Imported and fixed: histology cartilage and bone

lecture 4

firm connective tissue is known as

cartilage and bone

Identify this tissue

Hyaline cartilage

Cartilage is connective tissue that consists of

chondrocytes
but majority is ECM (>95%)

Cartilage is (vascular/avascular)

avascular, receives nutrients by diffusion

Cartilage is firm and pliable, the 3 types are

hyaline, elastic, fibrocartilage

Location:Fetal, Articular, Respiratory, Costal Rib

Hyaline Cartilage

Location: Ear, Larynx, Epiglottis

Elastic Cartilage

Location of Cartilage: IVD, meniscus, TMJ

Fibrocartilage

Function of Cartilage:
Resist compression & cushioning

Hyaline cartilage

Function of Cartilage:
Resist compression & resist shearing forces

fibrocartilage

Function of Cartilage:
Flexible support

Elastic cartilage

Matrix of cartilage:

Collagen II
Aggrecan

Hyaline Cartilage

Matrix of cartilage:

Collagen II
Aggrecan
Elastic Fibers

Elastic Cartilage

Matrix of cartilage:

Collagen II
Collagen I
Versican, Aggrecan

Fibrocartilage

What cartilages have perichondrium?

Hyaline & Elastic cartilage only.
Fibrocartilage does NOT have perichondrium

All cells can grow by

intersital expansion

Cell divisions within the matrix, increases in length and girth

Intersitial growth

From perichondrium, form at surface, increases girth

appositional growth

Territorial Matrix (TM) vs. Interterritorial Matrix (IM)

TM: strong basophilic staining
IM: weak basophilic staining

Name what the arrow is pointing to

L to R: chondrocyte, ECM, lacuna
Top: nucleus

isogenous group

cluster of chondrocytes (cartilage cells) that originate from a single progenitor cell

commonly found within the lacunae (small spaces) of the cartilage matrix, particularly in hyaline cartilage

Identify the cartilage

Elastic cartilage is the most pliable cartilage --> it contains interlacing elastic fibers in addition to collagen fibers --> provides both form and flexibility

Fibrocartilage

A combination of dense connective tissue (has col I) and hyaline cartilage (has col II)

Proteglycans are (eosinophilic/basophilic) and have

basophilic, have negative charges

Collagens are (eosinophilic/basophilic) and have

eosinophilic, have positive charges

aggrecan

proteoglycan found in cartilage

ability to bind water is crucial for the cartilage's ability to resist compressive forces. water content allows cartilage to act as a shock absorber, providing cushioning to joints.

amount in cartilage determines and affects height; intervertebral disc (older=less)

What is a herniated disc in regard to bones?

Portion of the nucelus pulposus protudes into the inrervertebral foramen, pressing on one of the spinal nerves in the process

synovial joint

articular cartilage

no perichondrium

arthritis

caused by degradation of articular cartilage

Osteoarthritis

Caused by overuse and mechanic stress. Treatment via surgery, drugs such as condroitin sulfate, steroid, mild excercises

Connective tissue that is mineralized

Bone

Connective tissue that is not mineralized

Cartilage

ECM contains collagen II, collagen I, proteoglycan

Cartilage

ECM contains organic substances (collagen I fibers, ground substance proteoglycan) and inorganic structures (hydroxyapatite)

Bone

Function of cartilage

cushion, support

Function of bone

support & calcium/phosphate storage

Cartilage blood supply is

avascular

Bone blood supply is

vascular

Cartilage grows via what kind of growth

Intersitial and Appositional Growth

Bone grows via what kind of growth

appositional

Bone organ is made up of

• Bone tissue, hemopoietic tissue, fat tissue, blood vessels, nerves

• ECM made of:

  • organic:

    • collagen fibers, ground substance, proteoglycan

  • inorganic:

