EPHE 141: Cartilage -> Membranes & Fascia

Cartilage: main cells, protein fibers, vascularity, matrix viscosity, physical properties

• Main cells: chondrocytes that secrete collagen fibers and chondroitin sulfate (forms matrix)

• Main protein fibers: collagen (no reticulin)

• Avascular

• Firm gel matrix

• Strong and flexible

Perichondrium structure & function

• surrounds the cartilage

• Vascular

• 2 Layers: fibrous layer (dense CT), cellular layer (chondroblasts aka immature chondrocytes)

Why will cartilage heal better when it is found next to bone?

Cartilage itself is avascular, making it difficult to receive nutrients and diffuse molecules in and out. The perichondrium is the closest source of nutrients, because it is vascular (partly dense CT). However, bone is very well vascularized, so it is easier for cartilage to heal when there is bone nearby.

What are lacunae?

• small cavities in cartilage within firm gel ECM

• House chondrocytes (that produce & maintain matrix)

where are chondroblasts found?

Near the outer surface of cartilage, underneath the perichondrium

What is the difference between mesenchymal cells, chondrogenic cells, chondroblasts and chondrocytes?

They are at different stages in differentiation:

• mesenchymal cells are undifferentiated connective tissue

• chondrogenic cells are undifferentiated cartilage cells 

• chondroblasts are immature chondrocytes

• chondrocytes are the primary cell found in cartilage

Mesenchymal → chondrogenic → chondroblasts → chondrocytes

Hyaline cartilage: type of connective tissue, functions and locations

• A subtype of Supporting CT

Functions:

• cushioning and reinforcement of other tissues and organs

• serves as the structural support in the early embryonic skeleton before it is replaced by bone

Locations:

• early embryonic skeleton

• nasal septum

• between ribs and sternum

• covers articulating bone surfaces (like in synovial joints, where it is called articular cartilage and doesn’t have a perichondrium)

What kind of cartilage is the shiny part of the articulating surfaces of bones?

articular cartilage (hyaline cartilage)

Where does cartilage not have a perichondrium and what type of cartilage is it?

Articular cartilage (hyaline) found in synovial joints does not have a perichondrium

Elastic cartilage: type of connective tissue, functions & locations

• subtype of supporting CT

Functions:

• is resistant to/tolerates distortion

• has shape memory (resting position)

Locations:

• auricle of external ear

• epiglottis

Fibrous cartilage: type of connective tissue, functions & locations

• subtype of supportive connective tissue

Functions:

• resists compression

• prevents bone-to-bone contact

• limits excessive movement

Locations:

• intevertebral discs

• menisci

• pubic symphysis

List the four types of epithelial membranes in the body

• mucous membranes

• serous membranes

• cutaneous membranes

• synovial membranes

Mucous membranes: structure + tissue types, function, locations

• Structure: epithelial tissue (type depends on location) + areolar CT (called lamina propria, found under BM)

• Function: line interior passageways that communicate with the exterior, lines digestive tract with mucous (goblet/mucous cells)

• Locations: mouth (ET type = non-keratinized stratified squamous), digestive tract (ET type = simple columnar)

Serous membranes: structure/tissue types, function, locations

• Structure: mesothelium (simple squamous ET) + areolar CT

• ET secretes “serous fluid”

• Function: lines cavities that lack exterior openings

• 3 locations: pericardium (covers heart), pleura (covers lungs), peritoneum (covers enclosed organs in peritoneal)

Cutaneous membranes: common name, structure/tissue types, functions, location

• aka skin

• Structure: keratinized stratified squamous ET (epidermis) + areolar CT and dense irregular CT (papillary and reticular layers of the dermis)

• Functions: protects internal structures, first line of defense against environmental pathogens

Synovial membranes: structure/tissue types, function, locations

• Structure: synovial cells + CT (dense irregular, adipose, or areolar)

• Not true epithelium bc no BM, incomplete cell layer

• Function: joint lubrication via synovial fluid (produced by the synovial cells)

• Locations: synovial joints

Structure and function of fascia (in general)

• structure: strong bands of CT with lots of collagen, OR loose CT

• function: reducing friction, supporting nearby tissues