exam 2 Flashcards
1
Q
cells
A
simplest structural & functional unit of life
-arise from other cells
-all organisms composed of cells & cell products
-organism’s structure & functions due to cellular activity
-exhibit biochemical unity
-shape & size are diverse
2
Q
TEM
A
-views cell’s ultrastructure
-high magnification & resolution
-resolution=5 nm
3
Q
SEM
A
-3D images but only view surface features
4
Q
LM
A
-resolution=200 nm
-human eye resolution=70-100 um
5
Q
cytosol/intracellular fluid
A
gel-like solution
6
Q
extracellular fluid
A
fluid outside of cell
7
Q
PM
A
defines boundaries of cell
-intracellular face=side that faces cytoplasm
-extracellular face=side that faces outside
8
Q
lipid components of PM
A
-phospholipids: make up 75% of lipids; arranged in bilayer w polar heads facing outside & hydrophilic tails facing inside
-cholesterol: 20% of lipids
-glycolipids: 5%; forms glycocalyx
9
Q
proteins of PM
A
-make up 50% of PM weight
-transmembrane proteins span bilayer (mostly glycoproteins w oligosaccharides facing extracellular side; drift about freely or anchored to cytoskeleton)
-peripheral proteins adhere to one face of PM & associated w transmembrane proteins
10
Q
membrane protein functions
A
-receptors that messengers can attach to
-second-messenger systems (binding of signaling molecule causes release of second molecule in cytoplasm; important to hormone & neurotransmitter action)
11
Q
enzymes
A
catalyze chemical reaction at cell surface
12
Q
ion channels
A
allow water & dissolved ions to pass through PM
-gated=open & close to stimulus
-ligand-regulated gates respond to chemical messengers
-voltage-regulated gates respond to changes in electrical potential
-mechanically regulated gates respond to physical changes such as stretch & pressure
13
Q
carriers
A
bind target molecules & take them across PM
-exhibit specificity for particular solute
-exhibit saturation (all carriers filled w ligands, giving transport max rate)
-pumps=carriers that use ATP
14
Q
glycoproteins
A
cell-identity markers allowing recognition of cell as “self”
-all animal cells have glycocalyx external to PM
-human blood types determined by glycolipids
15
Q
cell-adhesion molecules
A
hold cells to one another
16
Q
surface extensions of cells
A
-microvilli: increase SA; dense & appear as brush border
-cilia: hairlike processes that serve sensory or motile functions; every human cell has single, nonmotile primary cilium few micrometers long
-flagella: whiplike structures longer than cilia; only on sperm cells in humans
17
Q
filtration
A
process by which particles are driven through PM by hydrostatic pressure
-blood capillaries (materials forced through gaps by blood pressure)
-kidneys filter waste materials from blood
18
Q
simple diffusion
A
net movement of particles from areas of high to low concentration, moving down conc gradient
-rates based on five factors: temp (high temp=faster rate); weight (more weight=slower rate); gradient (steep gradient=faster rate); SA (high SA=faster rate); permeability (high permeability=faster rate; adjust permeability by adding/removing membrane channels)
19
Q
osmosis
A
diffusion of water down conc gradient through selectively permeable membrane
-moves from more dilute to more concentrated solution (more water to less water)
-water enters cells through aquaporins
-solution w nonpermeating molecules on one side causes water to cross towards that side (water level falls on side w permeating molecules & rises on nonpermeating side; levels become stable when osmotic pressure on both sides in balance)
-reverse osmosis, water forced through membrane under pressure against conc gradient
20
Q
osmole
A
used to measure osmotic conc of body fluids
-osmolality=number of osmoles per kg of water
-osmolarity=number of osmoles per liter of solution
-physiological conc measured in milliosmoles per liter (mOsm/L)
21
Q
tonicity
A
ability of solution to affect fluid volume & pressure in cell
22
Q
hypotonic solution
A
lower conc of nonpermeating solutes than in intracellular fluid
-water moves into cell
23
Q
hypertonic solution
A
higher conc of nonpermeating solutes than in intracellular fluid
-water moves out of cell
24
Q
isotonic solution
A
total conc of nonpermeating solutes equal to that of intracellular fluid
-equal amounts of water flows into & out of cell
25
uniports
carry one solute at a time
26
symports/co-transport
carry two or more solutes in same direction
27
antiports/counter-transport
carry two or more solutes in opposite directions
28
facilitated diffusion
carrier-mediated transport that moves solute down conc gradient
-no ATP
