Histology The Study of Tissues Tissues A tissue

Histology: The Study of Tissues

Tissues ¥A tissue is a group of similar cells specialized for a particular function ¥ Classified according to their structure & function ¥ Four Primary Tissue Types Epithelial – covering ¥ Connective – support ¥ Muscular – movement ¥ Nervous - control ¥

Epithelial Tissue - Epithelium ¥ Lining, covering, & glandular tissue of the body. ¥ Forms glands, outer layer of skin, & lines body cavities ¥ Contains many cells, close together with no blood vessels. Can easily regenerate ¥ Rely on diffusion from capillaries for food & oxygen ¥ Functions ¥ Protection, absorption, filtration, & secretion

Classification of Epithelium ¥ Classified according to cell shape & arrangement ¥ 3 cell shapes Squamous: flattened ¥ Cuboidal: cube-shaped ¥ Columnar: column shaped ¥ ¥ 2 Arrangements Simple epithelium: one layer of cells ¥ Stratified epithelium: more than one cell layer ¥

Classification of Epithelium ¥ Simple Squamous ¥ ¥ Simple Cuboidal ¥ ¥ Single layer of flattened cells Diffusion & filtration Lines the lungs, kidneys, heart & blood vessels Single layer of cube-shaped cells Secretion & absorption Covers ovaries, kidneys, & eyes Simple Columnar ¥ ¥ ¥ Single layer of elongated cells Absorption & secretion of mucus Lines the entire digestive tract

Simple Squamous

Simple Cuboidal

Simple Columnar

Classification of Epithelium ¥ Stratified Squamous Protective tissue – outer portion of the skin ¥ Lines the mouth & esophagus ¥ ¥ Stratified ¥ Cuboidal Adult sweat glands, portions of the pharynx, & epiglottis ¥ Stratified Columnar Protects & secretes ¥ Male urethra & large excretory ducts ¥

Stratified Squamous

Stratified Cuboidal

Stratified Columnar

Connective Tissue Most abundant tissue in the body ¥ Fewer cells with a rich blood supply ¥ ¥ ¥ except for tendons, ligaments, & cartilage Produces an extracellular matrix (ECM) Non-living substance found outside of cells ¥ Allows connective tissue to bear weight, stretch, & tolerate abrasion ¥ Can be soft (fat) or hard (bone) ¥ ¥ Functions Protects, supports, and binds together organs ¥

Types of Connective Tissue ¥ Bone ¥ ¥ ¥ Cartilage ¥ ¥ Bone cells surrounded by very hard ECM Protects & supports body organs Less hard & more flexible then bone Embryonic skeleton, ends of bones, nose, attaches ribs to breast bone, external ear, between vertebrae, etc. Provides for movement & support Dense Connective Tissue ¥ ¥ Forms tendons & ligaments Close packing of fibers

Types of Connective Tissue ¥ Loose Connective Tissue Softer with more cells & fewer fibers ¥ Various types ¥ Adipose tissue – fat storage + body insulation ¥ Areolar tissue – cushions & protects body organs ¥ Reticular connective tissue – interlacing reticular fibers ¥ ¥ ¥ Blood Found in the liver, spleen, & lymph nodes – Vascular Tissue Blood cells & blood plasma ¥ Transport vehicle for the cardiovascular system ¥

Bone

Muscle Tissue Highly specialized to contract (shorten) to produce movement ¥ Three types ¥ ¥ Skeletal muscle Striated – banded ¥ Voluntary movement ¥ ¥ Smooth muscle No striations ¥ Involuntary movements ¥ Breathing, digestion, birth, reflexes, etc. ¥ ¥ Cardiac muscle Found only in the heart – striated ¥ Involuntary control – pumps the heart ¥

Nervous Tissue ¥ Neurons – nerve cells ¥ ¥ Unique structure: 3 parts ¥ ¥ Receive & conduct impulses from one part of the body to another Dendrites – receive message Cell body – interprets message Axon – conducts the message There are 100 billion neurons in the brain alone

Nervous Tissue ¥ Supporting ¥ ¥ cells (neuroglia) insulate, protect, & supports the neurons

Tissue Inflammation & Repair An attempt to restore homeostasis ¥ Damage causes inflammatory response ¥ ¥ ¥ Chemicals in the body initiate inflammatory responses & isolate infected area ¥ ¥ Redness, pain, heat, swelling Pus is often produced – can form an abscess Damaged tissue is then replaced by healthy cells ¥ ¥ ¥ Tissue repair is completed after harmful substances are removed/neutralized Vit. A, B, C, D, E, &K help tissue repair Needs adequate blood circulation – process slows with aging