We'll Talk About the Other Stuff As We Need To

Tissues We'll talk about the other stuff as we need to. So, what are these things?  They are groups of similar cells that perform a particular function.  There are four major types ◦ Epithelial ◦ Connective ◦ Muscle ◦ Nervous  All tissues have an extracellular matrix ◦ This is a nonliving portion of the tissue

Epithelial Tissue  Function ◦ Protection, secretion, absorption, and excretion  Location ◦ Cover body surfaces, cover and line internal organs, compose glands  Distinguishing characteristics ◦ Lack blood vessels, readily divide, cells are tightly packed ◦ One side is always exposed to an open area ◦ Basement membrane the part of the extracellular matrix that anchors it to the connective tissue

Different types of epithelial tissues  Classified by shape and number of layers  There are nine different types ◦ Simple squamous - Stratified cuboidal ◦ Simple cuboidal - Stratified columnar ◦ Simple columnar - Transitional ◦ Psuedostratified columnar ◦ Stratified squamous - Glandular

Simple Squamous Epithelium  Simple – composed of only one layer of cells  Squamous – thin flattened cells  They look somewhat like floor tiles and their nuclei are usually broad and thin  Since stuff pass through them pretty easily, they are usually used at site of diffusion ◦ Alveoli in the lungs, capillaries, inside of blood vessels  Delicate, so it is easily damaged

Simple Cuboidal Epithelium  A single layer of cube shaped cells ◦ The nuclei are typically centrally located  Lines ovary, kidneys, and the ducts of other glands such as the salivary gland, thyroid, liver, and pancreas  In the kidneys it is used to secrete and absorb, in the glands it only secretes glandular products Simple Columnar Epithelium  A single layer of elongated cells (taller than they are wide) ◦ Nuclei are typically located near the basement membrane  They have other things added depending on their job ◦ Cilia to help create currents ◦ Small processes called microvilli to absorb ◦ Flask shaped glandular cells (goblet cells) to make mucus

Psuedostratified Columnar Epithilium  Look to be more that one layer, but are not. The appearance come from the nuclei being at different levels  Typically have cilia on the free surfaces  Line the respiratory system  Used for secretion, protection, and movement of mucus

Stratified Squamous Epithelium  Has many layers of the cells that are flattened in the upper layers  The cells divide in the deeper layers, and push the older layers outward  Make up the upper layer of the skin, the lining of the anal cavity, vagina, oral cavity, and the esophagus  Used for protection

Stratified Cuboidal Epithelium  Made of two to three cuboidal cells layers  Form the linings of lumens (openings) ◦ More layers = more protection  Line the large ducts of the mammary glands, sweat glands, salivary glands, and pancreas

Stratified Columnar Epithelium  Once again, made of many layers  The basal layers (base layers) are cuboidal, but the upper layers elongate  Found in the male urethra, vas deferns, and the pharynx  Used for protection and secretion

Transitional Epithelium  Specialized to change in response to increased tension  Used in area that expand and deflate  Forms the inner lining of the ureters and the urinary bladder  Not only changes shape, but prevents wastes from diffusing back into the body

Glandular Epithelium  Specialized to produce and secrete substances ◦ Into ducts – exocrine glands ◦ Into the body fluids – endocrine glands  Three main types ◦ Merocrine – releases secretions without loss of cytoplasm ◦ Apocrine – losses small portions of the cell body ◦ Holocrine – release entire cell filled with product

Connective Tissue  Binds structures together, provides, support and protection, serve as framework, fills space, stores fats, produces blood cells, fights against infections, and helps repair damaged tissues  Lots of extracellular matrix ◦ Can be fibers or a ground substance  Can usually divide, typically have a good blood supply

Major Cell Types  Fibroblasts – large star shaped cell ◦ Produce fibers  Macrophages – originate as white blood cells ◦ Carry out phagocytosis ◦ Move about and are scavengers and defenders  Mast cells – widely distributed, typically near blood vessels ◦ Release heprin and histamine

Connective Tissue Fibers  Collagenous fibers – thick threads of collagen proteins ◦ Grouped in long parallel bundles ◦ Not very elastic, but great tensile strength ▪ Really important in making ligaments and tendons which hold muscles and bones together ◦ appears white when a lot are together therefore sometimes called White Fibers

Some more fibers  Elastic Fibers – composed of elastin proteins ◦ Thin fibers branch forming complex networks ◦ Stretch easily,but not a lot of tensile strength ◦ Common in areas that are typically stretched ▪ Ex: vocal cords ◦ Sometimes called yellow fibers due to yellowish appearance when a number are together

Last fiber type  Reticular fibers – very thin collagenous fibers ◦ Highly branched ◦ Provide delicate supporting networks to many tissues ◦ Least common of the fibers

Loose Connective Tissue  AKA areolar tissue ◦ Delicate, thin membranes throughout the body ◦ Mainly made of fibroblasts and a gel-like extracellular matrix that has lots of fibers ◦ Binds skin to underlying organism fills space between muscles, lies under most layers of epithelium ▪ Special type- Adipose tissue (fat) forms within adipocytes. Lies beneath the skin and around other organs  Cushions joints and some organs and insulates as well as stores energy in fat molecules

Dense Connective Tissue  Consists of many densely packed, thick, collagenous fibers and a fine network of elastic fibers  Strong, so can withstand pulling  Used in tendons and ligaments  Also make up the sclera (the white of the eye)

Cartilage  Rigid connective tissue  Provides support, framework, and attachment points  Provides the structural models for many bones  Lots of gel-like matrix and collagen fibers  Chondrocytes (cartilage cells) live in small chambers and nutrients must diffuse to them from a perichondrium

Bone  Most rigid connective tissue ◦ Hardness due to storing mineral salts between the cells. This and the collagenous fibers make up the extracellular matrix ◦ Osteosytes are located in lacunae and rings of material is laid around them

Blood  Yep, it is a connective tissue  It travels about and transports many materials to body cells and the environment

Muscular Tissue  Are able to contract (shorten) in response to a specific stimuli. This causes something to move.  Three types ◦ Skeletal ◦ Smooth ◦ Cardiac

Skeletal Muscle Tissue  Found only in muscles that are attached to bones  Under voluntary control  Has long thread like cells with alternating light and dark cross-markings called striations and are multinucleated  Allows us to move the head, trunk, and limbs, as well as smile, talk, sing, chew, swallow and breath

Smooth Muscle Tissue  Called smooth because they have no striations  Are shorter than skeletal muscles and are spindle-shaped  Found in the walls of hollow internal organs  Typically involuntary

Cardiac Muscle Tissue  They are striated with a single nuclei and intercalated discs ( a special intercellular junction)  They are only found in the heart  They are involuntary also

Nervous Tissue  Found in the brain, spinal cord, and peripheral nerves ◦ Basic cell is called a neuron ◦ Neuroglial cells are the helper cells  They respond to changes in their environment  Used for sensory reception and conduction of nerve impulses