Ch 4 - Histology Flashcards
What types of tissues are there?
Epithelial - Sheets of cells tightly packed together with little visible ECM. They line body surfaces/cavities, make up glands.
Connective Tissue - Connects all other tissues with good ECM with cells scattered thru them. They bind, support, protect, and allow for transport.
Muscle Tissue: Made of cells that contract and generate force, little ECM.
Nervous Tissue: Unique ECM and cells that generate, send. and receive messages (CNS, PNS, and Nerves)
What is ECM?
Extracellular Matrix. Made up of ground substances and protein fibers.
Ground Substance:
- Glycosaminoglycan (GAG): Long straight polysaccharides that are negative to attract positive ions.
- Proteoglycan Aggregate: GAGs with proteins as core, they are more firm and are barriers against diffusion.
- Glycoproteins: Cell adhesion molecules that help bind surface proteins, fibers, etc.
-ECM fluid: Stores ions, water, nutrients, and other solutes
Protein Fibers:
- Collagen: 20 types, often fibrous protein. Shaped like intertwined steel cable to resist pressure and tension. Look like white tendons.
- Reticular: Thin, collagen in the shape of scaffold/mesh and supports tissue or forms filter webs.
- Elastic: Can resist stretching (distensibility) and return back to normal shape (elasticity), surrounded by glycoproteins.
What are cell junctions?
Cell junctions are integral proteins in neighboring cells, there are three types
- Tight: Pulls together spaces between cells to be impermeable.
- Desmosomes: Increases resistance of tissue to mechanical stresses.
- Gap: Allow for small substances to move between them.
What are epithelial cells for? What are their main layers?
Protection, immune defenses, secretion, transport into other tissues (selective permeability), and sensation. However they do lack blood vessels and get nutrients via diffusion.
Apical surface, epithelium, then the basement layer of: Basal lamina is the ECM of the epithelial tissue and are formed by collagen fibers and ground substance; while the reticular lamina is the connective tissue, reticular fibers, and more ground substance.
What are the four types of simple epithelia?
Simple Squamous Epithelia: Single layer of flattened, centralized cells // Provides barrier for gas exchange and produces serous fluid // Air sacs of lungs, inner lining of body cavities and blood vessels, parts of kidney.
Simple Cuboidal Epithelia: Single layer of cubed, round-nuclei cells // Absorption, secretion of substances // Kidney tubules, lower respiratory passages, thyroid, salivary, and mammary glands.
Simple Columnar Epithelia: Single layer of rectangular cells that are ovoid, basal nuclei // Absorption, secretion, and propulsion of eggs // Digestive tract, uterine tube, gall bladder, and kidney tubules.
Pseudostratified Columnar Epithelia: Single layer of columnar cells with different heights, sometimes cilia // Secretes mucus and propels it with ciliary motion // Nasal cavity, male urethra, upper respiratory passages.
What are four types of STRATIFIED epithelia?
Stratified squamous epithelium:
- Keratinized: Dead, flaky, filled with keratin, cuboidal to squamous basal cells // Protects from mechanical stresses and prevents water loss // Epidermis
- Nonkeratinized: Living, cuboidal towards basal layers // Protects from mechanical stresses and microorganisms // Mouth, esophagus, vagina, anal canal.
Stratified cuboidal epithelium: Two or more cuboidal cells // Some secretion and absorption // Ducts of sweat glands
Stratified columnar epithelium: Two or more columnar cells // Protection, some secretion and absorption // Ducts of certain glands, conjunctiva, and male urethra.
Transitional epithelium: Dome shaped/flat (stretched) apical cells, with cuboidal basal cells. // Protects, gives distensibility // Urinary bladder, ureter, urethra.
What is a gland?
Structure that makes and secretes a product. Often made of epithelial cell in the underlying connective tissue.
- Exocrine glands: Releases secretions to apical surface to the body or hollow organ. Secretes thru duct lined with epithelial cells and are often local.
- Endocrine glands: Lacks ducts and secretes products directly into blood.
