Tissue

Groups of cells with a common structure and function there are 4 types of tissue

Epithelial Tissue Covers the outside of the body (SKIN) and lines the organs and body cavities Classifications Simple – one layer of cells Stratified – multiple layers of cells Pseudostratified – appears multilayered because cells vary in length but is one layer of cells Cell Shape Squamous – flattened (looks like floor tiles) Cuboidal – box/cube like shape Columnar – columns like bricks standing up

Connective Tissue Functions to bind and support other tissues, sparse population of cells throughout an extracellular matrix Types Loose Connective – under most epithelial tissue, made up of elastic and collagen fibers as well as fibroblasts (cells that secrete fibers) Adipose Tissue – fat, cushions vital organs and place of energy storage, each cell contains a large fat droplet that swells when fat is stored and shrinks when the body uses fat as fuel. You never “lose” a fat cell unless it is removed via liposuction you can shrink the cell but not remove it

Fibrous connective tissue- makes up tendons (link muscle to bone) and ligaments (bone to bone) Hyaline and elastic cartilage- in nose, ear cells are in lacunae (small depression in the matrix) remember that your ears never stop growing Osseous (bone) – cells are in rings and have canals for blood vessels and nerves ( think about the sickle cell bone marrow transplant) Blood – red blood cells (erythrocytes), white blood cells (leukocytes) and platelets

Muscle Long cells called muscle fibers that are capable of contracting usually when stimulated by nerve signal they also have protein Types Skeletal muscle – voluntary movement striated muscle structure (bands due to filaments) multiple nuclei in the structure Smooth muscle – lacks striations found in digestive tract, bladder arteries and some other internal organs, including blood vessels controlled by nerves Cardiac muscle – forms the contracting wall of the heart. Striated and branched single nuclei. Includes intercalated discs that allow for the impulse that causes the heart to beat they relay signals between the cells

Nervous Tissue Senses stimuli and transmits signals in the form of nerve impulses from one part of the body to another Made up of individual cells called neurons which have : Cell body Axon – long portion conducts impulses away from cell body Dendrites – shorter, receives impulses

Organs In complex animals tissues organize and create organs which create organ systems the human body has 11 organ systems The largest organ in the human body is skin The layers of the skin from outside in:

Skin Epidermis: Upper layer, consists of epithelial tissue, outer layer is keratinized (keratin helps with wrinkles) Dermis : Thickest layer, consists of fibrous connective tissue and other structures: Hair: follicle, root Sebaceous gland: next to hair follicle secretes sebum (oil) can clog and cause infection and swelling Arrector pili muscle: causes hair to “stand up” Sweat glands Sense organs: pacinian corpuscles, missner’s corpuscles: sense touching pain Subcutaneous layer – adipose and loose connective tissue