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BIOB32H3 Lecture Notes - Peristalsis, Ultimate Tensile Strength, Mesothelium

Biological Sciences
Course Code
Kenneth Welch

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Groups of cells similar in structure and function
The four types of tissues
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
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
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
Functions of Connective Tissue
Binding and support
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
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 proper
Chondroblasts cartilage
Osteoblasts bone
Hematopoietic stem cells blood
White blood cells (WBCs), plasma cells, macrophages, and mast cells
Connective Tissue (CT): Embryonic
Mesenchyme embryonic CT
Gel-like ground substance with fibers and star-shaped mesenchymal cells
Gives rise to all other connective tissues
Found in the embryo
Connective Tissue Proper: Loose
Areolar CT
Gel-like matrix with all three CT fibers
Fibroblasts, macrophages, mast cells, and some WBCs
Wraps and cushions organs
Widely distributed throughout the body
Connective Tissue Proper: Loose
Adipose CT
Matrix similar to areolar CT with closely packed adipocytes
Reserve food stores, insulates against heat loss, and supports and protects
Found under skin, around kidneys, within abdomen,
and in breasts
Connective Tissue Proper: Loose
Reticular CT
Loose ground substance with reticular fibers
Reticular cells lie in a fiber network
Forms a soft internal skeleton, or stroma, that supports other cell types
Found in lymph nodes, bone marrow, and the spleen
Connective Tissue Proper: Dense Regular
Parallel collagen fibers with a few elastic fibers
Major cell type is fibroblasts