29
primary active transport
carrier-mediated transport that moves solute against conc gradient
-ATP
-Na+/K+ pump (each cycle of pump hydrolyzes one ATP & exchanges 3 Na for 2 K)
30
vesicular transport
moves large particles, droplets of fluid, or numerous molecules through PM in vesicles
31
endocytosis
brings materials into cell
-employ motor proteins powered by ATP
32
exocytosis
process of discharging material from cell, occurs in many cells that secrete hormones or enzymes
-vesicle containing material to be discharged merges w cell membrane, releasing it to extracellular space
-employ motor proteins powered by ATP
33
receptor-mediated endocytosis
selective process by which cells take in specific molecules w minimum of unnecessary fluid
-receptors bind to particles from ECF & cluster together
-membrane sinks in & pit becomes coated inside cell w protein clathrin which buds off into cells as vesicle
-LDL (cholesterol)
34
phagocytosis
process by which cells engulf particles
-neutrophils=WBCs that phagocytize bacteria by extending pseudopods & trapping bacteria in phagosome which is merged w lysosome that contain enzymes to destroy invader
35
pinocytosis
process of taking in droplets of ECF containing useful molecules
-pits form in cell membrane & separate from membrane, forming membrane-bound pinocytotic vesicles inside cell
36
cytoskeleton
collection of protein filaments & cylinders that structurally support cell, determine its shape, organize its content, move substance through cell, & contribute to movement of entire cell
37
microfilaments
thin (6 nm); made of actin, forming network on inside of PM called membrane skeleton
38
intermediate filaments
8-10 nm; resist stress & participate in cell junctions
-composed of keratin in epidermal cells
39
microtubules
25 nm; made of tubulin
-radiate from centrosome & hold organelles in place, form structural bundles, guide organelles & molecules, & form axonemes of cilia & flagella
-forms mitotic spindle that guides chromosomes during cell division
40
organelles
internal structures in cells that carry out specialized metabolic tasks
41
nucleus
largest organelle; control center (contains genetic info)
-most cells = one nucleus (RBCs = none & skeletal muscle = multiple)
-enclosed by nuclear envelope that's perforated w nuclear pores
-nuceloplasm=material in nucleus including chromatin & nucleolus
42
ER
system of interconnected cisternae enclosed by single membrane
43
rough ER
flattened sac covered w ribosomes
-synthesizes phospholipids & proteins of PM & proteins that are packaged in other organelles or secreted from cell
44
smooth ER
more tubular cisternae & lacks ribosomes
-alcohol & drug detoxification
-manufactures steroid hormones
-stores calcium in muscle cells
45
ribosomes
small granules of protein & RNA that translate mRNA into protein
46
Golgi apparatus
system of cisternae
-synthesizes & adds carb moieties to proteins prior to packaging
-receives completed proteins from rough ER, sorts them, & packages them into Golgi vesicles
-secretory vesicles that store cell product
47
lysosomes
packages of enzymes surrounded by membrane
-hydrolyze proteins & nucleic acids
-aid in digestion of phagocytized bacteria, nonvital organelles, & surplus cells
48
peroxisomes
resemble lysosomes; produced in ER
-use oxygen to oxidize organic molecules, producing hydrogen peroxide that's used to oxidize other molecules
49
proteasomes
protein complexes responsible for degrading proteins tagged for destruction
50
mitochondria
specialized to synthesize ATP (powerhouse of cell)
-double membrane (inner membrane=cristae)
-matrix (between cristae) contains ribosomes, enzymes, & mtDNA
51
centriole
short cylindrical assembly of microtubules arranged in 9 groups of 3
-2 centrioles lie perpendicular to each other in centrosome
-plays role in cell division
52
inclusions
-stored cellular products: glycogen granules
-foreign bodies: viruses, intracellular bacteria, dust particles
-never enclosed by membrane
53
pyrimidines
C, T, U
54
purines
A, G
55
complementary base pairing
A&T forms 2 H-bonds; C&G forms 3 H-bonds
56
DNA function
code for proteins a cell makes
57
chromatin
DNA complexed w proteins
-46 chromosomes
-2 m in length if fully unwound
-stored in nucleus
-nucleosomes (consists of core particle that's disc-shaped of 8 proteins called histones wrapped around DNA & linker DNA)
-chromosome territory: chromosome packed into its own region of nucleus permeated w channels
58
RNA vs DNA
-RNA smaller than DNA (tRNA=70-90 bases; mRNA=10,000 bases; DNA=100 million bases)
-single-stranded
-ribose sugar not deoxyribose
