Connective tissue

Question 1

What is connective tissue and how is it characterized

Answer 1

Connective tissue is a type of tissue in the body that is characterized by a copious extracellular (intercellular) matrix. It is composed of different cell types within differing extracellular matrices, and the cell and tissue type varies dependent on function.

Question 2

What are the two key functions of connective tissue?

Answer 2

The two key functions of connective tissue are binding tissues together and providing support.

Question 3

What are the different types of connective tissue?

Answer 3

The different types of connective tissue include connective tissue proper, cartilage, bone, and blood.

Question 4

What are the main examples of connective tissue cells?

Answer 4

The main examples of connective tissue cells are derived from the same cell lineage, embryonic mesenchyme cells. They include adipocytes (fat cells), fibroblasts and fibrocytes (fibre cells), chondroblasts and chondrocytes (cartilage cells), osteoblasts and osteocytes (bone cells), and blood cells.

Question 5

What is the extracellular matrix and how does it vary with tissue and cell type?

Answer 5

The extracellular matrix is a collection of extracellular molecules secreted by cells that provides structural and biochemical support to the surrounding cells. It varies with tissue and cell type, with main examples including fibres (fibro, hyaline, and elastic), chondroitin sulphate matrix (with and without fibres, found in cartilage), bone matrix (calcium salt-based), and fluid (plasma).

Question 6

What are the different types of connective tissue?

Answer 6

Connective tissue can be generally classified as areolar (loose connective tissue), adipose, or fibrous.

Question 7

What is areolar tissue and where is it distributed in the body?

Answer 7

Areolar tissue is a loose connective tissue that is the most generalized of all connective tissue types. It is primarily used for packing and supportive functions, and is distributed under the skin (dermis), around blood vessels and nerves, between muscles, and within the digestive tract (submucosa).

Question 8

What is areolar tissue composed of and what types of cells are found in it?

Answer 8

Areolar tissue is composed mainly of gelatinous material (hyaluronic acid) and a few fibres. Cells found in areolar tissue include mast cells (which contain 5-hydroxytryptamine and histamine and are involved in inflammation), macrophages (which are phagocytic and can be fixed or mobile), and some adipocytes and fibroblasts.

Question 9

What are the functions of adipose tissue?

Answer 9

Energy reservoir, insulation, endocrine (hormones such as leptin)

Question 10

Where is adipose tissue distributed in the body?

Answer 10

Under the skin (subcutaneous layer), around the heart (epicardial), and kidneys (perinephric)

Question 11

What is fibrous tissue composed of?

Answer 11

Fibroblasts and two main fiber types: collagen (white fiber) and elastic (yellow fiber)

Question 12

What is the function of collagen fibers in fibrous tissue?

Answer 12

Collagen fibers provide strength and support, resist tension and compression, and are arranged in bundles. They are found in tendons, ligaments, and capsules of many organs.

Question 13

What is the function of elastic fibers in fibrous tissue?

Answer 13

Elastic fibers are thicker and elastic, and are found in structures that need to be highly bendable, such as the middle wall of arteries (tunica media).

Question 14

What is cartilage?

Answer 14

Cartilage is a firm, flexible connective tissue that is abundant in extracellular matrix and contains collagen and/or elastin fibers, proteoglycan, and chondrocytes. It is avascular, aneural, and alymphatic.

Question 15

What are the three types of cartilage and what are their characteristics?

Answer 15

Hyaline cartilage is flexible and resilient, elastic cartilage is highly bendable, and fibrocartilage resists compression and tension.

Question 16

What is the most common form of degenerative joint disease and what causes it?

Answer 16

Osteoarthritis is the most common form of degenerative joint disease and is caused by the failure of hyaline cartilage to protect the underlying bone from mechanical forces.

Question 17

What is the composition of bone extracellular matrix?

Answer 17

Bone extracellular matrix is ~20% water and ~80% solid matrix, which is composed of ~30% organic matrix (collagen, proteoglycan, and non-collagen molecules) and ~70% inorganic salts (mainly calcium and phosphate as hydroxyapatite crystals).

Question 18

What are the Haversian systems (osteons) in cortical bone?

Answer 18

Haversian systems are composed of concentric rings of lamellae, Haversian canals (which contain nerves, blood, and lymph vessels), and lacunae with osteocytes. Canaliculi links the lacunae with the Haversian canals.

Question 19

What are the bone cells and what are their functions?

Answer 19

Osteoblasts secrete organic matrix and remove calcium and phosphate from the blood to play a vital role in calcification and ossification. Osteocytes sense mechanical stress and regulate bone remodeling. Osteoclasts remove/clean away bone tissue to form bone cavities, secrete lysosomal enzymes to digest bone matrix, and produce metabolic acids to convert insoluble calcium into soluble organic calcium that enters the blood.

Question 20

What is the string and balloon model in hyaline cartilage biochemistry?

Answer 20

The string and balloon model explains how the high fixed negative charge in GAG molecules in hyaline cartilage increases cation concentration, increases solution osmolarity, and swells the GAG molecules. The swelling is resisted by the collagen network, creating a string and balloon model.