    • hydroxyapatite Ca10(PO4)6(OH)2

*need calcium for muscle from workout. get Ca from bone. used too much? not enough Ca for bone remodeling. osteopenia: bone mineral density is lower than normal but not low enough to be classified as osteoporosis

Identify the types of bone in this image

horizontal arrow: compact bone
top arrow: spongy bone

spongy bone VS compact bone:

structure, location, function

	compact bone	spongy bone
structure	organized into structural units called osteons aka Haversian system each osteon has central canal surrounded by concentric rings of calcified matrix called lamellae	composed of a network of trabeculae (thin, bony plates or beams) arranged along lines of stress to help the bone resist forces from multiple directions. spaces w/in spongy bone are filled with red bone marrow, where blood cells are produced
location	outer layer of bone	primarily at the ends (epiphyses) of long bones
purpose	protection, support, weight-bearing	lightweight, flexible, hematopoiesis, shock absorption

spongy bone

forms first, covered by white fat, has a lamellated matrix, gets nutrients by diffusion

No: haversian lamellae or interstitial lamellae

Transverse canals are only found in

compact bone

Haversian lamellae & Intersitial lamellae are/not present in spongy bone

NOT

what type of bone is this?

mature compact bone

what type of bone is this?

compact bone

what extends cytoplasmic processes into canaliculi and communicate with each other through GAP junctions?

osteocytes

Osteons are found in

compact bone only

Surface cells such as periosteal cells and endosteal cells that eventually give rise to osteoblasts

Osteoprogenitor

osteoclast vs osteoblast vs osteocyte

	osteocyte (3)	osteoblast (2)	osteoclast (4)	osteoprogenitor cells (1)
location	Embedded in bone matrix	Bone surface	Bone surface, near sites of bone resorption	Inner layer of periosteum, endosteum
function	Maintain bone matrix, sense mechanical stress surrounded by matrix	Build new bone, secrete bone matrix not yet surrounded by matrix secretes bne matrix	Break down bone, resorb bone tissue large multinuc cell derived from mononuclear hemopoietic cells phagocytotic	Differentiate into osteoblasts, bone repair
disease			osteopetrosis paget disease
disease synopsis			increased bone mass due to defect osteoclast, fragile bones, unerrupted teeth overactive osteoclast too much remodeling and not enough building; softer bones

what is the bone matrix comprised of:

col 1, osteocalcin, osteopontin, alkaline phosphatase, BSP

Secretes bone matrix but not yet surrounded by matrix

Osteoblasts

Responsible for matrix deposition, maintains bone matrix. Osteoblasts that are surrounded by matrix are now called

Osteocyte

Characteristics of Osteoclasts (4)

-Large multinucleated cells
-Derived from mononuclear hemopoietic cells
-Phagocytotic
-Responsible for bone resorption

Identify all the letters in this image A-E

A: osteocyte
B: osteoblasts
E: osteoblasts
D: osteoclasts
C: osteoclasts

Space created by osteoclast resorption

Howship's Lacuna

Collagen II is produced only by

chondrocytes

What is the difference between osteoblast and osteocyte?

osteoblast: not surrounded by matrix
osteocyte: immersed in matrix

Macrophages and osteoclasts are derived from

monocytes

Macrophages can be found in

connective tissue

Osteoclasts can be found in

bone

Osteoclasts-mediated bone resporption occurs in 3 ways

Decalcify through acidification
Degradation of bone matrix
Clean up

What happens in Decalcify through acidification ?

pumping out H+ protons, cytoplasmic infolding

What happens during degradation of bone matrix

digestion by enzymes released by lysosomes

What happens during the "clean up"?

endocytosis

Low bone mass, structure deterioration of bone tissue Bone fragility, and more susceptible to fracture

Osteoporosis

Increased bone mass, due to defect osteoclast function
Bone fragility, and more susceptible to fracture; Unerrupted teeth

Osteopetrosis

Increased bone remodeling, overactive osteoclast Softer bone, more susceptible to fracture

Paget disease