-uracil not thymine
-RNA function=interpret code in DNA & direct synthesis of proteins
59
gene
information-containing segment of DNA that codes for production of RNA molecule
60
genome
all the DNA in one 23-chromosome set
61
genetic code
system that enables 4 nucleotides to code for AA sequences of all proteins
-3 nucleotides per AA makes codon contained by mRNA
-max of 64 codons (some AA specified by more than one codon)
-start codon (Met) & stop codon
62
transcription
process by which DNA is made into RNA
-RNA polymerase: binds to DNA & assembles RNA strand
-promoters=start
-enzyme opens DNA helix, reads bases in one strand, & forms complementary bases
-terminator=stop
-produces pre-mRNA that contains exons & introns (enzymes remove introns & splice exons together; modified at 5' end by adding G-cap that protects from degradation & helps ribosome recognize start site on mRNA; polyA tail added to 3' end)
63
translation
process by which mRNA is made into proteins
-protein cap=start
-tRNA w anticodon on one end & binding site for AA on other side
-ribosomes w two subunits composed of rRNA & enzymes (two subunits come together; A, P, & E sites where tRNAs bind)
64
DNA replication
accomplished through complementary base pairing
-unwind double helix from histones
-DNA polymerase matches exposed bases w complementary free nucleotides (two strands copied by separate DNA polymerases moving in opposite directions; two new daughter strands made w each daughter DNA consisting of one old & new strand- semiconservative replication)
65
G1 phase
-synthesize proteins, grows, & carries out its tasks in support of body
-accumulate materials needed to replicate DNA
66
S phase/DNA replication
makes duplicate copy of centrioles & nuclear DNA
67
G2 phase
finishes replicating centrioles & synthesizes enzymes that control cell division
-checks for error
68
cell cycle length
-skin cells=rapid
-bone cells=slow
-skeletal muscle & nerve cells=no time
69
G0 phase
cells that cease to divide
-inability to stop cycling & enter G0 common in cancer cells
70
prophase
period where chromosome shorten & thicken, becoming compact rods that align in middle of cell
-nuclear envelope disintegrates & chromosomes released into cytosol
-centrioles sprout spindle fibers that push centrioles apart
-spindle fibers attach to kinetochore on each side of centromere
71
metaphase
period where chromosomes, anchored by mitotic spindle, wait for signal to split apart
72
anaphase
cleaving of centromere of each chromatid pair, forming sister chromatids
-daughter chromosomes migrate to opposite poles by motor proteins in kinetochore crawling on spindle fiber
-sister chromatids=genetically identical
73
telophase
sister chromatids clustered on each side of cell
-new nuclear envelope forms & chromosome uncoil while mitotic spindle vanishes
74
cytokinesis
overlaps telophase; cytoplasmic division into two new cells
-myosin pulls on actin microfilaments, creating cleavage furrow
-parent cell pinches in two as furrow is deepened
-daughter cells enter interphase
75
tissues
group of similar cells that arise from same region of embryo & work together to perform specific role
76
human development
begins w fertilized egg which divides to produce identical, smaller cells
-first tissues organized into 3 strata called primary germ layers
77
ectoderm
outer layer that gives rise to epidermis & nervous system
78
endoderm
inner layer that gives rise to mucous membranes of digestive & respiratory tracts & to digestive glands
79
mesoderm
middle layer that becomes mesenchyme, giving rise to muscle, bone, & blood
80
epithelium
covers body surface, lines body cavities, forms external & internal linings of organs, & constitutes most gland tissue
-lies on layer of loose CT & dependent of tissue's blood supply for nutrients & waste removal
81
simple epithelium
one cell layer where every cell touches basement membrane
-squamous (thin, scaly)
-cuboidal (squarish, round)
-columnar (tall, narrow; produce mucus that's secreted by goblet cells)
-pseudostratified columnar (all cells contact basement membrane but not all reach apical surface; produce mucus that's secreted by goblet cells)
82
stratified epithelium
two or more layers where only basal layer contacts basement membrane
-squamous, cuboidal, columnar (rare)
-transitional (transitional stage between squamous & columnar)
83
stratified squamous epithelium
-deepest layers=cuboidal to columnar & undergo continual mitosis
-daughter cells pushed toward surface & become flatter (scalier)
-cells migrate to surface where they die & flake off (exfoliation/desquamation)
84
