organ
structure with discrete boundaries that is composed of 2 or more tissue types
histology
-microscope anatomy
-the study of tissues and how they are arranged into organs
tissue
a group of similar cells and cell products working together to perform a specific role in an organ
how do tissues differ from each other
-types and functions of their cells
-characteristics of the matrix
-relative amount of space occupied by cells vs matrix
matrix
-extracellular material
-composed of fibrous proteins & ground substance
ectoderm
-outer
-gives rise to epidermis and nervous sysytem
endoderm
-inner
-gives rise to mucous membrane lining digestive and respiratory tracts, digestive glands, among other things
mesoderm
-middle
-becomes gelatinous tissue called mesenchyme
-whispy collagem fibers and fibroblasts in gel matrix
-gives rise to cartilage, bone, blood, and muslce
longitudinal section
tissue cut on its long axis
cross section
-transverse section
-tissue cut perpendicular to long axis of organ
oblique section
tissue cut at angle between cross and longitudinal sections
smear
tissue is rubbed across a slide
spread
some membranes and cobwebby tissues are laid out on a slide
epithelial tissue
-sheets of closely adhering cells, one or more cells thick
-covers body surfaces and lines body cavities
-upper surface usually exposed to the environment or an internal space in the body
-constitutes most glands
-avasular
-almost no matrix
epithelial tissue functions
-protect depper tissues from injury and infection
-produce and release chemical secretions
-excrete waste
-absorb chemicals including nutrients
-selectively filter substances
-sense stimuli
basement membrane
-layer between an epithelium and underlying connective tissue
-collagen, reticular proteins, glycoproteins, other proteins (carbohydrate complexes)
-anchors the epithelium to the connective tissue below it
basal surface
surface of epithelial cell facing the basement membrane
apical surface
surface of epithelial cell that faces away from the basement membrane
simple epithelia
-contain one layer of cells
-named by shape of cells
-all cells touch basement membrane
stratified epithelia
-contain more than one layer
-named by shape of apical cells
-some cells rest on top of other and don’t touch basement membrane
goblet cells
wineglass-shaped mucus-secreting cells in simple columnar and pseudostratified epithelia
simple squamous epithelium
-sinlge row of thin cells
-permits rapid diffusion or transport of substances
-secretes serous fluid
-locations: alveoli, glomeruli, endothelium, and serosa
simple cuboidal epithelium
-single layer of square or round cells
-absorption and secretion, mucus production and movement
-locations: liver, thyroid, mammary and salivary glands, bronchioles, and kidney tubules
simple columnar epithelium
-single row of tall, narrow cells
-oval nuclei in basal half of cell
-brush border of microvilli, ciliated in some organs, may possess goblet cells
-absorption and secretion of mucus
-locations: lining of GI tract, uterus, kidney, and uterine tubes
pseudostratified epithelium
-looks multilayered, but all cells touch basement membrane
-nuclei at several layers
-has cilia and goblet cells
-secretes and propels mucus
-locations: respiratory tract and portions of male urethra
stratified epithelia
-deepest layers undergo continuous mitosis
-daughter cells push toward the surface and become flatter as they migrate upward
-finally die and flake off (exfoliation or desquamation)
keratinized
-found on skin surface
-abrasion resistant
nonkeratinized
lacks surface layer of dead cells
keratinized stratified squamous epithelium
-multiple cell layers; cells become flat and scaly toward surface
-resists abrasion; retards water loss through skin; resists penetration by pathogenic organisms
-locations: epidermis, palms and soles heavily keratinized
nonkeratinized stratified squamous epithelium
-same as keratinized epithelium w/o surface layer of deal cells
-resists abrasion and penetration of pathogens
-locations: tongue, oral mucosa, esophagus, and vagina
stratified cuboidal epithelium
-2 or more cell layers; surface cells square or round
-secretes sweat, produces sperm, produces ovarian hormones
-locations: sweat gland ducts, ovarian follicles, and seminiferous tubules
transitional epithelium
-multilayered epithelium with surface cells that change from round to flat when stretched
-allows for filling of urinary tract
-locations: ureter and bladder
cell junctions
-connections between 2 cells
-most cells are anchored to each other or their matrix
-cells communicate with each other, resist mechanical stress, and control what moves through the gaps between them
tight junction
-linkage between 2 adjacent cells by transmembrane cell-adhesion proteins
-in epithelia, they form a zone that completely encircles each cell near its apical pole
-seals off intercellular space, making it difficult for substance to pass between cells
-water proof velcro
desmosomes
-patch that holds cells together (like a clothing snap)
-keeps cells from pulling appart--resist mechanical stress
-hook-like, J-shaped proteins arise from cytoskeleton
-anchor cytoskeleton to membrane plaque
-transmembrane proteins from each cell joined by cell adhesion proteins
-allow for liquid to move, is more flexible
-loose
hemidesmosomes
-half desmosomes that anchor basal cells of an epithelium to underlying basement membrance
-epithelium can’t easily peel away from underlying tissues
gap (communicating) junction
-formed by ring-like connexons
-connexon consists of 6 transmembrane proteins arranged like segments of an orange around water-filled pore
-ions, nutrients, and other small solutes pass between cells
-located in cardiac and smooth muscle, embryonic tissue, lens and cornea
