Lab Exercise 6: Classification of Tissues

a group of similar cells arise from the same region of the embryo and have the same structural and physiologic function.
Two or more different tissues and have a specific function and recognizable shape.
study the structures of tissues by using a microscope.
covers exposed surfaces, lines passageways, forms glands
Connective Tissue
fills internal spaces, provides structural support for other tissues, transports material within the body, stores energy reserves.
specialized for contraction
Nervous Tissue
transmits information from one part of the body to another
Epithelial Tissue
o Physical protection of underlying tissues
o Control permeability
o Produce specialized secretions
Endocrine Glands
lose their surface connection (ducts) as they develop; thus they are referred to as ductless glands. Their secretions (all hormones) are released into extracellular fluid, from which they enter the blood or lymphatic vessels that weave through the glands.
Exocrine Glands
retain ducts, and their secretions empty through these ducts to an epithelial surface. This includes sweat and oil glands. Liver and Pancreas are both external and internal.
Epithelial Tissue
General Characteristics:

o Layers/sheets of closely packed cells, very little intercellular material
o Cells have polarity.
One surface (Apical) faces a lumen, space, or exterior of the body.
The other surface (Basal) is attached to a basement membrane or basal lamina.
o Avascular. Epithelial tissues lack blood vessels. Cells obtain nutrients and O2 by diffusion or absorption.
o Capable of regeneration. Epithelial cells divide continuously to replace damaged or lost cells.
The surface that faces a lumen, space, or exterior of the body.
The other surface is attached to a basement membrane or basal lamina.
Epithelial tissues lack blood vessels. Cells obtain nutrients and O2 by diffusion or absorption.
Epithelial cells divide continuously to replace damaged or lost cells.
Simple Epithelial
consisting of one layer of cells attached to the basement membrane.
Stratified Epithelial
consisting of two or more layers of cells.
Pseudostratified Epithelial
simple columnar epithelium (one layer of cells), but because its cells vary in height and the nuclei lie at different levels above the basement membrane, it gives the false appearance of being stratified. Often it is ciliated.
Cells fit together tightly because of hexagonal shape, nuclei are slightly squished (not perfectly round)
Cells are shaped like cubes, nuclei are round
Cells are long and rectangular, nuclei are stretched into ovals
The basal cells are generally cuboidal or columnar, while the surface cells are dome shaped or squamous. However, its appearance can very greatly depending on how stretched the organ is.
Simple Squamous Epithelium
Location: Kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosa)

Function: Allows passage of materials by diffusion and filtration in sites where protections is not important, secretes lubricating substances in serosae
Simple Cuboidal Epithelium
Location: Kidney tubules, ducts, and secretory portions of small glands, ovary surface

Function: Secretion and absorption
Simple Columnar Ciliated Epithelium
Location: lines small bronchi, uterine tubes, and some regions of the uterus.

Function: propel mucus by ciliary action
Simple Columnar Non-Ciliated Epithelium
Location: line most of digestive tract, gallbladder, excretory ducts of some glands.
Function: Absorption, secretion of mucous, enzymes, and other substances
Pseudostratified Ciliated Columnar Epithelium
Location: trachea, most of the upper respiratory tract.

Function: Secretion of mucus, propulsion of mucus by ciliary action
Stratified Squamous Keratinized Epithelium
Location: epidermis of the skin

Function: Protect underlying tissues in areas subjected to abrasion
Stratified Squamous Non-Keratinized Epithelium
Location: moist linings of the esophagus, mouth, and vagina

Function:Protect underlying tissues in areas subjected to abrasion
Transitional Epithelium
Location: Lines the ureters, urinary bladder, and part of the urethra

Function: stretches readily and permits distension of urinary organ by contained urine.
Connective Tissue
o Form the structural framework of the body
o Transport fluids and dissolved materials
o Protection
o Support, surround, and connect other tissues
o Storing energy reserves
o Defense against pathogenic microbes
Connective Tissue
General Characteristics:
o Contain specialized cells

o Have an extracellular matrix composed of ground substance and fibers.