keratinized stratified squamous epithelium
found on skin surface; covered w layer of compact, dead squamous cells packed w keratin & coated w water repellant glycolipid
85
nonkeratinized stratified squamous epithelium
lacks surface layer of dead cells; found on tongue, esophagus, vagina, & other internal membranes
86
transitional epithelium
limited to urinary tract; umbrella cells w thick outer phospholipid layer w dense patches of lipid rafts (uroplakins that are impermeable to urine embedded in rafts)
87
cell junctions
connections between cells
-enable cells to resist mechanical stress, communicate, & control movement of substances through gaps between cells
88
tight junction
completely encircles epithelial cell near apical surface & joins it tightly to neighboring cells
-transmembrane cell-adhesion proteins link adjacent cells & seal off intercellular space preventing substances from passing between cells
89
desmosome
patch that holds cells together
-keep cells from pulling apart but don't prevent substances from passing between cells
-common in epidermis & cardiac muscle
90
hemidesmosome
links basal cells of epithelium to basement membrane
91
gap junction
formed by connexon
-each connexon consists of ring of 6 transmembrane proteins surrounded central water-filled channel (allow ions, glucose, & solutes to pass from cell to another)
-found in intercalated discs of cardiac muscle & smooth muscle
92
glands
cells or organs that secrete substances for use elsewhere or for elimination
-product=secretion if useful to body OR excretion if waste product
93
exocrine glands
maintain contact w surface through ducts
-enclosed in fibrous capsule w septa/trabeculae that divide gland into lobes
-simple=single unbranched duct
-compound=branched ducts
-tubular=duct & secretory portions of uniform diameter
-acinar=secretory cells that form dilated sac
-tubuloacinar=tubules & acini
-sweat, mammary, lacrimal, salivary, liver & pancreas
94
endocrine glands
lack ducts & secrete products into blood via capillaries
-secretions=hormones that function as chemical messengers that act on cells elsewhere in body
-pituitary, thyroid, adrenal glands
95
unicellular glands
secretory cells found in epithelium that lack ducts
-goblet cells of respiratory system that secrete mucus
96
mucous glands
secrete glycoprotein, mucin, which absorbs water once secreted to form mucus
-goblet cells
97
merocrine (eccrine) glands
release products by exocytosis
-lacrimal
-sweat glands
98
apocrine glands
lipid droplets combine in cytosol & bud from cell surface
99
holocrine glands
accumulate product in their cells & then disintegrate to release product
-sebaceous
100
functions of connective tissue
-binding of organs (tendons=muscle to bone & ligaments=bone to bone)
-support
-physical protection
-immune protection
-movement
-storage
-heat production
-transport
101
fibroblasts
large flat cells that produce fibers & ground substance of tissue
102
macrophages
large phagocytic cells that engulf & destroy bacteria, foreign particles, & dead/dying cells & respond to antigens
103
leukocytes
enter CT from bloodstream & wander in search of bacteria
104
plasma
synthesize antibodies
105
mast cells
located near blood vessels & secrete heparin & histamine
106
adipocytes
fat cells that occur in small clusters
-main cell type in adipose tissue
107
collagen fibers
made of collagen
-tough, flexible, & resist stretching
-white fibers
108
reticular fibers
thin collagen fibers coated w glycoprotein, forming spongelike framework in some organs
109
elastic fibers
made of elastin which recoil from stretching
110
ground substance
occupies space between cells & fibers
-Glycosaminoglycan (GAGs): long polysaccharide made of amino sugars & uronic acid that's able to absorb & hold water (chondroitin sulfate, heparin, & hyaluronic acid)
-proteoglycans: central core of protein & bristle-like outgrowths of GAGs that form thick colloids & create strong structural bonds between cells & extracellular macromolecules
-glycoproteins: bind PM proteins to collagen & proteoglycans outside of cell, holding tissues together
111
cell body/neurosoma
contains nucleus & other organelles
-center of genetic control & protein synthesis
112
dendrites
short, branched processes extending from cell body that receive signals from other cells
113
axon/nerve fiber
conducts outgoing signals from cell body to nerve cells
114
neurons
detect stimuli, respond, & transmit information rapidly
115
glial cells
outnumber neurons & make up most of volume of nervous tissue, providing support, protection, & maintenance of neurons
116
cutaneous membrane/skin
