exam 2

organ

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

fibrosis

-replacement of damaged cells with scar tissue

-Scar holds organs together, but does not restore function

-ex: repair of severe cuts and burns, scarring of lungs in tuberculosis

stages in healing of a skin wound 1

1)healing of a cut in the skin:

-severed vessels bleed into cut

-mast cells and damaged cells release histamine

-histamine dilates blood vessels and makes capillaries more permeable

2)blood plasma seeps into the wound carrying antibodies & clotting proteins

stages in healing of a skin wound 2

3)blood clot forms

-knits edges of cut together

-inhibits spread of pathogens

4)forms scab that temporarily seals wound and blocks infection

5)macrophages phagocytize and digest tissue debris

stages in healing of a skin wound 3

6)new capillaries sprout from nearby vessels

7)deeper portions of clot become infiltrated by capillaries and fibroblasts

-transform into soft mass called granulation tissue -macrophages remove the blood clot

-fibroblasts deposit new collagen

-begins 3–4 days after injury and lasts up to 2 weeks

stages in healing of a skin wound 4

8)epithelial cells around wound multiply and migrate beneath scab (tissue regenerates)

9)underlying connective tissue undergoes fibrosis

-scar tissue may or may not show through epithelium

10)remodeling (maturation) phase begins several weeks after injury and may last up to 2 years

atrophy

-shrinkage of a tissue through loss in cell size or number

-senile atrophy through normal aging

-disuse atrophy from lack of use

necrosis

pathological tissue death due to trauma, toxins, or infections

infarction

sudden death of tissue when blood supply is cut off

gangrene

tissue necrosis due to insufficient blood supply (usually involves infection)

Decubitus ulcer (bed sore or pressure sore)

form of dry gangrene where continual pressure on skin of immobilized patient cuts off blood flow

Dry gangrene

common complication of diabetes

Wet gangrene

liquefaction of internal organs with infection

Gas gangrene

usually from infection of soil bacterium that results in hydrogen bubbles in tissues

Apoptosis

-programmed cell death

-normal death of cells that have completed their function and best serve the body by dying and getting out of the way

-phagocytized by macrophages and other cells

-billions of cells die by apoptosis

-every cell has a built-in “suicide program”

Extracellular suicide

signal binds receptor protein in the plasma membrane called Fas

Fas activates enzymes

endonuclease chops up DNA and protease destroys proteins