Tissues Body Tissues Groups of Cells are specialized

Tissues

Body Tissues · Groups of Cells are specialized for particular functions · Four primary types · Epithelium · Connective tissue · Nervous tissue · Muscle

Nervous tissue: Internal communication • Brain, spinal cord, and nerves Muscle tissue: Contracts to cause movement • Muscles attached to bones (skeletal) • Muscles of heart (cardiac) • Muscles of walls of hollow organs (smooth) Epithelial tissue: Forms boundaries between different environments, protects, secretes, absorbs, filters • Skin surface (epidermis) • Lining of GI tract organs and other hollow organs Connective tissue: Supports, protects, binds other tissues together • Bones • Tendons • Fat and other soft padding tissue Figure 4. 1

Epithelial Tissues · Body coverings · Body linings · Glandular tissue · Functions · Protection · Absorption · Filtration · Secretion Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 3. 42

Epithelium Characteristics · Cells fit closely together · has one free surface (apical) · The lower surface is bound by a basement membrane (glycoprotein-Collagen) · Avascular (have no blood supply) · Regenerate easily if well nourished

Classification of Epithelium · Number of cell layers

Classification of Epithelium · Shape of cells

Simple Epithelium · Simple squamous · Usually forms membranes · Lines body cavities. Lines lungs and capillaries

Simple Epithelium · Simple cuboidal · Common in glands and their ducts · Forms walls of kidney tubules · Covers the ovaries

(c) Simple columnar epithelium Description: Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucussecreting unicellular glands (goblet cells). Simple columnar epithelial cell Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action. Location: Nonciliated type lines most of the digestive tract (stomach to anal canal), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus. Basement membrane Photomicrograph: Simple columnar epithelium of the stomach mucosa (860 X). Figure 4. 3 c

(d) Pseudostratified columnar epithelium Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucussecreting cells and bear cilia. Cilia Mucus of mucous cell Pseudostratified epithelial layer Function: Secretion, particularly of mucus; propulsion of mucus by ciliary action. Location: Nonciliated type in male’s sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract. Trachea Photomicrograph: Pseudostratified ciliated columnar epithelium lining the human trachea (570 x). Basement membrane Figure 4. 3 d

Stratified Epithelium · Stratified squamous · Found as a protective covering where friction is common · Locations: Skin, Mouth, Esophagus oral cavity, throat, vagina, and anal canal · can accumulate keratin

Stratified Epithelium · Stratified cuboidal- ducts of mammary glands, sweat glands, salivary glands, and the pancreas · Stratified columnar · line vas deferens, male urethra, and part of pharynx · Rare in our body comparatively

Stratified Epithelium · Transitional epithelium · Both cube and elongated cells · Lines organs of the urinary system

Glandular Epithelium · Gland – one or more cells that secretes a particular product · Two major gland types · Endocrine gland · Ductless · Secretions are hormones · Exocrine gland · Empty through ducts to the epithelial surface · Include sweat and oil glands

Types of Glands

Unicellular Gland (Goblet Cell) Microvilli Secretory vesicles containing mucin Rough ER Golgi apparatus (a) Nucleus (b) Figure 4. 4

Connective Tissue · Found everywhere in the body · Functions · Binds body tissues together · Supports the body · Provides protection · store fat · produce blood cells · protect against infections · help repair tissue damage

Table 4. 1

Connective Tissue Characteristics · Variations in blood supply · Extracellular matrix · Non-living material that surrounds living cells (protein sugars water etc)

Extracellular Matrix · Two main elements · Ground substance – mostly water along with adhesion proteins and polysaccharide molecules · Proteoglycans Protein core + large polysaccharides (chrondroitin sulfate and hyaluronic acid) · Fibers · Produced by the cells · Three types · Collagen fibers · Elastic fibers · Reticular fibers

Connective Tissue Proper • Types: – Loose connective tissue • Areolar • Adipose • Reticular – Dense connective tissue • Dense regular • Dense irregular • Elastic

(a) Connective tissue proper: loose connective tissue, areolar Description: Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells. Elastic fibers Function: Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid. Collagen fibers Location: Widely distributed under epithelia of body, e. g. , forms lamina propria of mucous membranes; packages organs; surrounds capillaries. Fibroblast nuclei Epithelium Lamina propria Photomicrograph: Areolar connective tissue, a soft packaging tissue of the body (300 x). Figure 4. 8 a

(b) Connective tissue proper: loose connective tissue, adipose Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet. Function: Provides reserve food fuel; insulates against heat loss; supports and protects organs. Nucleus of fat cell Location: Under skin in the hypodermis; around kidneys and eyeballs; within abdomen; in breasts. Vacuole containing fat droplet Adipose tissue Mammary glands Photomicrograph: Adipose tissue from the subcutaneous layer under the skin (350 x). Figure 4. 8 b

(c) Connective tissue proper: loose connective tissue, reticular Description: Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network. Function: Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages. Location: Lymphoid organs (lymph nodes, bone marrow, and spleen). White blood cell (lymphocyte) Reticular fibers Spleen Photomicrograph: Dark-staining network of reticular connective tissue fibers forming the internal skeleton of the spleen (350 x). Figure 4. 8 c

(d) Connective tissue proper: dense connective tissue, dense regular Description: Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast. Collagen fibers Function: Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction. Location: Tendons, most ligaments, aponeuroses. Nuclei of fibroblasts Shoulder joint Ligament Photomicrograph: Dense regular connective tissue from a tendon (500 x). Tendon Figure 4. 8 d

(e) Connective tissue proper: dense connective tissue, dense irregular Description: Primarily irregularly arranged collagen fibers; some elastic fibers; major cell type is the fibroblast. Nuclei of fibroblasts Function: Able to withstand tension exerted in many directions; provides structural strength. Location: Fibrous capsules of organs and of joints; dermis of the skin; submucosa of digestive tract. Fibrous joint capsule Collagen fibers Photomicrograph: Dense irregular connective tissue from the dermis of the skin (400 x). Figure 4. 8 e

(f) Connective tissue proper: dense connective tissue, elastic Description: Dense regular connective tissue containing a high proportion of elastic fibers. Function: Allows recoil of tissue following stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration. Elastic fibers Location: Walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tubes. Aorta Heart Photomicrograph: Elastic connective tissue in the wall of the aorta (250 x). Figure 4. 8 f