consist of keratinized stratified squamous epithelium resting on underlying CT
117
mucous membrane/mucosa
lines passageways open to external environment
-digestive, respiratory, urinary, & reproductive tracts
-consist of epithelium, areolar CT called lamina propria, & smooth muscle called muscularis mucosae
-covered w mucus that traps bacteria & foreign particles, preventing them from invading body
118
serous membrane/serosa
lines insides of body cavities
-pleura, pericardium, peritoneum
-simple squamous epithelium resting on thin layer of CT
-produce watery serous fluid similar to blood serum
-epithelial content=mesothelium
119
synovial membrane
lines some joints
-made of areolar CT & squamous epithelium w no basement membrane
-produce synovial fluid that reduces friction
120
hyperplasia
tissue growth through cell multiplication
121
hypertrophy
enlargement of preexisting cells
122
neoplasia
development of tumor composed of abnormal, nonfunctional tissue
123
differentiation
process of change from unspecialized tissue to more specialized mature tissues
124
metaplasia
change from one type of mature epithelium into another
-during puberty, vaginal lining changes from simple cuboidal to stratified squamous
125
stem cells
undifferentiated cells that have potential to change into one or more types of mature functional cells
126
embryonic stem cells
compose early human embryo
-totipotent: develops into any type of human cell
-after 4 days of fertilization (embryonic blastocyst stage) cells are pluripotent where they can develop into any cell in embryo except placenta or amniotic sac cells
127
adult stem cells
occur in small numbers in mature organs & tissue
-multipotent: develop into 2 or more different cell types
-unipotent: develop into one mature cell type
128
regeneration
replacement of dead/damaged cells w same type of cell as before, restoring organ's normal function
129
fibrosis
replacement of damaged tissue w scar tissue composed mainly of collagen produced by fibroblasts
-doesn't restore normal function
130
healing of injury
-bleeding occurs & mast & damaged cells release histamine, increasing blood flow & capillary permeability
-blood clot forms in tissue, knitting edges of cut together & inhibiting spread of pathogens from site of injury; surface of clot forms scab while macrophages underneath begin to clean up tissue debris
-new blood capillaries grow into wound, transforming deeper portions of clot into granulation tissue; macrophages remove blood clot & fibroblasts deposit new collagen in its place
-surface epithelial cells around wound multiply & migrate into wounded area under scab; scab loosens & falls off; epithelium grown thicker
-epithelium undergoes regeneration while CT undergoes fibrosis (scarring)
131
atrophy
shrinkage of tissue through loss in cell size or number
132
senile atrophy
result of normal aging
133
disuse atrophy
results from lack of use
134
necrosis
premature, pathological death of tissue due to trauma, toxins, or infection
135
infarction
sudden tissue death that occurs in cardiac muscle or brain tissue when blood supply is cut off
136
gangrene
tissue necrosis resulting from insufficient blood supply, usually involving infection
-dry: diabetes complication due to arterial & nerve damage (usually in feet)
-decubitus ulcer: form of dry gangrene caused by continual pressure on skin
-wet: occurs in internal organs that become infected
-gas: necrosis of wound resulting from infection w Clostridium species (deadly; may require amputation)
137
apoptosis
programmed cell death
-dissolves webbing between fingers & toes during embryonic development & causes shrinkage of breasts after lactation
138
skin
largest organ of body that consists of outer epidermis & deeper dermis
-hypodermis lies dermis but not true part of skin
139
thick skin
covers palms, soles of feet, & surfaces of fingers & toes
-contains sweat glands
140
thin skin
covers rest of body & contains hair follicles & sebaceous & sweat glands
141
functions of skin
-resistance to trauma & infection
-barrier (absorbing/losing excess water; blocks UV radiation; harmful chemicals- selectively permeable)
-vitamin D synthesis
-sensation
-thermoregulation
-nonverbal communication
142
keratinocytes
synthesize keratin
143
melanocytes
occur only in stratum basale like stem cells & synthesize melanin
-shed melanin-containing fragments from tips of branching processes
-keratinocytes phagocytize these fragments & accumulate melanin on nucleus; melaning shield DNA from UV radiation
144
tactile cells
receptors for sense of touch found in stratum basale
