Cells are the smallest living thing.

The cells connection to the outside world.
Absorption done through membrane.
Microvilli found in places where absorption takes place.

Where two cells come together.
Tight Junctions – keep things water tight.
Sm. Intestine
Desmosomes – Keeps cells together that are constantly under mechanical stress.
Skin. Uses protein filaments to increase stability
Gap Junctions – Allows for passing of materials from adjacent cells.

Group of cells with similar structure and function
Epithelium (covering), connective
(support), nervous (control), and muscle
(movement).

Nervous Tissue helps to control the body and pass signals from one organ to another.

Skeletal muscle – Connected to bones for voluntary movement. Long striations
Cardiac muscle – tissues of the heart.
Striated like skeletal muscle, but shorter in length.

Smooth muscle – no striations, found in hollow organs. Stomach, intestines, etc.

Protection, absorption, filtration and secretion
Characteristics
– Close together, make sheets
– Apical (free) surface
– Rests on basement membrane (bottom)
– Avascular – no blood vessels, depends on diffusion for oxygen and food
– Regenerate quickly.

Two types, simple (one layer) vs Stratified
(many layers)
Squamous – flat cells that fit together like floor tiles, making a flat sheet. Lung and esophogus tissue

Cuboidal – thicker then squamous
Columnar – elongated cells

Protects, supports, and binds tissues together.
Characteristics
– Vascularized – most have good blood supply
– Extracellular Matrix – nonliving substances outside of cells that help perform function
Cells make fibers that hold water, making connective tissue very durable.

Bone – cells surround by an extremely hard matrix that contains calcium and collagen.

Cartilage – more flexible then bone (matrix is softer). Mostly collagen, between bones

Dense connective tissue – collagen with fibroblasts. Tendons, ligaments, and lower skin layers

Loose Connective Tissue – softer with fewer fibers
Areolar Tissue – most abundant, keeps organs in place as well as stores water and salts
Adipose tissue – areolar tissue that has lipid containing cells in it.

Considered to be connective because it is a cell (erythrocyte) surrounded by a matrix
(blood plasma).
Fibers in matrix are only visible during clotting

Three levels
– Skin and mucus protect the body from the outside environment.
– In case of injury, inflammation occurs to help stop any further damage.
– Regeneration begins to fix broken or lost tissue

Capillaries open - allows clotting materials to exit blood stream and enter the wound.
Clotting agents seal the wound and stop outside invaders from entering the body.
Granulation tissue forms – pink tissue, mostly capillaries, that bring proteins to the wound site for regeneration. Bleeds freely
(picking a scab before it is fully healed)

Surface epithelium regenerates – granulation tissue gives way to brand new epithelium tissue and scar tissue.
Skin and mucous membranes heal very nicely, usually no scaring.
Muscle and nervous tissue heal poorly or not at all.

During childhood and adolescence the body is growing and almost all tissues are multiplying.
After adolescence, this changes.
Some tissues continue to reproduce normally, skin, intestines etc
Some stops, but can start again. Liver
Some stops completely. heart

Aging caused by
– Toxins
– Radiation
– Genes (telomeres)
Skin loses elasticity and sags
Bones become porous and weaker
Muscles Atrophy due to lack of use

Abnormal mass that grows when unneeded, aka tumor.
Benign – grow in a capsule that does not allow for cells to migrate, only dangerous if not removed before it gets so large that it pushes on important organs.
Malignant – not in a capsule, can Metastasis and travel around the body. Grows into good tissue causing functionality problems.