TISSUE - TISSUE MEMBRANE - EFFECTS OF AGING ON TISSUES

Tissue Membrane

a thin sheet of tissue that covers a

structure or lines a cavity

● mucous

● serous

● synovial

3 Major categories of Internal

Membranes:

Mucous Membrane

● epithelial layer overlying

connective tissue (lamina propria);

often contains goblet cells that

secrete mucus

● protects underlying tissues, traps

debris and microbes, lubricates

surfaces

● lines body cavities that open to the

outside of the body

Serous Membrane

● structure: simple squamous

epithelium (mesothelium) over

connective tissue; produces serous

fluid (lubricates serous

membranes)

● reduces friction between organs

and body cavity walls

● lines closed body cavities and

covers organs, ex; pleura,

pericardium, peritoneum

Synovial Membranes

● connective tissue only (no

epithelium); contains cells that

secrete synovial fluid (rich in

hyaluronic acid)

● lubricates joints, nourishes

cartilage, reduces friction

● lines synovial (freely movable)

joints, e.g., knee, elbow, shoulder

Inflammation

- response that occurs when tissues

are damaged

Inflammatory Response

- mobilizes the body's defenses,

isolates and destroys

microorganisms and other injurious

agents, and removes foreign

materials and damaged cells so the

tissue repair can proceed

Chemical Mediators

● chemical substances that are

released/ activated in tissues and

adjacent blood vessels

● ex; histamine, kinins,

prostaglandins, leukotrienes and

etc.

Edema

- increases the pressure in the tissue,

which can also stimulate neurons

and cause pain

Tissue Repair

- the substitution of viable cells for

dead cells by regeneration/

replacement

Regeneration

the new cells are the same type as

those that were destroyed, and

normal function is usually restored

Replacement

a new type of tissue develops

which eventually produces a scar

and causes the loss of some tissue

function

Labile Cells

● cells that continue to divide

throughout life

● includes adult stem cells, other

cells of the skin, mucous

membranes, hemopoetic &

lymphatic tissues

● damage to these cells can be

repaired by regeneration

Stable Cells

● cells that do not normally divide

but can regenerat if needed after

injury

● provided limited repair and

regeneration

Permanent Cells

- have very limited ability to

replicate, if killed, they are usually

replaced by a different type of cell

Primary Union

● healing process where the edges of

a wound are close together

● Process: Minimal tissue loss →

wound edges join → small

clot/scab forms → little granulation

tissue needed → scar is small

Secondary Union

● healing process where the edges of

a wound are far apart or tissue loss

is extensive

● Process: Large clot forms → more

inflammation → lots of granulation

tissue → wound closes slowly →

scar is larger

Fibrin

a thread like protein contained by a

clot that binds the edges of the

wounds together

Scab

formed when the surface of the clot

dries & seals the wound and helps

provide infection

Pus

killed neutrophils that accumulate

as a mixture of dead cells and fluid

Granulation Tissue

a delicate granular-appearing

connective tissue that consists of

fibroblasts, collagen, capillaries,

and replaces the clot

Scar

a large amount of granulation

tissue which consists of dense

irregular collagenous connective

tissue

Wound Contracture

● definition: The process where a

healing wound shrinks in size due

to contraction of fibroblasts and

myofibroblasts

● function: Helps close wounds

quickly by pulling the edges

together

● problem: Can lead to deformity or

restricted movement if excessive

(common in burns)