-associated w underlying dermal nerve fiber
145
dendritic cells
immune cells that migrate from bone marrow found in stratum spinosum & granulosum
146
friction ridges
markings on fingertips responsible for fingerprints
147
flexion lines
mark sites where skin folds during flexion of joints
148
freckles
flat melanized patches that vary w heredity & exposure to sun
149
mole/nevus
elevated patch of melanized skin, often w hair
150
birthmarks/hemangiomas
patches of discolored skin caused by benign tumors of blood capillaries
151
nails
hard derivatives of stratum corneum composed of very thin, dead, scaly cells, densely packed together & filled w parallel fibers of hard keratin
152
nail plate
hard part of nail including:
-free edge: overhanging tip of finger/toe
-nail body: visible attached part of nail
-nail root: extends underneath overlying skin
153
nail fold
surrounding skin of nail, separated from margin of nail plate by nail groove
-nail groove & space under free edge collect dirt & bacteria
154
nail bed
skin underlying nail plate
-epidermis=hyponychium
-stratum basale thickens to constitute nail matrix at nail's proximal end
-mitosis accounts for growth of nail
-thickness of nail matrix obscures dermal blood vessels, creating lunule
-eponychium (cuticle- zone of dead skin) overhangs at proximal end of nail
155
hair/pilus
slender filament of keratinized cells that grows from hair follicle
-found almost everywhere on body
156
lanugo hair
fine, downy, unpigmented hair found on fetus in last 3 months of development
157
vellus hair
fine, pale hair that replaces lanugo by time of birth
-body hair of children
-comprises 2/3 of body hair of women & 1/10 of body hair on men
158
terminal hair
longer, coarser, & unpigmented hair that forms eyebrows & eyelashes covers scalp, axillary & pubic hair, male facial hair, & some hair on trunk & limbs
159
hair bulb
swelling at base where hair originates in dermis/hypodermis
-living cells of hair found only here, which grows around dermal papilla (provides nutrition to hair)
160
hair root
remainder of hair within hair follicle
161
hair shaft
portion of hair above skin surface
162
hair matrix
hair's growth center
163
hair medulla
innermost layer; core of loosely arranged cells & air spaces
-prominent in thick hairs
164
hair cortex
external to medulla; constitutes most of hair; several layers of elongated keratinized cells
165
hair cuticle
outermost layer of hair composed of very thin, scaly cell layers that overlap w free edges directed upward
166
hair follicle
diagonal tube that extends into dermis/hypodermis; associated w nerve & muscle fibers
-2 principal layers
-CT root sheath derived from dermis
-epithelial root sheath derived from epidermis
-entwined by hair receptors that respond to hair movements
167
arrector pili
bundles of smooth muscle cells extending from dermal collagen fibers to CT root sheath
-contraction of muscles in response to cold, fear, or stimuli
-cause goosebumps
168
hair color
-eumelanin=brown/black hair
-eumelanin & more pheomelanin=red hair
-some pheomelanin & very little eumelanin=blond hair
-absence of melanin=gray & white hair
169
anagen
active phase of growth
170
catagen
regression period where cell division stop
171
telogen
resting phase where hair is shed
172
alopecia areata
autoimmune disorder where hair follicles attacked
-spots of baldness on scalp & body
173
diffuse hair loss
hair shed from all parts of scalp due to hormones, drugs, iron deficiency
174
male pattern baldness
loss of hair first from only crown region of scalp due to genetic & hormonal factors
175
hirsutism
excessive hairiness
176
apocrine sweat glands
-produce secretions by exocytosis (large lumen)
-ducts lead into nearby hair follicles & not skin surface
-thicker & more milky due to fatty acids
-scent glands that respond to stress & sexual stimulation; don't develop until sexual maturity
177
merocine (eccrine) sweat glands
most numerous glands of skin that produce sweat
-simple tubular gland w twisted coil in dermis/hypodermis
-lined by stratified cuboidal epithelium in dermis & keratinocytes in epidermis
178
sebaceous glands
produce sebum; flask-shaped w short ducts that usually open into hair follicle
-holocrine glands
-sebum keeps skin & hair from becoming dry, brittle, & cracked
179
ceruminous glands
found only in external ear canal where secretion combines w sebum & dead epidermal cells to form earwax (cerumen)
180
mammary glands
milk-producing glands that develop within female breast only during pregnancy & lactation
-modified aprocrine sweat glands that channel rich secretion through ducts to nipple