o Many are highly vascular and innervated (there are several exceptions to this)
cells responsible for building the ground substance and the matrix (collagen, reticular, and elastic fibers, etc.) found in all connective tissues.
Irregularly shaped with short branching projections.
Develop from monocytes.
Function: Phagocytosis (engulf bacteria, dead cells, and foreign material), activate immune system. There two types of macrophages:
• Fixed macrophages: spend long periods in tissue.
• Wondering macrophages: migrate rapidly through tissues.
Fat cells contain lipid droplet.
The nucleus, organelles, and cytoplasm are squeezed to the peripheral.
The number of fat cells varies from one connective tissue to another.
Found below the skin and around the organs such as heart and kidneys.
Mesenchymal cells
These are stem cells that are present in many connective tissues. They divide to produce daughter cells that differentiate into other connective tissue cells.
Synthesize melanin.
Abundant in skin and eyes.
Mast cells
Small, mobile cells.
Abundant alongside blood vessels.
Secret histamine that dilate blood vessels and heparin that inhibit blood clotting.
Interstitial fluid enters these vessels.
Connective tissue consists of clear fluid similar to blood plasma with much less protein.
Collagen fibers
most common type of fiber. strong and stretch resistant. extremely abundant in tendons; stops bones from gliding.
Elastic fibers
rubber-like flexible protein.
Reticular fibers
forms interwoven framework. extremely thin. supports organs and resistant damage.
Connective tissue proper
contains many cell types and extracellular fibers in a soft syrupy ground substance. Separated into loose and dense categories.
Fluid connective tissues
populations of cells suspended in a liquid matrix which also contains proteins.
Supporting connective tissues
cell types are less diverse than other groups, matrix is more densely packed with fibers, matrix may be like a gel or solid (calcified)
Loose Connective Tissue: Areolar
Functions: Wraps and cushions organs. Macrophages phagocytize bacteria. Plays important role in inflammation. Holds and conveys tissue fluid.

Locations: Widely distributed under epithelia of body. Packages organs and surrounds capillaries.
Loose Connective Tissue: Reticular
Functions: Fibers form soft internal skeleton (stroma) that supports other cell types including WBC's, mast cells, and macrophages

Locations: Lymphoid organs (lymph nodes, bone marrow, and spleen)
Loose Connective Tissue: Adipose
Functions: Provides reserve fuel, insulates against heat loss, supports/protects organs.

Locations: Found under skin, around kidneys and eyeballs, abdomen in breasts
Dense Connective Tissue: Dense irregular
Functions: Able to withstand tension exerted in many directions; provides structural strength
Locations: Fibrous capsules of organs and joints, dermis of skin, submucosa of digestive tract
Dense Connective Tissue: Dense regular
Functions: Attaches muscles to bones or to muscle, withstands great tensile stress when pulling force is applied in one direction

Locations: Tendons, most ligaments, aponeuroses
Dense Connective Tissue: Elastic
Functions: allows recoil of tissue following stretching; maintains pulsate flow of blood through arteries; aids passive recoil of lungs following inspiration

Locations: walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tubes
Osseous: Bone
Function: Support and protect (by enclosing); provides levers for the muscles to act on; stores calcium; marrow inside bones is the site for blood cell formation (hematopoiesis)

Location: Bones
Hyaline cartilage
Function: support and reinforces; has resilient cushioning properties; resists compressive stress

Location: forms most of the embryonic skeleton, covers the ends of long bones in joint cavities, forms costal cartilage of the ribs, cartilage of the nose, trachea, and larynx
Elastic cartilage
Function: Maintains the shape of a structure while allowing great flexibility

Location: Supports the external ear (pinna); epiglottis
Function: Tensile Strength with the ability to absorb compressive shock

Location: Intervertebral discs; pubic symphysis; discs of knee joint
Function: Transport of respiratory gases, nutrients, wastes

Location: within blood vessels
Nervous Tissue
Function: Transmit electrical signals from secondary receptors and to effectors (muscles and glands) which control their activity

Location: Brain, spinal cord, and nerves
Skeletal muscle
Function: Voluntary mvmt, locomotion, manipulation of environment, facial expression, voluntary
Location: areas where this tissue attaches to bones or occasionally skin
Cardiac muscle
Function: As it contracts, it propels blood into circuation. Involuntary.

Location:Walls of the heart.
Smooth muscle
Function: Propels substances or objects along internal passageways, involuntary

Location: Mostly in walls of hollow organs