Cells and Tissues Chapter 3

Cells Cells are the smallest living thing.

Membrane

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

Membrane Junctions 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.

Membrane Junctions

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

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

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

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

Epithelial Tissue 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.

Epithelial tissue 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

Epithelial Tissue Cuboidal – thicker then squamous Columnar – elongated cells

Connective Tissues 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.

Types of Connective Tissue Bone – cells surround by an extremely hard matrix that contains calcium and collagen.

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

Types of Connective Tissue Dense connective tissue – collagen with fibroblasts. Tendons, ligaments, and lower skin layers

Types of Connective Tissue 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.

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

Tissue Repair 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

Regeneration 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)

Regeneration 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.

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

Neoplasm 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.