Administration
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
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