense connective tissue

Answer 8

• regular or irregular based on how fibres are arranged; if random then irregular
• Has less cell nuclei and a lot of fibers

Question 9

Elastic connective tissue

Answer 9

Elastic fibres are most abundant in this tissue type

Question 10

Reticular connective tissue

Answer 10

Reticular network/ fibres are most abundant in this tissue

Ex. lymph nodes

Question 11

Specialized connective tissue

Answer 11

Tissue includes cartilage, bone, blood, lymphatic tissue

Question 12

Components of connective tissue

Answer 12

1. cells
2. fibers
3. ground substance

Question 13

Cell types in connective tissue

Answer 13

1. Resident cells
2. Wandering cells

Question 14

Resident cells

Answer 14

• Relatively stable, move less/exhibit no movement

Eg. Fibroblasts, myofibroblasts, macrophages, adipose cells, mast cells, mesenchymal stem cells

Question 15

Wandering Cells

Answer 15

Cells that have migrated to the tissue from the blood in response to a specific stimuli

Question 16

Fiber types in connective tissue

Answer 16

Present in varying amounts, produced by fibroblast, proteins made of long peptide chains

Types:
1. Collagen fibers
2. Reticular fibers
3. Elastic fibers

Also can contain 2 types of fibrous adhesive proteins that bind structural fibers together and form the matrix

Question 17

Types of fibrous adhesive proteins present in connective tissue

Answer 17

1. Fibronectin
2. Laminin

Question 18

Collagen fibers

Answer 18

Principal fiber in connective tissue, made of collagen (over 27 types), most abundant, provides tensile strength

Question 19

Reticular fibers

Answer 19

Forms a network around muscle, nerve, adipose tissue, and forms a main part of the basement membrane. Individual type I collagen

Question 20

Elastic fibers

Answer 20

High levels of elastin

Fibers must be able to stretch/deform under stress and then return back to their original state

Question 21

Ground substance within connective tissue

Answer 21

A part of the extracellular matrix, which forms a structural support that surrounds the connective tissue cells. The other main component of the ECM are fibers made of collagen and elastin

• Cells and fibers are embedded in an amorphous ground tissue
• Contains glycosaminoglycans, proteoglycans, plasma constituents, metabolites, water and ions
• Very high water content so ground substance is a hydrated gel

Question 22

Loose connective tissue

Answer 22

• Most widely found in adult animals
• Composed of both resident and wandering cells
• Cells are more abundant, less fibers
• All 3 fiber types present
• Primarily found beneath the epithelia that cover body cavities, and in areas where foreign particles come in contact with tissues

Eg. Lamina propria- underneath the respiratory and gastrointestinal epithelium is loose connective tissue with large number of immune cells

Question 23

Dense connective tissues

Answer 23

More fibers and ground substance than cells

Two types
1. Dense irregular= random orientation of collagen fiber bundles
- Found in gastrointestinal tract, pleura, spleen, liver, kidney, testis etc.

2. Dense regular= fibers oriented in a regular pattern/same direction.
   - Found in collagenous tendons and ligaments

Question 24

Elastic Connective tissue

Answer 24

Abundance of elastic fibers that branch and interconnect. The fibers are surrounded by loose connective tissue

Eg. Elastic ligaments

Question 25

Reticular connective tissue

Answer 25

Composed of stellate reticular cells and complex 3D network of reticular fibers

Eg. Stroma of lymphatic organs including spleen, lymph node, thymus

Question 26

Adipose Tissue types

Answer 26

Two types:
1. White adipose tissue (WAT)

2. Brown adipose tissue (BAT)

Question 27

White adipose tissue

Answer 27

• Unilocular adipocytes/fat cells
• Surrounded by fibrocytes, collagen and reticular fibers
• Lipid storage, and hormone and cytokine production

Question 28

Brown Adipose Tissue

Answer 28

• Multiocular adipocytes
• Storage and energy production
• Present mainly in the thoracic cavity, and also seen around large blood vessels in the abdominal cavity