-cytoplasm can flow
gland
-cell or organ that secretes substances for use elsewhere in the body or releases them for elimination from the body
-usually composed of epithelial tissue in a connective tissue framework and capsule
secretion
product useful to the body
excretion
waste product
endocrine glands
have no ducts; secrete hormones directly into blood
hormones
-chemical messengers that stimulate cells elsewhere in the body
-ex: thyroid, adrenal, and pituitary glands
exocrine glands
-maintain their contact with surface of epithelium by way of a duct
-surface can be external (ex: sweat & tear glands) or internal (ex: pancreas & salivary glands)
-leave the body
unicellular glands
-found in an epithelium that is predominantly nonsecretory
-can be exocrine or endocrine
-ex: mucus-secreting goblet cells in tracea or endocrine cells of stomach
capsule
-connective tissue covering of exocrine gland
-boundary
septa or trabeculae
-extensions of capsule that divide interior of gland into compartments (lobes and lobules)
-either stratified squamous or dense regular connective tissue
stroma
-connective tissue framework of the gland
-supports and organizes glandular tissue
-framework
parenchyma
-cells that perform the tasks of synthesis and secretion
-typically cuboidal or simple columnar epithelium
-secretion
classification of glands
-duct shape
-gland shape
duct shape
-simple (unbranched, one tube)
-compound (branched, multiple tubes that come together)
tubular
narrow secretory portion
acinar
secretory cells form dilated sac (acinus or alveolus)
tubuloacinar
both tubular and acinar portions
serous glands
-produce thin, watery secretions
-ex: sweat, milk, tears, digestive juices
mucous glands
-produce glycoprotein, mucin, which absorbs water to form mucus
-goblet cells: unicellular mucous glands
mixed glands
contain both serous and mucous cell types and produce a mixture of the two types of secretions
apocrine secretion
-lipid droplet covered by membrane and cytoplasm buds from cell surface
-mode of milk fat secretion by mammary gland cells
merocrine secretion
-used by eccrine glands
-uses vesicles that release their secretion by exocytosis
-ex: tear glands, pancreas, gastric glands, serous glands
holocrine secretion
-cells accumulate a product until they disintegrate
-secrete a mixture of cell fragments and synthesized substances
-ex: oil glands of scalp and skin, and glands of eyelids
-high solid content/viscosity
membranes
may be only epithelial, only connective or a mix of epithelial, connective, and muscluar tissues
connective tissue membranes
dura mater, synovial membranes, periosteum
epithelial tissue membranes
anterior surface of cornea and lens of eye
cutaneous membrane
-the skin
-the largest membrane in the body
-stratified squamous epithelium (epidermis) resting on a layer of connective tissue (dermis)
-relatively dry layer serves protective function
-compound membrane (multiple tissue types)
mucous membrane (mucosa)
-lines passages that open to the external environment
-ex: digestive tract
-sublayers: epithelium, lamina propria (areolar tissue), muscularis mucosa (smooth muscle)
-absorptive, secretory, and protective functions
-often have mucus producing goblet cells
serous membrane (serosa)
-internal membrane
-simple squamous epithelium resting on a layer of areolar tissue
-produces serous fluid that arises from blood
-covers organs and lines walls of body cavities
-double membrane w/ watery sloution
endothelium
lines blood vessels and heart
mesothelium
lines body cavities (pericardium, peritoneum, and pleura)
viseral layer
against organ
parietal layer
against cavity
tissue growth
increasing the number of cells or size of existing cells
hyperplasia
growth through cell multiplication
hypertrophy
-enlargement of preexisting cells
-muscle growth through exercise
-accumulation of body fat
neoplasia
-development of a tumor (neoplasm)
-benign or malignant
-composed of abnormal, nonfunctional tissue
diferentiation
-development of more specialized form and function by inspecialized tissue
-ex: embryonic mesenchyme becoming cartilage and bone
metaplasia
-changing from one type of mature tissue to another
-Simple cuboidal tissue of vagina before puberty changes to stratified squamous after puberty
-Pseudostratified columnar epithelium of bronchi of smokers to stratified squamous epithelium
stem cells
-undifferentiated cells that are not yet performing any specialized function
-Have potential to differentiate into one or more types of mature functional cells
-in deepest layer of epidermis (stratum basale)
Developmental plasticity
ability of a stem cell to give rise to a diversity of mature cell types
totipotent
-have potential to develop into any type of fully differentiated human cell including accessory organs of pregnancy
-source: cells of very early embryo
pluripotent
-can develop into any type of cell in the embryo (but not accessory organs of pregnancy)
-source: cells of the inner cell mass of embryos (blastocyst)
Adult stem cells
-undifferentiated cells found in mature organs
-some are multipotent and some are unipotent
multipotent
able to develop into two or more cell lines (ex: bone marrow stem cells)
unipotent
produce only one cell type (ex: cells giving rise to sperm)
induced pluripotent stem cell (iPS Cell)
-start as a multipotent stem cell, reprogrammed to mimic a pluripotent stem cell
-bypasses ethical considerations of pluripotent stem cells
-performs like pluripotent stem cells
-possibility of genetically 100% compatible organ transplants feasible
regeneration
-replacement of dead or damaged cells by the same type of cell as before
-restores normal function
-ex: repair of minor skin or liver injuries
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