2 Key Terms Histology: the study of tissues. Tissues: Simply groups of similar cells that work together performing the same taskGreatest form of teamwork in the body
3 Where are tissues found? With few exceptions, organs are composed of four basic tissue types:– Epithelial Tissue– Connective Tissue– Muscular Tissue– Nervous Tissue
4 Why Study Histology?Knowing the difference between normal and abnormal tissue is the first step in diagnosis and treatment of patients.
5 * made of all four tissue types Skin, our largest organ* made of all four tissue types
6 Epithelial Tissue Makes up 3% of your body weight They don’t move They don’t send messagesTheir cells are all touching one anotherOf all tissues, they are the most widely varied in structure and function
7 Locations of Epithelial Tissues Covers the body (epidermis)Found on the inside of hollow organs and the outside of all organsFound above a connective tissue layer (epi = above)Lines the cavities, tubes, ducts, and blood vessels inside the body
8 Epithelial AnatomyApical surface – upper surface that is free or exposed to the “exterior”Basal surface – attached surface (below)Microvilli – small fingerlike extensions that increase the surface area allowing for more work to be done
9 Functions of Epithelial Tissue Protects from physical & chemical injuryProtects against microbial infectionContains nerve endings which respond to stimuliFilters, secretes & reabsorbs materialsSecretes fluids to lubricate joints
10 Three Basic ShapesSquamous – like scales, or pancakes (“being squashed like a pancake”)Cuboidal – looks like cubesColumnar – longer and look like columns
11 Cell OrganizationSimple – single layer of cells; typically found where absorption and filtration occur or a single layer of epithelial is neededsimple squamoussimple cuboidalsimple columnarStratified – layers of cells; common in areas where protection is needed like the skinstratified squamousstratified cuboidalstratified columnar
12 Two Types of Stratified Columnar CiliatedUnciliatedciliaNo cilia
13 Squamous Epithelium Simple – one cell thick Forms solid layer of cells which line blood vessels, body cavities and covers organs in body cavitiesStratified – multiple layersForms epidermis
14 Cuboidal Epithelium Simple – one cell thick Roughly cube shaped Cuboid CellsSimple – one cell thickRoughly cube shapedDuctLine ducts in kidneys where re-absorption and secretion activities take place.Cuboid CellsDuct
15 Columnar Epithelium Simple – one cell thick Column shaped (long and narrow)Lines digestive tract where re-absorption & secretion occurs.
16 Confusing Epithelial Tissue Transitional Epithelium – stratified tissue that can’t make up its mind as to whether it is squamous or cuboidalShape of cells depends upon the amount of stretching (ex: bladder)
17 Confusing Epithelial Tissue Continued… “Pseudostratified Columnar Epithelium”Looks like it has more than one layer because of the position of the nucleusNuclei are positioned at differing levelsCells narrow in the area without the nucleus
19 Types of Epithelial Membranes Mucous or mucosa– lining of tubes; moistens and protects from enzymes (stomach, trachea, and vagina)Serous or serosa – outside of organs; lubricates (all thoracic, abdominal and pelvic organs)Cutaneous or skin – body surface; protectionSynovial – synovial joints; lines and protects synovial cavities (elbow, knee, hip, etc.)
20 Synovial MembranesSome joints are surrounded by a membrane (synovium) that produces a thick, synovial fluid. This fluid nourish the cartilage and keeps it slippery.Knee Joint
21 Mucosa MembranesMucus-secreting membrane that lines all body cavities or passages that come in contact with the outside of the body. Membranes are involved in absorption and secretion.Fungus
22 Serous MembranesSerous membranes line body cavities that do not open directly to the outside, and they cover the organs located in those cavities. Fluid lubricates the membrane and reduces friction and abrasion when organs move against each other.Canine Reproductive Organs
23 Cutaneous MembranesCutaneous membranes of the skin cover the surface of the body. They consist of stratified squamous epithelium and the underlying connective tissues. Cutaneous membranes are thick, relatively waterproof, and dry.Skin Cancer
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