Exam 3: Lecture 10 Flashcards
What 3 ways can connective tissue be classified?
Type of matrix
Fiber density
Fiber organization
What are characteristics of connective tissue?
Few cells
Abundant matrix
Matrix contains varying protein fiber amounts
What are the major connective tissue classes?
Loose
Dense
Reticular
Elastic
What are the characteristics of Loose connective tissue?
High ratio of fibroblasts to fibrous components
Type I collagen
Found beneath epithelial tissues of most organs
What are the characteristics of Dense connective tissue?
High ratio of fibrous components to fibroblasts
Thicker bundles of collagen than loose CT
Dense irregular CT has no specific orientation
Dense regular CT has highly ordered bundles
What are the characteristics of Reticular connective tissue?
Forms stroma of spleen and lymph nodes, allows cells to be packed in between fibers
What are the characteristics of Elastic connective tissue?
Highly specialized, not found in many places in body
What are the special types of connective tissue?
Adipose
Cartilage
Bone
Hematopoietic
What are the 3 cellular components of connective tissue?
Fibroblasts/Fibrocytes
Glycosaminoglycans
Adipocytes
T/F: Fibroblasts/Fibrocytes are the least common cell in connective tissue?
False, they are the most common cell in connective tissue
What are the functions of fibroblasts/fibrocytes?
Secretion & maintenance of CT matrix
Secrete precursor fibrous molecules
Secrete amorphous components of matrix, including glycosaminoglycans
What are glycosaminoglycans?
Large, negatively charged polysaccharides consisting of repeating disaccharide units
What are the 4 groups of glycosaminoglycans?
Hyaluronic acid
Heparin/Heparan sulfate
Chondroitin/Dermatan sulfate
Keratan sulfate
Where is Hyaluronic acid found?
Cartilage, skin, synovial fluid, general CT
Where are Heparin/Heparan sulfate found?
Basement membrane, skin, lung, liver, blood vessels, mast cell granules
Where are Chondroitin/Dermatan sulfate found?
Cartilage, bone, skin, blood vessels, heart, cornea
Where is Keratan sulfate found?
Cartilage, cornea, intervertebral disks
Describe the structure of a proteoglycan
Hyauronan backbone
Linker proteins connect core proteins
Core protein has extensions of four groups of glycosaminoglycans
Core protein + glycosaminoglycans = proteoglycan
What are adipocytes?
Undifferentiated mesenchymal cells
15 times larger than normal cell
What are the 2 types of adipocytes?
White fat
Brown fat
What are characteristics of White fat?
Unicolar (one lipid droplet)
Distributed throughout body
What are characteristics of Brown fat?
Multicolar (numerous lipid droplets)
Abundant mitochondria give brown coloration
Describe collagen fiber synthesis
Begin as prepropeptide
Pre- signal sequence cleaved off after translocation into ER lumen
Pro-collagen with terminal, non-helical ends secreted into ECM
Terminal, non-helical ends cleaved to form tropocollagen
Tropocollagen spontaneously assembles into staggered arrays
T/F: Elastic fiber synthesis is the same as collagen fiber synthesis?
False, the last step is different
The pro-collagen is converted to tropoelastin instead of tropocollagen and assembles into amorphous fibers or sheets with aid of fibrillin
What are the different types of cartilage?
Hyaline
Elastic
Fibrocartilage
T/F: Hyaline cartilage is the most common.
True
What are the characteristics of Hyaline cartilage?
Avascular, type II fibers, surrounded by perichondrium, solid but flexible, chondrocytes often found in cell groups
Where is Hyaline cartilage found?
External auditory meatus, larynx, trachea, bronchi, fetal long bones, articular ends of bones
What are the 2 growth patterns of Hyaline cartilage?
Appositional-Growth on top of existing surface (non-organic things)
Interstitial-Growth by adding new material within existing material (unique to living things)
What are the characteristics of Elastic cartilage?
Addition of elastic fibers, surrounded by perichondrium, yellow b/c of elastic fibers, more opaque, flexible, & elastic than hyaline, chondrocytes located singly, type II collagen + elastic fibers
Where is Elastic cartilage found?
Auricle of ear, epiglottis
What are the characteristics of Fibrocartilage?
Increased collagen in matrix, reduced cellularity compared to hyaline, NOT surrounded by perichondrium, opaque appearance from fibrous texture, type I collagen, single sparse chondrocytes
Where is Fibrocartilage found?
Intervertebral discs, pubic symphysis, insertion of some tendons/ligaments, closely associated with dense CT or hyaline cartilage
T/F: The skeletal systems of all vertebrates begin as cartilage.
True
What are the 3 major components of cartilage formation?
Chondroblasts-Produce new matrix (top)
Chondrocytes-Maintain matrix (middle)
Lacunae-Cells within matrix (lakes)
*All are avascular
Perichondrium contains an outer _________layer and an inner _________ layer.
Fibrous
Chondrogenic
T/F: More hydroxyapatite means weaker, frailer bones.
False, increased hydroxyapatite in the matrix means stronger, more solid bones
What are the 3 types of bone?
Woven
Compact
Spongy
Where/when does woven bone occur?
During development and repair
What is another name for compact bone?
Lamellar bone
What are other names for spongy bone?
Trabecular
Cancellous
What are the characteristics of compact bone?
Dense plate on outside of long/flat bones
Concentric lamellae (Haversian) encircle central blood vessel forming an osteon (Haversian system)
Osteocytes found between lamellae connected to Haversian canal via canaliculi
Volkmann’s canals run perpendicular to Haversian canals connecting Haversian canals to each other and bone surface
What are the characteristics of spongy bone?
3-D lattic of branching, bony spicules intertwined to form trabeculae surrounding bone marrow spaces in long/flat bones
What is the macroscopic structure of bone?
Periosteum-Surrounds exterior of bone
Marrow/Medullary cavity-Inside bone
Endosteum-Lining of marrow/medullary cavity
Sharpey’s fibers-Connect periosteum to bone matrix
What are osteoprogenitor cells?
Stem cells described as bone lining cells in adult
Found in inner portion of periosteum, endosteum, & lining vascular canals of compact bone
Derived from mesenchyme of embryonic somite and possess mitotic potential
Give rise to osteoblasts
What are osteocytes derived from?
Osteoblasts and are trapped by the matrix they secrete
What are osteoclast cells derived from?
Monocyte linkage, which is derived from monocyte precursors in bone marrow
What is ARF?
Activation-resorption-reversal-formation
A cycle that occurs in adult remodeling sites and during development
What are the first 5 steps of Osteoblast/Osteoclast regulation?
1) PTH regulates bone turnover
2) Osteoblast formation stimulated by low PTH
3) Osteoclast differentiation factors stimulated from osteoblast at high PTH
4) PTH stimulates monocyte precursors to form osteoclasts
5) Elevated PTH results in erode bone & fibrosis of resulting spaces
What are steps 6-9 of Osteoblast/Osteoclast regulation?
6) PTH binds to receptors on osteoblast
7) Osteoblast stimulated to synthesize M-CSF & RANKL
8) M-CSF binds to M-CSF receptor on monocyte near by
9) Monocyte is no macrophage and expresses RANK
What are steps 10-13 of Osteoblast/Osteoclast regulation?
10) RANK binds to RANKL making macrophage multinucleated immature osteoclast
11) Osteoblast secretes osteoprotegerin
12) Non-functional osteoclast uncouples from osteoblast and becomes functional osteoclast
13) Calcitonin acts to reduce bone resorption
