Lab 2: Connective Tissue, Cartilage, and Bone

What is the most abundant type of tissue?

connective tissue

extracellular matrix

made of fibers and amorphous ground substance

• cartilage → gel matrix

• bone → hard matrix

• blood → liquid matrix

ECM cartilage

gel matrix

Bone ECM

hard matrix

blood ECM

liquid matrix

ground substance

well hydrated gel that fills the space between cells, fiber, and vessels

ground substance components

glycoproteins

glycosaminoglycans

roles of ground substance

reservoir for interstitial fluid

provides a medium for by-products to diffuse to and from cells

• oxygen

• nutrients

What fibers are most abundant?

collagenous

fibers

collagenous

reticular

elastic

special stains differentiate these

collagenous fibers

most abundant

• collagen → strong and flexible, resist stretch

• pink, shiny, fine or coarse, somewhat wavy

reticular fibers

• collagen → delicate, branching

elastic fibers

• elastin - stretchy

• fine to course

fibroblasts

most numerous cell in connective tissue

form fibers and ground substance

macrophages (histiocytes)

derive from monocytes of the blood

phagocytic → might have debris inside cytoplasm

cells of connective tissue

fibroblasts

macrophages

other

• neutrophils

• eosinophils

• lymphocytes

• plasma cells

• adipocytes

• mast cells

• globular leukocytes

connective tissue proper types

loose (areolar)

dense

reticular

elastic

adipose

other types of connective tissue

cartilage

bone

blood

bone marrow

loose (areolar) connective tissue

ground substance predominates

scattered cells of various types

blood vessels

loose network of fine collagenous, reticular, and elastic fibers

all over the body

• around vessel sand nerves

• serous membranes- mesentery, lamina propria of mucous membrane, subcutaneous tissues, superficial dermis, etc.

dense connective tissue

AKA fibrous tissue

thick collagenous fibers predominate

contains fewer cells than loose CT

• mostly fibroblasts

dense irregular and regular tissue

dense irregular connective tissue

3D meshwork of collagenous fibers arranged in all directions

• deep layers of dermis, submucosa of digestive tract in some species, capsules of organs

dense regular connective tissue

closely packed, parallel bundles of collagenous fibers

• tendons, ligaments, aponeuroses

Which CT type is located in deep layers of dermis, submucosa of digestive tract in some species, and in capsules of organs?

dense irregular CT

Which CT type is found in tendons, ligaments, and aponeuroses?

dense regular tissue

reticular tissue

reticular fibers predominate

support network → “skeleton” for the tissue

spleen, lymph node, liver, kidney, bone marrow

Which CT is found in the spleen, lymph node, liver, kidney, and bone marrow?

reticular tissue

Which CT type is found in vocal ligaments and ligamentum nuchae?

elastic CT

elastic tissue

elastic fibers predominate

• regular

• irregular

vocal ligamentum ligamentum nuchae

adipose tissue

AKA fat

adipocytes predominate

mesentery, subcutis, sheaths of vessels and nerves

3 types of cartilage

hyaline

elastic

fibrocartilage

cartilage components

chondrocytes

extracellular matrix

chondrocytes

cartilage cells

shrink during slide prep

lacunae → space where cell resides

Cartilage is surrounded by…

dense irregular connective tissue

hyaline cartilage

most common type of cartilage

matrix is made up of collagenous fibers

chondrocytes in lacunae

found in

• developing skeleton

• epiphyseal discs

• articular cartilages

• trachea and bronchi

Which cartilage is found in developing skeleton, epiphyseal discs, articular cartilages, trachea, and bronchi?

hyaline cartilage

elastic cartilage

similar to hyaline cartilage

matrix is made of elastic fibers

found

• epiglottis

• larynx

• pinna

Which cartilage is found in the pinna, larynx, and pinna?

elastic cartilage

fibrocartilage

AKA fibrous cartilage

a combination of hyaline cartilage and dense connective tissue

found

• intervertebral discs

• pubic symphysis

• cardiac skeleton

• in some tendons close to their attachment to bone

Which cartilage is found in the intervertebral discs, pubis symphysis, cardiac skeleton, and in some tendons close to their attachment site?

fibrocartilage

bone is an organ made of…

bone tissue

bone marrow

dense connective tissue

vessels

periosteum

endosteum

periosteum

dense connective tissue on the surface of the bone

• not where articular cartilage is present

endosteum

epithelial cells that line the marrow (medullary) cavity of the bone

bone matrix

living, dynamic connective tissue

relatively light weight

high tensile strength

• matrix of amorphous ground substance, collagenous fibers, hydroxyapatites crystals (calcium and phosphorus salts)

cells of bone tissue

osteoblasts

osteoprogenitor stem cells

osteocyte

osteoclasts

osteoblasts

basophilic (blue)

deposit ground substance and fibers of the bone matrix

osteoid → mineralizes → bone matrix

produced in layers (lamellae)

osteoprogenitor stem cells

give rise to osteoblasts

osteocyte

maintain the integrity of the matrix

a matured osteoblast

surrounded by bone matrix

flat with numerous processes

space called lacuna

processes are within canaliculi (tiny channels in the matrix)

• associated with blood vessels → diffusion of nutrients and wastes

osteoclasts

large, multinucleated cells that border bone surfaces

resorb bone matrix as necessary during development, remodeling, and repair

types of bone

compact

spongy

spongy bone

AKA cancellous bone

more space than bone matrix (looks like a sponge)

interconnected meshwork of small pieces called spicules or trabeculae

compact bone

AKA dense or lamellar bone

more bone matrix than space

densely packed layers of bone matrix with osteocytes sandwiched between the layers

• circumferential lamellae - diaphysis

• concentric lamellae - rings of layers called Haversian systems

In what bone is spongy bine situated between two layers of compact bone?

flat bone of skull

In what bone does compact bone forms the outer shells of the diaphysis and epiphysis, while spongy bone is in the interior of the epiphysis and the endosteal surface portions of the diaphysis?

long bones

intramembranous ossification

osteoblasts directly deposit bone matrix in or beneath a membrane

endochondral ossification

bone tissue replaces hyaline cartilage

epiphyseal plates

growth plates

loose connective tissue (canine jejunum)

dense irregular connective tissue (equine haired skin)

dense regular connective tissue (equine tendon)

elastic connective tissue (feline pinna)

elastic connective tissue will always be found…

alongside elastic cartilage

reticular connective tissue (ovine liver)

reticular CT (feline spleen)

reticular CT (ovine lymph node)

adipose CT (feline, fat)

hyaline cartilage (feline lung)

elastic cartilage (feline external ear canal)

compact bone (pink, solid)

spongy bone (purple)

feline humerus bone

spongy bone (pink)

articular cartilage (purple)

Equine P1 cartilage and bone