Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings AIM: How are tissues categorized? Do Now: Homework: Read chapter 4, do homework questions. Due at end of week. QUIZ – tomorrow (Cells Organelles, Mitosis, Protein Synthesis)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 4: Tissues The Living Fabric

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Tissues  Histology – study of tissues  Cell specialization allows body to function in sophisticated ways  Hazard of specialization – if particular group of cells die off or are injured, it can severely disable / destroy the body.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Tissues  Tissues = Groups of cells similar in structure and function  The four primary types of tissues  Epithelial (covering)  Connective (support)  Muscle (movement)  Nerve (control)  Tissues are organized into organs (usually containing all four types of tissues)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelial Tissue  Epithelial Tissue (Epithelium) – sheet of cells that cover body surface or lines a body cavity. Occurs in: 1. Covering and lining epithelium 2. Glandular epithelium  Epithelium form boundaries between environments  Example: skin, urinary bladder  Functions include: 1. Protection – mechanical & chemical injury; bacterial invasion (skin) 2. Absorption – digestive tract 3. Filtration - kidney 4. Excretion - kidneys 5. Secretion - kidney 6. Sensory Reception - skin

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Special Characteristics of Epithelial Tissue  Cellularity – composed almost entirely of cells (CT not cells) 1.Polarity – epithelial cells have:  Apical (upper) surface – exposed to body exterior or cavity of internal organ, and  May have microvilli (brush border) or cilia  Basal surfaces – lower, attached portion  Apical and basal surface of cell have different structure and function 2.Specialized Contacts – epithelium fit close together forming continuous sheets – tight junctions and desmosomes. 3.Supported by Connective Tissue – epithelium rest upon and supported by connective tissue (CT). 4.Avascular but innervated – contains no blood vessels but supplied by nerve fibers – nourished from blood vessels in underlying CT 5.Regenerative – rapidly replaces lost cells by cell division – damage from friction or substances like bacteria, acid or smoke.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelial Tissue  Basement Membrane – reinforces epithelial sheet (stretching/tearing forces) 1. Basal lamina - noncellular and mostly made of glycoproteins (secreted from epithelium)  Selective filter for what may enter epithelium from underlying CT 2. Reticular Lamina – just under basal lamina – this layer of extracellular material containing a network of collagen protein fibers (“belonging to underlying CT”)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Classification of Epithelia 1. Simple 2. Stratified Figure 4.1a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Classification of Epithelia 1. Squamous 2. Cuboidal 3. Columnar Figure 4.1b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Simple Squamous  Single layer of flattened cells with disc-shaped nuclei and sparse cytoplasm  Functions  Diffusion and filtration  Provide a slick, friction-reducing lining in lymphatic and cardiovascular systems  Present in the kidney glomeruli, lining of heart, blood vessels, lymphatic vessels, and serosae

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Simple Squamous Figure 4.2a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Simple Cuboidal  Single layer of cube-like cells with large, spherical central nuclei  Function in secretion and absorption  Present in kidney tubules, ducts and secretory portions of small glands, and ovary surface

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Simple Cuboidal Figure 4.2b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Simple Columnar  Single layer of tall cells with oval nuclei; many contain cilia  Goblet cells are often found in this layer  Function in absorption and secretion  Nonciliated type line digestive tract and gallbladder  Ciliated type line small bronchi, uterine tubes, and some regions of the uterus  Cilia help move substances through internal passageways

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Simple Columnar Figure 4.2c

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Pseudostratified Columnar  Single layer of cells with different heights; some do not reach the free surface  Nuclei are seen at different layers  Function in secretion and propulsion of mucus  Present in the male sperm-carrying ducts (nonciliated) and trachea (ciliated)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Pseudostratified Columnar Figure 4.2d

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Stratified Squamous  Thick membrane composed of several layers of cells  Function in protection of underlying areas subjected to abrasion  Forms the external part of the skin’s epidermis (keratinized cells), and linings of the esophagus, mouth, and vagina (nonkeratinized cells)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Stratified Squamous Figure 4.2e

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Stratified Cuboidal and Columnar  Stratified cuboidal  Quite rare in the body  Found in some sweat and mammary glands  Typically two cell layers thick

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Stratified Columnar  Stratified columnar  Limited distribution in the body  Found in the pharynx, male urethra, and lining some glandular ducts  Also occurs at transition areas between two other types of epithelia

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Transitional  Several cell layers, basal cells are cuboidal, surface cells are dome shaped  Stretches to permit the distension of the urinary bladder  Lines the urinary bladder, ureters, and part of the urethra

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Transitional Figure 4.2f

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epithelia: Glandular  A gland is one or more cells that makes and secretes an aqueous fluid  Classified by:  Site of product release – endocrine or exocrine  Relative number of cells forming the gland – unicellular or multicellular

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Endocrine Glands  Ductless glands that produce hormones  Secretions include amino acids, proteins, glycoproteins, and steroids

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Exocrine Glands  More numerous than endocrine glands  Secrete their products onto body surfaces (skin) or into body cavities  Examples include mucous, sweat, oil, and salivary glands  The only important unicellular gland is the goblet cell  Multicellular exocrine glands are composed of a duct and secretory unit

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Multicellular Exocrine Glands  Classified according to:  Simple or compound duct type  Structure of their secretory units

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Goblet Cell Figure 4.3b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Structural Classification of Multicellular Exocrine Glands Figure 4.4a–d

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Structural Classification of Multicellular Exocrine Glands Figure 4.4e–g

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Modes of Secretion  Merocrine – products are secreted by exocytosis (e.g., pancreas, sweat, and salivary glands)  Holocrine – products are secreted by the rupture of gland cells (e.g., sebaceous glands)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Modes of Secretion Figure 4.5