Connective Tissue Flashcards
Function of Connective Tissue
- Structure
- Defense and protection
- Nutrition
- Fat deposit for cushioning, insulation, and energy reserves
Where does connective tissue derive from
mesoderm and neural crest from ectoderm
Chondroblasts
responsible for synthesis and elaboration of the ECM’s associated cartilage
Osteoblast
synthesis and elaboration of bone
Where do undifferentiated mesenchymal cells come from
mesoderm and in some ares of the body can also come from neural crest cells from ectoderm
Function of active fibroblasts
synthesize and elaborate components of ECM
Organelles of active fibroblasts
- euchromatic nucleus
- large column of rER and thus also a basophilic cytoplasm
- Well-developed golgi apparatus seen proximate to the nucleus
- Mitochondria to supply fuel for protein synthesis
Inactive fibroblasts are also called
quiescent or fibrocyte
Organelles of inactive fibroblasts
- decreased rER
- less elaborate golgi
- slender nucleus and condensed chromatin
- more eosinophilic cytoplasm
Cortisol
has putative antifibrotic activities including inhibition of fibroblast growth and deposition of collagen
-Prolonged administration can lead to decrease in bone
Why do active fibroblasts have increased activity
due to need to synthesize extracellular material for wound healing. Greater capacity to divide during wound healing
What happens if you are defienct in vitamin C
hydroxylation step is compromised, get decreased collagen synthesis - scurvy
Procollagen peptidases
Will enzymatically cleave the propeptides to make the molecules less soluble so they can assemble.
Extensions of helix
propeptides on each end, which maintain the solubility of this structure and can be processed internally by fibroblast
Myofibroblasts
- Possess characteristics of fibroblasts and smooth muscle cells
- Has actin and myosin (so they have contracile activity)
- become more numerous in wound healing
Dupuytren’s contracture
- Palmar aponeurosis, a triangular shaped collagenous structure in palm of hand
- Repair of microvascular ischemia in tissue leads to active myofibroblast and fibroblasts
- Increased elaboration of type III collagen, which forms cross links with myofibroblasts, leading to contractions of 4th and 5th digits
White adipocytes
- look like empty spaces, tissue processing removes the lipid droplet, leaving a signet ring appearance
- Nucleus pushed out to periphery
Apidocytes
synthesize leptin, thus have endocrine function
Leptin
works to suppress appetite by signaling decrease in caloric intake
-mutation leads to morbid obesity
Lipdystrophies
- can be acquired or due to genetic defect
- loss of body fat may be general or confined to specific body regions
Brown adipocytes
- multilocular
- nucleus is centrally located
- peripherally located cytoplasm, which is acidophilic due to large column of mitochondria
- cancer of brown adipose tissue is rare but possible
Functions of brown adipose tissue
produce heat, especially in newborns to regulate body temperature
Why do infants need brown fat
- they can’t shiver
- ATP synthesis capability is uncoupled so we use mitochondrial steps to produce heat rather than to synthesize ATP
Do adults have brown fat?
Yes, some. Can be seen by putting them in a cold environment then imaging
Mast cell
has metachromatic granules.
What happens when antibody antigen complex binds to RC receptor on cell surface of mast cell
- cell massively releases its contents
- leads to increased mucous, vasodilation, and bronchospasms due to leukotrienes.
Macrophage
- derived from monocyte
- centrally located nucleus with an indentation, well developed rER and golgi complex primarily to form lysosomes
What types of phagocytic cells are derived from a monocyte
microglia, Kupffer cells in liver, alveolar macrophages in lug, and osteoclasts in blood
Giant Cells
-macrophages fuse together in states of chronic inflammation
Migratory cells
migrate into CT from blood
Plasma cell
- Basophilia
- Large negative Golgi
- Clock face nucleus
- antibodies are secreted via the constitutive pathway
2 waves of leukocytes in response to cardiac injury
- 1st wave - neutrophils
- 2nd wave - monocytes (~2 days after damage)
Function of neutrophils
clean up and remove damaged tissue
Classifications of Connective Tissue
embryonic, proper, and specialized
2 subclasses of embryonic
mesenchymal and mucus
CT proper has 2 subclasses
loose or dense
dense connective tissue
arranged in irregular or regular pattern
specialized connective tissue types
- adipose
- reticular
- cartilage
- bone
- blood
Mesenchymal connective tissue
- least differentiated
- large amount of ECM materials, including group substance and type 3 reticular fibers
Mucous connective tissue
- found in wharton’s jelly in umbilical cord
- Expansion of ECM and fibroblasts where type I and III collagen are being formed
Loose connective tissue
- abundant, viscous, amorphous with hyaluronic acid, GAGs, proteoglycans, and glycoproteins
- lies immediately deep to epithelium and surrounds blood vessels
Cells present in loos connective tissue
fibroblasts, macrophages, adipose cells, mast cells, and undifferentiated cells
Dense regular collagenous connective tissue
- type I collagen fibers (acidophilic) densely arrayed in parallel
- elongated, basophilic nuclei of fibroblasts
- ex) tendons and ligaments
Ligaments
- fibers less regularly arranged, higher % of ground substance, and a greater mixture of elastic fibers
- constitute of dense cartilaginous tissue
- greater degree of stretch due to elastic fibers
Mucoid degeneration of anterior cruciate liagment
- pt presents with knee pain or restricted movement
- in the MRI, ACL has celery stalk appearance
- treatment usually not needed
Dense regular connective tissue of elastic fibers
- sparse, viscous, amorphous with hyaluronic acid, GAGs, proteoglycans, and glycoproteins
- Elastin forms thin sheets of fenestrated membranes. -Elastic fibers branch and run parallel to one another
- has fibroblasts
- located in: ligamenta flava, supensory ligament of penis, vocal ligament, and arteries
Elastin
forms lamellae and laminae in blood vessels
Dense irregular connective tissue
- Sparse, viscous, amorphous with hyaluronic acid, GAGs, proteoglycans, and glycoproteins
- Tightly packed, type I collagen fibers oriented in many axes. Elastic fibers are interspersed (and darker in color).
- Scattered fibroblasts
- Location: Organ capsules, dermis of skin. and sleeve around nerves
Ehlers-Danlos
- Defect in type I collagen
- Presents with hyperelasticity of skin, hypermobility of joints
Elastic tissue in dermis is susceptible to what
UV damage
Reticular tissue in liver
- Little ground substance
- Reticular fibers (type III collagen)
- Reticulocytes and other cell types
- Location: Red bone marrow, liver, and lymphatic tissues/organs
Adipose connective tissue
- Spare ground substance
- Reticular fibers are found between adipocytes
- Adipocytes
- Subcutaneous areas, abdominal cavity
- Thin layers of cytoplasm, empty-looking cells
