Epithelium Flashcards
Four types of tissue
Nervous
Epithelial
Muscle
Connective
Steps for preparing tissue for light microscopy
1-Fixation- preserve tissue
2-Dehydration in graded concentrated ethyl alcohol- replace tissue water
3-Clearing in benzene, xylene or toluene- impregnate tissues with solvent
4-Embedding- paraffin @ 60c or plastic resin @ RT
-tissue more resistant to sectioning
3 basic steps for prep
Fixation
Sectioning
Staining
Stains
Eosin- stains +
Hematoxylin- stains -
Eosin
Stains cytoplasm, cytoplasmic filaments, collagen fibers, and basement membrane
Hematoxylin
Stains heterochromatin, nucleolus, the Rough ER, sulfated GAGs
H&E
used to distinguish nucleus from cytoplasm
Simple squamous distribution
- Lining of vessels
- Serous lining of cavities
- Pericardium
- Pleura
- Peritoneum
Simple squamous function
Facilitates movement
secretion
active transport- pinocytosis
Simple cuboidal distribution
Covering the ovary and thyroid
Simple cuboidal function
Covering and secretion
Simple columnar distribution
Lining of intestine and gallbladder
Simple columnar function
Protection, lubrication, absorption, secretion
Pseudostratified distribution
Lining of trachea, bronchi, nasal cavity
Pseudostratified function
Protection, secretion, cilia-mediated transport of particles trapped in mucus
Stratified squamous keratinized distribution
Epidermis
Stratified squamous keratinized function
Protection and prevent water loss
Stratified squamous nonkeratinized distribution
Mouth, esophagus, larynx, vagina, anal canal
Stratified squamous nonkeratinized function
Protection, secretion, prevent water loss
Stratified cuboidal distribution
Sweat glands, developing ovarian follicles
Stratified cuboidal function
Protection, secretion
Pseudostratified Transitional distribution
Bladder, ureters, renal calyces
Pseudostratified transitional function
Protection, distensibility
Stratified Columnar distribution
Conjunctiva
Stratified Columnar function
Protection
Epithelial cells in the digestive/respiratory/urinary system rest on
layer of connective tissue calls lamina propria
Basal lamina and basement membrane
Separation of epithelium from connective tissue
Basal lamina made up of
Type IV collagen
Laminin
Entactin
Proteoglycans
Can only be seen under EM
Basement membrane
Reticular fibers- type III collagen
Can be seen under light microscope
Hemidesmosomes
Help bind epithelial cells to the basal lamina
Striated border
Microvilli and glycocalyx found in small intestine
Brush border
Longer complex of microvilli found on proximal renal tubule
Sterocilia
Long
Nonmotile extensions of the apical suface
Cilia
Found on the apical surface of respiratory system
9+2 arrangement of microtubules
Myoepithelial cells
Found in secretory units of
- mammary
- sweat
- salivary glands
Endothelium
Simple squamous epithelium
-ling blood vessels and lymphatic vessels
Mesothelium
Simple squamous epithelium lining body cavities
-peritoneum
Epitheioid
Tissues that contain cells that are closely associated
-resembling an epithelium
Stem cells of the skin
Basal layer of the epidermis
Atrophy
death
Hypertrophy
increase in size
hyperplasia
increase in number
Dysplasia
change in orginization
metaplasia
transformation into another cell type
-respiratory cells can be transformed into stratified squamous epithelium
Thin and thick skin are distinguished by
the thickness of the epidermal layer
Thick skin
Found on the palms and soles
-lacks epidermal appendages– such as hair follicles and sebaceous glands
Stratum basale
Single layer of stem cells
-closest layer to connective tissue
Stratum spinosum
Mitotically active prickle cell layer
Stratum granulosum
Non-proliferating cells with stained granules
Stratum lucidum
clear layer seen only in thick skin!!
Stratum corneum
Keratinized cell ghosts
-top layer
Keratinocytes
Contain a lipid mix that is discharged to form the epidermal water layer
Melanocytes
Derived from neural crest cells
in stratum basale
# is the same in all races- skin color due to # and distribution of melanin granules in keratinocytes
Langerhans cells
Antigen-presenting cells
-derived from bone marrow
Component of SALT- skin associated lymphoid tissue
Merkel cells
epithelial tactile cells
- Mainly found in stratum basal
- More numerous in thick skin
- sensitive mechanoreceptor in areas such as fingertips
