Connective Tissue Flashcards
how does the ratio of cells to ECM compare in epithelium vs connective?
connective tissue (stroma) has relatively few cells, large amount of intercellular material (ECM)
what are the 2 components of the ECM (histology)
fibers (collagen, elastin) and ground substance (ex, proteoglycans)
what cell of connective tissue produces BOTH fibers and ground substance
fibroblast
superficial fascia is made of
loose irregular connective
tendons and ligaments are made of
dense regular connective
tendons vs ligaments
tendons: muscle to bone, mostly collagen (don’t want tendons to stretch)
ligaments: bone to bone, more elastic fibers (want ability to return to original shape)
where are reticular fibers found?
endomysium (surrounding individual myocytes), endoneurium (nerve fibers), support lymphoid tissue
fine fibers
the _____ properties of ground substance in loose connective tissue enable it to resist compression
polyanionic properties - abundance of negatively charged molecules, enable ground substance to hold in Na+ and water to resist compression
the hypodermis is what kind of connective tissue
superficial fascia, loose (areolar) connective tissue
functions mostly as packing material
usually in sheathes surrounding skeletal muscles from their origins to insertions, or in sheets partitioning skeletal muscles, these tissues are involved in force transmission. What is this type?
deep fascia - dense, fibrous connective tissue
function of superficial fascia vs deep fascia
superficial fascia - packing material
deep fascia - involved in force transmission and venous return (in lower extremities)
how does turnover of dead components of connective tissue, fibers, and ground substance occur?
components are degraded by macrophages, replaced by fibroblasts (slowly, so healing of tendons and ligaments takes time)
fibroblasts and mesenchymal cells have great capacity to proliferate in response to injury
what are the physical/cellular features of fibroblasts (fibrocytes)
produces components of ECM (BOTH fibers and ground substance)
- well-developed RER and Golgi
- fusiform, long, tapered
- central nucleus, prominent nucleolus
how do identify mesenchymal cell in EM
undifferentiated cell that retains potential to develop into fibroblasts, smooth muscle cell, adipocytes, others
large nucleus with scant cytoplasm
it’s the cell that doesn’t really look like anything (can’t really see any organelles)
appearance of white vs brown adipose tissue
white: energy storage and protection, one large fat droplet inclusion
brown: thermogenesis and energy consumption, lots of mitochondria and multiple small fat droplet inclusions
diapedisis =
extravasation
WBC moves through endothelium to enter connective tissue
role of macrophage
begin as monocyte, becomes macrophage once it leaves bloodstream and enters connective tissue
functions: phagocytosis, APC (antigen presenting), forms mononuclear phagocyte system
organ specific forms: Kupffer (liver), alveolar dust cells (lungs), microglia (brain), etc
what do mast cells contain
secretory granules contains vasoactive substances (histamine)
*if it’s got granules you can see, it’s a mast cell (all other granulocytes have granules that are too small to see)
large collections of lymphocytes are found in the ______ of the respiratory and GI tract
lamina propria - sub-epithelial connective tissue
*lymphocytes appear as mostly nucleus with a little bit of cytoplasm
B lymphocytes are stimulated to become _____, which produce antibodies
plasma cells
in LM, have basophilic cytoplasm (RER), lightly stained Golgi, snowflake shaped heterochromatin in nucleus
function of eosinophils and appearance in imaging
phagocytosis in response to parasitic infections
LM: stain bright orange-red with eosin when in circulation, nucleus has 2-3 lobes
EM: granules have hamburger or football shape
function and appearance of neutrophils
“first responders” of inflammation, function in phagocytosis, exude cellular compartments to form NETS (neutrophil extracellular traps) to engulf microbes
nucleus has 3-5 lobes, small cytoplasmic granules
match:
cornea or dermis
dense regular or irregular connective tissue
corner - regular dense connective
dermis - irregular dense connective
what type of collagen is found in reticular fibers
type III
____ are found in wall of arteries
elastic fibers (why artery walls look squiggly)
how does cartilage become bone
TRICK question: cartilage does NOT become bone, it is REPLACED by bone
if matrix of cartilage calcifies, cells are cut off form nutrient (by diffusion) and die
3 types of cartilage
hyaline: end of long bones, end of ribs, nose
elastic: where return to shape after stretching is important (ex - epiglottis, external ear)
fibrocartilage: where strength is important (intervertebral discs, meniscus of knee, disc of temporomandibular joint)
chondroblasts (immature chondrocytes) produce ECM and eventually settle to reside in _____
chondroblasts are known as chondrocytes once they are surrounded by ECM and reside in lacuna
ECM of cartilage is composed of ______ which draws water and makes it resistant to compression
cartilage proteoglycan GAGs make gourd substance polyanionic - negatively charged, which attracts Na+ and after follows
liquids cannot be compressed, making cartilage resistant
explain the 2 ways cartilage can grow
- appositional growth: at periphery (chondrogenic cells divide)
- interstitial growth: at interior of cartilage (chondrocytes divide)
*however, cartilage is nourished by diffusion so growth is limited
what important ions are found in bone
Calcium (most of body’s Ca2+ is in bone), PO4-
compact vs spongy bone
compact/dense/cortical bone: outer weight-bearing portion (makes up most of appendicular/limb skeleton), mostly calcified
spongy/cancellous/trabecular bone: honeycomb shaped trabeculae, forms inner regino of bones, contains bone marrow (axial skeleton - ribs and vertebrae - has higher proportion)
what kind of bone has trabeculae
spongy/trabecular/cancellous
axial skeleton (ribs and vertebrae) has proportionally more than appendicular skeleton (limbs)
when calcium is mobilized it comes from _____ bone first
cancellous/compact/dense bone
what is the structure of long bone (top to bottom)
epiphysis at ends (closed epiphyseal growth plate)
spongy (cancellous bone) at metaphysis (inside epiphysis)
diaphysis (shaft) has compact bone and marrow cavity
periosteum
outer fibrous layer
inner cellular layer - highly vascular, contains osteoprogenitor (stem) cells that give rise to osteoblasts
therefore periosteum has osteoprogenitor capacity
endosteum is identical to ____ but found on the inner surfaces of bone
endosteum = periosteum, but on inner surface of bone
how are bones vascular
Haversian system allows passage of blood vessels, lymphatics
_____ allow blood vessels in bones to reach interior of bone
Volkman’s canal: in the Haversian system but perpendicular
matrix of compact bone
lamellae
lacuna vs lamellae vs canaliculi
Lacunae are small spaces in the lamellae. Lamellae act as the matrix of the compact bone. Lacunae act as an encase or hollow space for osteocytes or bone cells.
Bone canaliculi are microscopic canals between the lacunae of ossified bone.
osteoclasts are derived from ______ progenitors
osteoclasts are derived from macrophage-monocyte cell series (NOT mesenchymal as osteoblasts/cytes are)
appear as large, multinucleate cells, found at edges of periosteum
remodel bone via decalcification, form depressions called Howship’s lacuna
diarthrotic joints
aka synovial joints, provide freedom of motion
closed cavity lined by synovial membrane that produces synovial fluid
synovial membrane is only a few cells thick - NOT found on weight-bearing surfaces
synovial fluid contains large amounts of _____ that makes it slippery
hyaluronic acid
is articular cartilage (hyaline cartilage) on the ends of long bones covered by perichondrium?
no
____ are sacs filled with synovial fluid to provide friction-free movement and keep muscles and tendons from rubbing each other
bursa
_______ are non-synovial articulations that are more stable and provide less freedom from movement
synarthroses: cartilaginous (symphyses) or fibrous (sutures)
