Week 5: Connective Tissue

Question 1

What are the three divisions of connective tissue?

Answer 1

Normal

Spinal

Supportive

Question 2

What can normal connective tissue become?

Answer 2

Loose CT (lamina propria), dense regular CT (ligaments, tendons), and dense irregular CT (dermis)

Question 3

What kinds of CT can special CT become?

Answer 3

Adipose

Elastic

Hematopoietic (lymphoid and myeloid)

Mucous (lining of respiratory, GI, and reproductive tracts)

Question 4

What kinds of tissue can supportive CT become?

Answer 4

Cartilage

Bone

Question 5

What are the non-bloodborne cells that the hematopoietic line can form?

Answer 5

MOL:

Microglia, a CNS-based type of macrophage

Osteoclasts, which are a form of bone-based macrophage (degrade bone tissue)

Langerhans’ cells, found in the stratum spinosum, help phagocytose dead cell materials and waste in the epithelium

Question 6

What are the kinds of cells that stem from the mesenchymal origin? How do you remember this?

Answer 6

Fibroblasts, adipocytes, chondrocytes, osteoblasts, mesothelial, epithelial, and smooth muscle cells

(FA COMES)

Question 7

What are the two major extracellular components of connective tissue?

Answer 7

Amorphous and fibrous components

Question 8

What are the two types of main materials that make up connective tissue? How do they relate to one another?

Answer 8

Cell components and extracellular (amorphous and fibrous) components

Cell components secrete the extracellular components

Question 9

What is the structure and what are the histological characteristics of fibroblasts?

Answer 9

They are structural (produce fibers/ground substance)

They have distinctly blue nuclei (H&E stain), and filiform cytoplasm that secretes fibrous components

Question 10

What is the function and the histological characteristics of adipocytes?

Answer 10

They store energy in the form of TAGs

They can be unilocular (one large lipid droplet) or multilocular (many lipid droplets in each cell)–each small blob seen is a lipid droplet. Nuclei of unilocular cells is squeezed off to the side.

Multilocular cells are mainly found in brown fat in infants–more SA than one large droplet, allows for rapid conversion of energy.

Question 11

What are the functions and histological characteristics of macrophages?

Answer 11

Macrophages phagocytose cells via endocytotic processes, using nitric oxide and other chemicals to kill pathogens

On slides, macrophages will ingest dye, giving them a splotchy-looking appearance

Question 12

What are the functions and histological features of plasma cells?

Answer 12

Plasma cells produce antibodies for the immune system. This is a type of B cell.

Plasma cells have a large, eccentric nucleus, a cartwheel arrangement of heterochromatin, and abundant Golgi and ER needed to produce IgGs

Question 13

What are the functions and histological features of mast cells?

Answer 13

Mast cells are essentially basophils that mature once they reach a target tissue, rather than emerging from tissue fully formed. If mast cells recognize an antigen, IgEs dimerize and trigger an intracellular signal that releases histamine and heparin (inflammatory signaling molecules).

They have large, black hole-like vacuoles

Question 14

What is the amorphous component of CT mostly composed of?

Answer 14

Glycosaminoglycans (GAGs like hyaluronic acid)

proteoglycans (proteoglycan aggregates like aggrecan, have a bottlebrush-like appearance)

glycoproteins (cell binding proteins like integrin, fibronectin, and laminin)

Question 15

What is the fibrous component of CT mostly composed of?

Answer 15

Collagen fibers - 20+ kinds, adhere cells and tissues, form the skeleton, protective dermis and acts as messenger substrate

Question 16

What are the principal steps in collagen synthesis?

Answer 16

Preprocollagen = Alpha chain formation with signal peptide

Procollagen = Alpha chain moves through RER, where signal peptide is cleaved, and into ER, where procollagen is partially glycosylated

Moves into Golgi apparatus, is further glycosylated and processed

Secreted from trans Golgi complex as a triple helix structure

Pro collagen peptidase cleaves registration peptide, forming the much less soluble tropocollagen, which moves out of the cell

Covalent crosslinks form between collagen molecules, catalyzed by lysyl oxidase, an enzyme that uses Vitamin C as a cofactor

Question 17

What kinds of diseases arise from collagen deficiency or genetic mutations to DNA that produces collagen-manufacturing enzymes? What are their symptoms?

Answer 17

Ehlers-Danlos - aortic/intestinal rupture, high skin eleasticity, eyeball rupture, increased articular mobility, frequent luxation (displacement of joints)

Scurvy - lack of Vitamin C, a cofactor for lysyl oxidase and faulty crosslinking of collagen fibers, causes ulceration of gums and mouth, and hemorrages

Osteogenesis imperfecta - point mutation in Ala –> Gly, causes brittle bones and cardiac insufficiencies

Question 18

What are the two main components of elastic fibers, and what do each of them do?

Answer 18

Fibrillin (oxytalan) that resist tension (like the meshwork of metal grating in cement)

and

Elastin deposits, which can form elaunin (less elastin deposited) or elastic fibers (more elastin deposits)

Question 19

What is a clinical issue that arises due to the disfunction of elastic fibers?

Answer 19

Marfan syndrome is a mutation in the fibrillin gene, and causes dysfunctional elastic fibers. This can lead to aortic rupture due to the aorta not being able to withstand the force from highly pressurized blood leaving the heart.

Question 20

What are the functions and histological characteristics of reticular fibers?

Answer 20

Reticular fibers or Type III collagen fibers are enriched in lymphoid organs and tissues, and stain black with a silver stain–have a smaller diameter than collagen fibers.