Lecture 16 - Connective Tissues Flashcards
Connective tissues
Most abundant and widely distributed of the primary tissues.
Functions: binding and support, protecting, insulating, storing reserve fuel, and transporting substances (blood).
Four main classes: connective tissue proper, cartilage, bone and blood.
Characteristics of connective tissues
All connective tissue arises from an embryonic tissue called mesenchyme (Greek, “middle-filling”).
Most connective tissue is highly vascularized, but tendons and cartilage are not.
composed mainly of nonliving extracellular matrix (a protein-sugar mesh) that separates the cells of the tissue. This matrix supports cells so that they can bear weight and withstand tension.
Three main elements of connective tissue
Ground substance
Cells
Fibres
What makes up extracellular matrix?
Ground substance and fibres together
What are blast cells?
Immature “blast” cells actively secrete ground substance and extracellular fibres.
Fibroblasts are found in connective tissue proper
chondroblasts are found in cartilage
osteoblasts are found in bone
What are mature cyte cells?
Mature “cyte” cells (example: fibrocytes) are less active and help maintain the health of the matrix
Fat cells
Store nutrients
White blood cells
as neutrophils, eosinophils and lymphocytes (including plasma cells), respond to tissue injury.
Mast cells
initiate a local inflammatory response against foreign microorganisms they detect.
Call WBCs if there is a problem
Macrophages
phagocytic white blood cells that “eat” dead cells and microorganisms as part of their function in the immune system.
Eat things that don’t look right
What is a Ground substance?
an unstructured gel-like material that fills the space between the cells.
Collagen fibres
extremely strong and provide high tensile strength to the connective tissue.
Ex. Scar tissue
Elastic fibres
contain elastin, which allows them to be stretched and to recoil.
Reticular fibres
fine, collagenous (but different from collagen) fibres that form branching networks where connective tissue contacts other types of tissues.
Areolar connective tissue
serves to support and bind body parts, contain body fluids, defend against infection, and store nutrients.
It is the universal packing material between other tissues.
Ex. Under skin
Adipose (fat) tissue
a richly vascularized tissue that functions in nutrient storage, protection, and insulation.
Almost entirely cells
Brown fat uses lipids to produce heat. (babies have more, harder to maintain body heat without)
Reticular connective tissue
forms the internal mesh-like stroma that supports the lymph nodes, the spleen and bone marrow.
Dense regular connective tissue
contains closely packed bundles of collagen fibres running in the same direction and makes up tendons and ligaments.
No blood vessels
Strong when pulled in direction they are meant to be pulled in
Dense irregular connective tissue
contains thick bundles of collagen fibres arranged in an irregular fashion and is found in the dermis
Collagen going in more than one direction
Elastic connective tissue
found in select locations and is more stretchy than dense regular connective tissue.
Expand and rebound
Cartilage
Cartilage grows from chondrocytes, lacks nerve fibres, and is avascular.
Matrix secreted from chondroblasts (during growth) and chondrocytes (as adults).
Chondrocytes found in cavities called lacunae (empty spot, lake or pool).
Because it is avascular, cartilage receives nutrients from the membrane surrounding it, called the perichondrium.
Hyaline cartilage
the most abundant skeletal cartilage and includes the articular, costal, respiratory, and nasal cartilages.
Provides firm support with some pliability. It is found at tips of long bones, nose, trachea, larynx, and cartilage of the ribs
Elastic cartilages
more flexible than hyaline and are located only in the external ear and the epiglottis of the larynx.
found where strength and exceptional stretch are needed, such as the external ear and epiglottis
Fibrocartilage
located in areas that must withstand a great deal of pressure or stretch, such as the cartilages of the knee and the intervertebral discs.
Cartilage growth
Appositional growth occurs when cartilage gets bigger from the perichondrium. New matrix is laid down on the surface of the cartilage.
Interstitial growth occurs when the cartilage matrix expands from the middle due to division of lacunae-bound chondrocytes and secretion of matrix within the cartilage.
Calcification of cartilage
occurs during normal bone growth in youth, but can also occur in old age.
Hardened cartilage is not the same as bone.
Bone (osseous) tissue
has an exceptional ability to support and protect body structures due to its hardness, which is determined by the additional collagen fibres and calcium salts found in the extracellular matrix
Blood (connective tissue)
classified as a connective tissue because it develops from mesenchyme and consists of blood cells and plasma protein fibres surrounded by blood plasma.
The fibres are soluble proteins that precipitate during blood clotting
