First Quiz. Copyright 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Transcription

1 First Quiz

2 First Hour Exam is next Monday!!!

3 Introduction to Tissues Histology is the study of tissues Individual body cells are specialized w/ each cell type performing specific functions that maintain homeostasis Tissues are cells that are similar in structure and perform a common/related function

4 Tissues The four types of tissues Epithelial Connective Muscle Nerve Tissues are organized into organs w/ most organs containing all 4 types of tissue

5 Epithelial Tissue Epithelium is a sheet of cells that covers a body surface or lines a body cavity. It occurs in the body as: 1) Covering/lining epithelium 2) Glandular epithelium

6 Epithelial Tissue 1) Covering lining epithelium: Forms the outer layer of the skin, lines the open cavities of the cardiovascular, digestive & respiratory systems, and covers the walls and organs of the ventral body cavity. 2) Glandular epithelium: Fashions the glands

7 Epithelial Tissue Epithelia form boundaries between different environments. E.g. Epithelium of the urinary bladder separates underlying cells of the bladder wall from urine. In this role, it functions are: 1) Protection 2) Absorption 3) Filtration 4) Excretion 5) Secretion 6) Sensory Reception

8 Epithelial Tissue: Special Characteristics 1) Special contacts form continuous sheets held together by tight junctions and desmosomes 2) Polarity apical and basal surfaces

9 Epithelial Tissue 3) Supported by connective tissue Basement Membrane is composed of: reticular lamina: collagen basal lamina: glycoproteins 4) Avascular but innervated contains no blood vessels but supplied by nerve fibers 5) Regenerative rapidly replaces lost cells by cell division

10 Classification of Epithelia Simple Epithelia: Single cell layer Found where absorption / filtration occurs Stratified Epithelia: -2 or more cell layers -found in high abrasion areas Figure 4.1a

11 Classification of Epithelia In cross-section (c.s.), epithelial cells have 6 sides This polyhedron shape allows for tight packing

12 Classification of Epithelia Epithelial cells vary in height: Three types: Squamous cells: flat Cuboidal cells: cube-like Columnar: Column-like The shape of the nucleus conforms to the shape of the cell Figure 4.1b

13 Simple 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

14 Simple Epithelia : Simple Squamous Figure 4.2a

15 Simple 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

16 Simple Epithelia : Simple Cuboidal Figure 4.2b

17 Simple Epithelia : Simple Columnar Single layer of tall cells with oval nuclei; many contain cilia on the free surface 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

18 Simple Epithelia : Simple Columnar Figure 4.2c

19 Simple Epithelia : Pseudostratified Columnar Single layer of cells with different heights; some do not reach the free surface Gives the false impression that several cell layers are present Nuclei are seen at different layers Function in secretion and propulsion of mucus Present in the male sperm-carrying ducts (nonciliated) and trachea (ciliated)

20 Simple Epithelia : Pseudostratified Columnar Figure 4.2d

21 Stratified Epithelia Thick membrane composed of 2 or more layers of cells Basal cells divide and push apically to replace older surface cells Function in protection of underlying areas subjected to abrasion

22 Stratified Epithelia: Stratified Squamous Most widespread Free surface is squamous while the deeper layers are cuboidal or columnar Located in high wear areas Forms the external part of the skin s epidermis (keratinized cells), and linings of the esophagus, mouth, and vagina (nonkeratinized cells)

23 Epithelia: Stratified Squamous Figure 4.2e

24 Stratified Epithelia : Stratified Cuboidal and Columnar Stratified cuboidal Quite rare in the body Found in some sweat and mammary glands Typically two cell layers thick

25 Stratified Epithelia : Stratified Cuboidal and 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

26 Stratified Epithelia : Transitional Several cell layers, basal cells are cuboidal, surface cells are dome shaped Stretches to permit the distension of the urinary bladder When distended w/ urine, the layer thins from 6 cells to 3 cells Lines the urinary bladder, ureters, and part of the urethra

27 Epithelia: Transitional Figure 4.2f

28 Epithelia: Glandular A gland is one or more cells that makes and secretes an aqueous fluid A secretion can be water based, lipid based and/or steroid based Classified by: Site of product release endocrine or exocrine Relative number of cells forming the gland unicellular or multicellular Unicellular gland: scattered within epithelial sheets Multicellular gland: form by invagination or evagination from an epithelial sheet and possesses ducts

29 Endocrine Glands Ductless glands that produce hormones Secretions include amino acids, proteins, glycoproteins, and steroids Secreted by exocytosis directly into the extracellular space where the hormones enter the blood and travel to specific target organs

30 Exocrine Glands More numerous than endocrine glands Secrete their products onto body surfaces (skin) or into body cavities either by exocytosis (unicellular glands) or via ducts (multicellular glands) Examples include mucous, sweat, oil, and salivary glands

31 Unicellular Exocrine Glands E.g. goblet cell Epithelial lining of the intestinal & respiratory tracts amid columnar cells Produce mucin, a complex glycoprotein that dissolves in water to form mucus

32 Goblet Cell Figure 4.3b

33 Multicellular Exocrine Glands Classified according to: Simple or compound duct type Structure of their secretory units Supportive connective tissue surrounds the secretory cells supplying it w/ blood vessels, nerve fibers, forming a fibrous capsule dividing the gland into lobes

34 Multicellular Exocrine Glands Based on the duct structure, Multicellular Exocrine Glands are either simple or compound glands Simple glands have unbranched ducts Compound glands have branched ducts

35 Multicellular Exocrine Glands Multicellular Exocrine Glands are further categorized by their secretory units 1) tubular: secretory cells form tubes 2) alveolar: secretory cells form sacs 3) tubuloalveolar: secretory cells form tubes & sacs

36 Structural Classification of Multicellular Exocrine Glands Figure 4.4a d

37 Structural Classification of Multicellular Exocrine Glands Figure 4.4e g