Flashcards in Lecture 5 - Bone and Cartilage Deck (57):
What is cartilage made of?
Dense regular connective tissue, Types II Collagen
mature form of chondroblast; secrete collagen type II, have large golgi (washed out). Inside a space within the matrix called lacunae.
What is it called when there are multiple cells in lacunae?
from cell division of pre-existing chondrocytes; occurs only in early stages of cartilage formation = "cell nest.” Results in articular cartilages and epiphyseal plates of long bones.
from chondrogenic cells in perichondrium. Results in formation of chondroblasts and or new chondrocytes. Results in new layer of cartilage matrix at periphery.
Where is hyaline found?
articular cartilage (joints), costal (ribs), fetal skeleton tissue, larynx, rings of trachea
What is hyaline composed of?
15% type II collagen for tensile & shear strength
10% proteoglycans for compressive strength
5% multiadhesive glycoproteins
and 5% chondrobalsts, chondrocytes, fibroblasts
What does hyaline have?
Perichondrium make up of dense irregular CT that makes membrane around hyaline and elastic cartilage. Perichondrium also has a cellular layer (chondrogenic layer) where chondroblasts reside.
What is the progression from fibroblast to isogenous groups?
Fibroblasts differentiate into chondroblasts
Chondroblasts mature into chondrocytes, which move towards the middle of the hyaline cartilage.
Form Isogenous groups/cell nest
Which is more flexible - hyaline or elastic cartilage?
What is Elastic cartilage made of?
Type II Collagen and Elastic Fibers
Which has more isogenous groups - hyaline or elastic cartilage?
Where is elastic cartilage found?
external ear, epiglottis, elastic arteries
Fibrocartilage - What is it made of?
Mix of dense irregular connective tissue and hyaline cartilage. Contains fibrocytes (making collagen I) and chondrocytes (making collagen II)
Where is fibrocartilage found?
invertebral discs, annulus fibrosus, meniscus, tendons, ligaments
Is cartilage vascular or avascular?
avascular - limited capacity for repair.
What is bone made of?
Collagen I - Calcified connective tissue forms structural component of bones.
What are the two types of bone in a bone?
Compact bones in the middle, spongy bone at the ends.
What are the functions of bones?
systems of levers, support, protection, bone marrow (in adults, mainly in flat bones), calcium & phosphate reservoir
end of bone (made of cancellous/spongy/trabecular bone). Can have bone marrow within spaces
shaft of bone (lamellar/compact bone) marrow cavity, bone marrow is mainly here. filled w/ hemopoetic tissue in kids, adipose tissue in adults (yellow marrow)
Small flanking region in bone between diaphysis and epiphysis.
In youth, area of cartilage responsible for growth in bone lenth, inadults, cartilage is gone, but line remains.
CT that covers outside of bone
Outer layer = fibrous, dense irregular CT + fibroblasts
Inner layer = cellular, osteogenic cells that become osteoblasts
Type I collagen fibers that extend into bone tissue and are continuous with collagen fibers of ECM. Attach periosteum firmly to bone.
Found on bone surface, differentiate into osteoblasts. Derived from mesenchymal stem cells.
What is the transcription factor that triggers differentiation of osteoprogenitor cells?
Core binding factor alpha-1 (CBFA-1)
Bone-producing cell found on the surface of bone. Synthesize collagen I and ground substances, trigger mineralization/calcification process.
What do osteoblasts depend on?
Vitamin K and growth factors
Osteoblast once it becomes surrounded by matrix. Maintains bone matrix/mineral content.
Osteoprogenitor cells that are inactive, just cover bone surface.
Derived from hemopoietic stem cells (CFU-GM) and are responsible for the destruction and breakdown of bone. Large multinucleated cells with microvillus/ruffed border.
What transcription factors are needed for osteoclast formation?
What type of cytoplasm do osteoclasts have?
Acidophilic cytoplasm that releases hydrolytic enzymes.
Attachment site to bone (tight seal), prevents leaking
Depression of dissolving bone
Functional unit of bone, made of harversian canal and lamellae. Found in compact bone (few in spongy)
Longitudinal channel that carries blood supply and nerves to the core of osteon.
connects adjacent Haversian canals
Layers of calcified fibrous tissue surrounding central canal (concentric circles); Arranged in perpendicular fashion to add length.
Open spaces where cell resides
little channels that allow diffusion from haversian canal to osteocytes; for nutrient and communication.
Connects osteocytes to other cells and BVs.
Exchange of nutrients is a dertermining factor in the diameter of an osteon.
Balance of creation/destruction of bone; occurs all the time. Bone is very dynamic.
Sequence of bone remodeling.
(1) Osteoclasts remove Osteons - Leaving cutting cone.
(2) Osteoblasts lay down new matrix - Closing cone.
(3) Osteoclasts will phagocytize dead cells.
Bone Fracture Steps
(1) Formation of granulation tissue (loose CT). Damaged cells will release transmitters that will attract lots of inflammatory cells granulocytes. Proliferation of capillaries and fibroblasts.
(2) Formation of soft callus. (loose tissue is replaced by dense connective tissue (hyaline cartilage), then by fibrocartilage.
(3) Formation of bony callus: Cartilage is replaced by bone.
(4) Remodeling - Reformed by osteoblasts and osteoclasts.
What are the two ways to do bone formation?
1. Endochondrial Ossification
2. Intramembranous Endochondral Ossification
Perichondrium, where osteoprogenitors reside. As it expands and dies, the cartilage is calcified and replaced by osteoblasts and osteocytes. Vessels enter the bone.
Primary ossification center = Diaphysis
Secondary ossification center = help distinguish which bone is more mature.
Bone length grows due to chondrocytic division in epiphyseal plate.
Where does endochondral ossification occur?
All bones but flat bones.
Mesenchymal cells differentiate directly to osteoblasts. First forms cancellous bone.
Bone CANNOT grow interstitially by itself; the length increases by interstitial growth of hyaline cartilage within epiphyseal plate, so when the plate closes, no more growth!
Bone CAN increase it diameter by appositional growth = adding new bone to preexisting bony surface. Thickness both on the periosteum and endosteum. Can happy in people of all ages.
Growth of small bones by appositional growth continues too much - Overproduction of growth hormone after puberty.
tumor occurs when epiphyseal plats are still open, lots of height growth - Overproduction of growth hormone during puberty.
Mutation knocks out sulfaction of carbohydrates; what structure does that affect the most?
Cartilege! It has a lot of sulfated fibers (this is the most dense regular CT! Very important!)