Epithelium Flashcards
Four basic types of tissues
- epithelial
- CT
- muscular tissue
- nervous tissue
Epithelial Tissue
- aggregated polyhedral cells
- very small amount of ECM
- line the surface of body cavities, glandular secretion
Connective Tissue
- several types of fixed and wandering cells
- abundant amount of ECM
- support and protection
Muscular Tissue
- elongated contractile cells
- moderate amount of ECM
- Movement
Nervous Tissue
- Intertwining cells with elongated processes
- no ECM
- Transmission of nervous impulses
Tissues form organs
two or more tissues combine to form functional units called organs
Parenchyma
cells responsible for main organ function
Stroma
supporting elements or matrix of the organ
Tissue prep
- fixation–preserves structural organization and hardens..10% formalin… cross links proteins to each other and to nucleic acids.
- Sectioning-steel blade on rotary microtome 3-10 micron sections and embedded in paraffin…which is removed prior to staining after it has been mounted on slide
- staining is used to localize and distinguish cell and tissue components
Eosin
- acidic dye
- Na+(dye)-
- acid radical has the dye
- stains cytoplasm, cytoplasmic filaments, collagen fibers and basement membrane, aa and proteins
- stained objects are eosinophilic
Hematoxylin
- “basic” dye
- basic radical has the dye
- stains heterochromatin (inactive, compact DNA), nucleolus, rough ER (RNA) and sulfated GAGs (neg charge)
- objects stained are basophilic
Epithelium
- closely coherent cells
- covering epithelia
- glandular epithelia
- derived from all 3 germ layers
Functions of Epithelium
-cover surfaces, provide protection, secrete and absorb various substances, and transport particles
Simple Squamous
- lining of vessels, serous lining of cavities, pericardium, pleura, peritoneum.
- facilitates movement of viscera, active transport by pinocytosis, sections of biologically active molecules
simple cuboidal
- covering of the ovary and thyroid
- covering and secretion
simple columnar
- lining of intestine and gal bladder
- protection, lubrication, absorption, secretion
pseudostratified columnar and cuboidal
- lining of trachea, bronchi, nasal cavity
- protection, secretion
- cilia mediated transport of particles trapped in mucous
pseudostratified transitional
- bladder, ureters, renal caylces
- protection, distensibility
stratified surface layer squamous keratinized
- epidermis
- protection and prevents water loss
stratified surface layer squamous nonkeratinized
- mouth, esophagus, larynx, vagina, anal canal
- protection, secretion, prevents water loss
stratified cuboidal
- sweat glands, developing ovarian follicles
- protection and secretion
stratified columnar
- conjunctiva
- Protection
epithelial cell morphology- general features
polyhedral in shape due to their packing in layers or in three dimensions.
- shapes are columnar, cuboidal, squamous
- shape of nucleus corresponds to shape of cell Most cells rest on CT.
Cuboidal cell and nucleus
round
cells have same height as width
columnar cell and nucleus
nucleus is oval, found near bottom of cell and perpendicular to basal lamina.
cell is taller than wide
apical surface often has cilia or microvilli
squamous cell and nucleus
flat cell and flat nucleus
Lamina propria
underlying layer of CT in the digestive, respiratory and urinary systems. small evaginations called papillae increase SA
Basal Lamina
- separated by CT from basal lamina.
- composed of type IV collagen, laminin, entactin, and proteoglycans. Anchoring fibrils made of type IV collagen attach basil laminae to CT. only visible with electron microscope
Basement Membrane
in some cells, reticular fibers (type III collagen) are associated with the basal lamina forming a reticular lamina, which associates with the basal lamina and is called the basement membrane
Intercellular Adhesion and Intercellular Junction
- cohesion of cells is important for their function
- cadherins and interdigitations of lateral membrane contribute to cohesion
- zonula occludens (permeability) and zonula adherens (in intestine), desmosomes and gap junctions. hemidesmosomes bind basal lamina to epithelial cells
Specialization of cell surface
- apical surface modified by increasing SA
- microvilli (1 micron high)
- cilia- much longer
Striated Border
intestinal epithelial cells, 1 micron
Brush border
proximal renal tubule
stereocilia
male reprotract
epididymis and vas deferens
cilia
apical surface of some cells in resp. system–9+2 arrangement of MT and covered by cell membrane. each cilia associated with basal body
classification of epithelia
- all have two names, some have 3
- 1st is number of cell layers
- 2nd is shape of superficial cells
- 3rd- if cilia or keratin is present
myoepithelium
branched contractile cells in secretory units of mammary, sweat, and salivary glands
endothelium
simple squamous epithelium lining blood and lymphatic vessels
mesothelium
simple squamous lining peritoneum
epitheliod
cells that are closely associated and resemble epithelium
Medical Applications
- epithelial cell renewal
- responses to stress
- atrophy, hypertrophy, hyperplasia (inc in #), dysplasia (org), metaplasia (change in cell type)
Skin
- heaviest organ (16% BW)
- Functions as :
- barrier
- sensory input
- immune input
- homeostasis
- endocrine and exocrine functions
- useful site for delivery of lipid soluble drugs
Composition of Skin
- epidermis that extends epidermal pegs or ridges downwards
- dermis that is a layer of CT that includes dermal papillae
- Hypodermis binds skin to underlying tissue
Thick and Thin skin
thickness of epidermal layer. thick on palms and soles, thin everywhere else. think has hair follicles and sebaceous glands.
Layers of Epidermis
Stratum basale (single layer of stem cells)
Stratum spinosum (mitotically active prickle cell)
Stratum granulosum (non-proliferating cells with stained granules
Stratum lucidum* (clear layer only in thick cells)
Stratum corneum- keratinized cell ghosts
*all different stages in the life of a keratinocyte
Keratinocytes
keratinizing epidermal cells that are the predominant cell type. Keratin is assembled into IF in the stratum basale and spinosum. Keratohyaline granules are synthesized in upper portion of spinous layer, which also produce lamellar bodies that contain lipids that are waterproof. old keratin cells make upper layer of epidermis for protection
Keratohyaline granules
dense, non membrane bound masses of filaggrin and other proteins associated with keratin.
Melanocytes
NCC origin
- melanin granules (from melanosomes) are passed into keratinocytes and account for pigment of skin (how fast they are synthesized by melanocyte and then phagocytosed by keratinocyte)
- number and distribution of granules determines skin color, the number of melanocytes is actually the same
Langerhans Cells
- antigen presenting cells from bone marror
- 2-8% od epidermal cells
- One component of Skin Associated Lymphoid Tissue (SALT)
- Unique in TEM- Birbeck granule
Merkel Cells
- found mainly in stratum basale of thick skin
- sensitive mechanoreceptor
- carcinomas are rare but hard to treat
junctions found on lateral border of intestinal epithelial cel
-tight, zonula adherens, desmosome, gap
lamellar bodies
contain lipid mixture that is waterproof
