Tissues Four Main Categories of Tissues Epithelium Connective

Tissues

Four Main Categories of Tissues Epithelium Connective Muscle Nervous

Cheek Cells

Epithelial Tissue Features Divided into two categories 1. Covering/lining 2. Glandular �Arranged in continuous sheets �Single or multiple layers

Epithelial Tissue Features Tissues have: �Apical surface �Lateral surface �Basement membrane made up of mostly protein fibers

Epithelial Tissue Features �Is avascular �Has a nerve supply �Can regenerate �Cells packed tightly together

Epithelial tissue is named based on its description 1. 2. 3. 4. 5. simple = single layer stratified = multiple layers squamous = flat cuboidal = square columnar = column (rectangle)

Simple Squamous Function: Diffusion and filtration. Air sacs in lungs, walls of capillaries

Simple Cuboidal Function: Secretion and Absorption Found in: kidneys tubules, ducts and covering the ovaries

Simple Columnar Function: Secretion and Absorption Found in: Digestive tract and uterus *Contains goblet cells to secrete mucus *Can have microvilli

Stratified Squamous • Multi layer squamous cells • Function: protection • Found: In skin and mouth

Pseudostratified Columnar • Arranged in a single layer • nuclei are uneven which gives it a layered appearance • Can have goblet cells and cilia • Location: lining air passages and tubes of the reproductive system

Transitional Epithelium • Stretchable • Blocks diffusion (no leaking) • Found in the urinary bladder

Glandular Epithelium �Cells are specialized to produce and secrete substances �Glands – �Exocrine glands – secrete products into ducts �Endocrine glands – �Ex. pituitary, thyroid, adrenal

Connective Tissue � Most abundant tissue in your body Function: �Stores energy (fat) �Major transport system �Binds, protects and supports

Connective Tissue Features �Highly vascular �Except cartilage �Has nerves Consists of 1. Cells 2. Extra cellular matrix **cells vary based on the type of tissue

Types of Cells in Connective Tissue Fibroblasts �secrete protein to make fibers Macrophages �eat cell debris and bacteria Plasma Cells �secrete antibodies and attack foreign substances Mast Cells �produce histamine to prevent clots Adipocytes �store fat

1. Types of Fibers found in Connective Tissue Collagenous fibers �strong and flexible �E. x. bones, tendons and ligaments 2. Elastic fibers �very flexible �E. x. skin, blood vessel walls, lungs 3. Reticular Fibers �Provide support and strength, form stroma �E. x soft organs

Classification of Connective Tissue �Loose �Tissues are loosely arranged �Dense �Numerous thicker/denser fibers and fewer cells �Cartilage �Strong but flexible

Adipose Tissue (fat)

Lipid Nucleus of adipocyte Here is a close up of adipose tissue. You can see the large lipid containing adipocytes.

Adipocytes Here’s another view of adipose tissue.

Loose connective tissue is found in the dermis and subcutaneous layers of the skin as well as surrounding muscles. Sometimes it is called fascia.

Dense Connective Tissue • Tendons • Connect muscle to bone • Ligaments • Connect bone to bone

Cartilage • Cells are called chondrocytes • Provides support and attachments, also cushions bones

Hyaline Cartilage • Covers ends of joints, soft nose and respiratory passages (larynx and trachea)

Hyaline Cartilage Chondrocyte Lacunae � Has the characteristic chondrocyte in lacunae � “Ground glass” appearance to the matrix � Serves as a model for bone growth.

Hyaline cartilage

Another picture of hyaline cartilage. Nice “ground glass” matrix!

Elastic cartilage �Found in the external Ear and Larynx �Also has the characteristic chondrocyte in lacunae except with elastic fibers. Elastic fibers

Fibrocartilage Tough, shock absorbing

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Classification of Connective Tissue (Continued) �Bone �Protects, allow movement, produces necessary materials �Liquid Connective Tissue �Blood �Lymph

Muscle Tissue Function: movement and generate heat Types of Muscle Tissue: �Skeletal �Movement of bone �Smooth �Organ movement �Cardiac �Form wall of the heart

Nervous Tissue Made up of: �Neurons �Sense and respond to stimuli �Neuroglia �Protective and supportive functions

Tissue Repair �The replacement of dead or worn out cells �New cells are created through cell division from three locations �Stroma �Supporting connective tissues �parenchyma

Renewal Capacity Continuous renewal �Epithelial tissue �Some types of connective tissue �Bone vs Cartilage Poor capacity �Muscle tissue �Nervous tissue

The Stem Cell Debate 1. How far should researchers take stem cell technologies? Just because we can do something, should we? Why or why not? 2. Do embryonic stem cells represent a human life? This is an ongoing debate that brings up the question of when life begins. Should the embryo or fetus have any rights in the matter? Who has the authority to decide?

Parenchymal Cells vs Fibroblasts �Regeneration is possible if parenchymal cells do the repair �Why? �If fibroblasts do the repair the injured tissue is replaced with connective tissue �Scars form �Results in impairment of original tissue function

Aging and Tissues �Younger cells have a better blood supply and are in a better nutritional state �Glucose and aging �Elastin and aging