Histology (Intro + Epithelial)

stem cells

unspecialized cells that don’t have any tissue-specific structures to perform specialized function, can differentiate into different specialized cells, and can endlessly divide way to replenish cells

stem cell types

embryonic stem cells, somatic/adult stem cells, and induced pluripotent stem cells (iPSCs)

in vitro fertilization

fertilizing eggs with sperm outside of the body

blastocyst

3-5 day old embryo, ball of cells that occurs after fertilization

cell-based therapies/regenerative or reparative medicine

medicine using stem cells to treat disease

proliferate/cell division

replication/division and renewing. if uncontrolled/abnormal, it can create cancer and other complications

differentiation

unspecialized stem cells goes through several stages to become more specialized at each step through different inducing conditions

somatic/adult stem cell

undifferentiated cell that stays in a stem cell niche, typically generate the cell types of the tissue they reside in, main purpose is to maintain and repair the surrounding tissue

embryonic stem cells

stem cells from embryos that can differentiate into many different cell types depending on the conditions thanks to being pluripotent

embryoid bodies

if embryonic stem cells clump together, they become this and start to differentiate spontaneously into many different cell types

directed differentiation

by changing the chemical composition of the culture medium, altering the surface of the culture dish, or modifying the cell by inserting specific genes, it’s possible to make embryonic stem cells into a specific cell type

brain 3 major cell types

astrocytes and oligodendrocytes (non-neuronal cells), and neurons (nerve cells)

induced pluripotent stem cells (iPSCs)

adult/somatic stem cells that have been genetically reprogrammed to a embryonic stem cell-like state

histology

the study of tissues

histogenesis

process of the primary germ layers (endoderm, ectoderm, and mesoderm) differentiating into different kinds of tissues

primary germ layers

endoderm, ectoderm, and mesoderm

endoderm

innermost germ layer

mesoderm

middle germ layer

ectoderm

outermost germ layer

tissue

group of similar cells that perform a common function, surrounded by/embedded in a non-living material called the matrix

matrix

non-living material that cells are embedded in

epithelial tissue

lines surfaces, glandular secretions

connective tissue

provides support and protection

muscle tissue

creates movement

nerve tissue

conducts impulse

membranous/serous epithelium

found in continuous sheets that are visceral (covers body structures) or parietal (lines body spaces), held together very tightly, have very little matrix

basement membrane

thin glue-like layer that attaches the non-free face of the epithelial sheet to underlying connective tissues, highly permeable to water and other substances that diffuse to the avascular epithelia

avascular

without vessels

membranous cell arrangements/layer types

simple, stratified, or psuedostratified

simple membranous cell arrangement/layer

only one layer

stratified membranous cell arrangement/layer

more than one layer

psuedostratified membranous cell arrangement/layer

one layer of varying heights

membranous cell shape types

squamous, cuboidal, columnar

squamous membranous cell shape

flat and sheet-like

cuboidal membranous cell shape

cube shaped, of equal width, length, and height

columnar membranous cell shape

tall and narrow

simple squamous epithelium

diffuses, filters, and secretes lubrication in the lung air sacs and the lining of the heart, blood vessels, and lymphatic vessels

simple cuboidal epithelium

secretes and absorbs in ducts and secretory portions of small glands and in kidney tubules

simple columnar epithelium

absorbs and secretes mucus and enzymes, in ciliated tissues in bronchi, uterine tubes, and uterus, and in smooth/unciliated tissues in the digestive tract and bladder

pseudostratified columnar epithelium

secretes mucus, ciliated tissues moves mucus in the ciliated tissue of the trachea, much of the upper respiratory tract, and some segments of the male reproductive tract

stratified squamous epithelium

protects against abrasion in the esophagus, mouth, and vagina

stratified cuboidal epithelium

protective tissue in the sweat glands, salivary glands, and the mammary glands

stratified columnar epithelium

secretes and protects in the male urethra and the ducts of some glands

transitional epithelium

allows the urinary organs to expand and stretch, lines the bladder, urethra, and ureters

endothelium

simple squamous epithelium that lines the lymphatic and blood vessels

mesothelium

simple squamous epithelium found on the surfaces of the pleura, pericardium, and peritoneum

goblet cells

secretes mucus that are propelled cilia, looks like a goblet

strata

means multiple layers

stratum corneum

most superficial layer, highly keratinized

keratin

water-proofing protein

hair papillae

bottom portion of hair, where the hair grows

hair root

portion of hair in the skin

hair shaft

portion of hair exposed outside of the skin

rugae

relaxed folds in the tissue that can stretch

glandular epithelium

forms the functional portions of exocrine glands (secretes into ducts) and endocrine/ductless glands (secretes into bloodstream)

exocrine glands

secretes into ducts

endocrine/ductless glands

secretes into bloodstream

follicles

spherical sacs

lumen

opening of the follicle

follicular cells

cells that reach the lumen of the follicle, produce hormones thyroxin and triiodothyronine

hormones produced by follicular cells

thyroxin and triiodothyronine that both regulate the rate of metabolism and affect body growth

parafollicular cells

cells not part of the follicle, produce calcitonin