Class Notes (839,291)
Canada (511,249)
BIOB32H3 (80)

tissues and histology.docx

5 Pages

Biological Sciences
Course Code
Kenneth Welch

This preview shows pages 1 and half of page 2. Sign up to view the full 5 pages of the document.
Tissues/Histolgy Tissues • Groups of cells similar in structure and function • The four types of tissues • Epithelial • Connective • Muscle • Nerve Epithelial Tissue • Cellularity – composed almost entirely of cells • Special contacts – form continuous sheets held together by tight junctions and desmosomes • Polarity – apical and basal surfaces • Supported by connective tissue – reticular and basal laminae • Avascular but innervated – contains no blood vessels but supplied by nerve fibers • Regenerative – rapidly replaces lost cells by cell division Classification of Epithelia • Simple or stratified • Squamous, cuboidal, or columnar 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 Epithelia: Simple Cuboidal • Single layer of cubelike 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 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 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) 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). Epithelia: Stratified Columnar • Several cell layers with cuboidal basal cells and columnar superficial cells • Functions in protection and secretion • Present in large ducts of some glands, and in portions of the male urethra 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 Glandular Epithelia • 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 Endocrine Glands • Ductless glands that produce hormones • Secretions include amino acids, proteins, glycoproteins, and steroids 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 Multicellular Exocrine Glands • Classified according to: • Simple or compound duct type • Structure of their secretory units 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) Connective Tissue • Found throughout the body; most abundant and widely distributed in primary tissues • Connective tissue proper • Cartilage • Bone • Blood Functions of Connective Tissue • Binding and support • Protection • Insulation • Transportation Characteristics of Connective Tissue • Connective tissues have: • Mesenchyme as their common tissue of origin • Varying degrees of vascularity • Nonliving extracellular matrix, consisting of ground substance and fibers Structural Elements of Connective Tissue • Ground substance – unstructured material that fills the space between cells • Fibers – collagen, elastic, or reticular • Cells – fibroblasts, chondroblasts, osteoblasts, and hematopoietic stem cells Ground Substance • Interstitial (tissue) fluid • Adhesion proteins – fibronectin and laminin • Proteoglycans – glycosaminoglycans (GAGs) • Functions as a molecular sieve through which nutrients diffuse between blood capillaries and cells Fibers • Collagen – tough; provides high tensile strength • Elastic – long, thin fibers that allow for stretch • Reticular – branched collagenous fibers that form delicate networks Connective Tissue: Fundamental Cell Type • Fibroblasts – connective tissue p
More Less
Unlock Document

Only pages 1 and half of page 2 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.