SUGER Histology Flashcards by adam iqbal

KIDNEY

pale cortex / dark medulla / 10-15 meduallary pyramids
cortex contains glomeruli and coils of proximal/distal tubules
medulla contains pyramids with straight parts proximaal/distal tubule, loop of Henle, collecting duct

Blood

5/6 branches renal artery
arcuate arteries at medullary/cortical border (give off vasa recta - deep to medulla)
then interlobular arteries penetrate cortex at regular intervals
affertent to glomerulus
efferent from glomerulus (filtered blood) - thin walled and between tubules
acquire fluid and ions -> drain to arcuate veins -> systemic

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GLOMERULUS

blood to glomerulus for filtration
passes primary filtrate to nephron for selected reabsorption
parallel array of fenestrated capillaries ensheathed by podocytes
between loops = mesangiel cells (matrix forming)
afferent arteriole wall produces renin
next to glomerulus = segment of distal tubule with macula densa

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GLOMERULAR TUFT (PAS)

arise from vascular pole of glomerulus = entrance afferent and exit efferent
in this angle lies a distal loop of nephron with palisade of macula densa
capillary loop surrounded by podocyte
surrounded by urinary space - separates glomerulus from bowman’s capsule
arrow to distal tubule
MACULA DENSA - around blood vessels regulate blood flow, provides framework for glomerulus.

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FILTRATION BARRIER

basement membrane
synthesised and maintaiend by endothelial capillary cells and epithelial cells (podocytes) that ensheath them
endothelial = fenestrated
podocytes stand off membrane with foot processes
creates physical pores
pores guarded by filtration membrane
membrane is charged and resists passage of some molecules
water and solutes may pass to urinary space = primary filtrate

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PROXIMAL TUBULES (PAS)

highly coiled (sometimes with straight projection to medulla)
prominent brush border and complex invaginations @ basolateral membrane dark pink
extensive reabsorption here
Na+ active transport with glucose (cotransporter - GLUT)
take up protein and polypeptide by endocytosis
cells contain lyzosomes which break down proteins before returning to circulation
any small negatively charged protein can enter primary filtrate

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PROXIMAL TUBULES 2 (PAS)

this slide - straight portion of proximal tubule
leads to loop of Henle
if glomeruli present = cortex
some project to medulla

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LOOP OF HENLE (PAS)

mostly @ medulla
thick/straight descending, thin loop, thick ascending
thick descend = similar to proximal tubule
thick ascend = similar to distal tubule
longest thin loop penetrate deepest to medulla when glomerulus = cortico-medulla junction
thin descending portion = low permeability to ions and urea, high permeability to water
thin ascending portion retains water, reabsorption Na+ and Cl-
this produces dilute/hypotonic filtrate but a hypertonic interstitium
vasa recta (straight capillaries) run alongside tubules

this slide - thick and thin limbs and vasa recta

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DISTAL TUBULE (PAS)

from medulla to cortex then to vascular pole of glomerulus
macula densa here monitors sodium levels to influence intitial filtration of glomerulus
paler than proximal
deep invaginations of basal plasma membrane with numerous mitochondria
mitochondria indicative of control acid/base balance and concentration of urine (ATP)
with aldosterone sodium reabsorbed, potassium excreted
bicarbonate ions reabsorbed, hydrogen excreted - acidic urine

@ cortex both proximal and distal tubules present

proximal more tightly coiled therefore appear to be more numerous

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COLLECTING DUCTS (PAS)

pale cuboidal cells
wide lumen
starts at cortex, filtrate to collecting tubules than larger ducts
collecting tubules from many nephrons coalesce to larger ducts and form visible streaks - medullary rays
few organelles
collecting tubules - dark intercalated cells with high mitochondria
surrounded by hypertonic medium interstitial from loop of Henle
ADH increases permeability to water (concentrates urine)

prone to kidney stones and infection

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JUXTAGLOMERULAR APPARATUS (PAS)

afferent/efferent arterioles, macula densa, lacis cells
afferent - cells produce renin - granules in cytoplasm
renin catalyses angiotensin 1 (liver) -> angiotensin 2 (conversion at lungs) -> aldosterone release by suprarenal cortex -> reabsorption of sodium and water @ distal tubules and collecting ducts
lacis cells and macula densa regulate renin secretion by monitoring sodium levels

this slide - obvious macula densa

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UROTHELIUM

ureters, bladder and most urethra
pseudo-stratified epithelium
surface cells adapted to withstand prolonged urine exposure
3-8 layers (distension dependent)
basal cells = cuboidal
above = columnar (relaxed)
surface = large, binucleate umbrella cells

umbrella cells:

thickened membrane plates joined by thin membrane bands
lipid composition (unique)
relaxed plated = perpendicular to membrane
stretched = drawn to surface of cell

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URETER

epithelial tube with 2 helical layers of smooth muscle
star shaped lumen
towards bladder = longitudinal smooth muscle
3 constrictions (kidney stones will lodge here)
1. origin (pelvis of kidney)
2. at sacro-iliac joint (passes to true pelvis)
3. as enters postero-inferior bladder surface
reflux prevented by compression of ureter by muscular wall bladder
contains blood vessels and adipose
smooth muscle for peristaltic contraction

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URINARY BLADDER

wall = thick bundles of smooth muscle with no preferred direction except neck = 3 distinct layers
1. innermost = longitudinal projects inferiorly and turns transversely to form a sphincter around prostatic urethre (male) and external meatus (female)

thrown into folds w/ umbrella cells

walls of bladder contains small nerves (autonomic)

sympathetic NS = mainly blood vessels at bladder

inset = nerves

micturition

when external sphincter relaxes (sympathetic) and muscle wall (detrusor) contracts (para)

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PROSTATIC URETHRA

urethra longer in males

prostatic
membranous
bulbous
pendulous

urothelium (pseudo-stratified columnar) except at distal end
mucus glands along length
distal urethra = stratified squamous (male and female)
both sexes = striated (voluntary) muscle sphincter from muscles of pelvic diaphragm around membranous part
under prostatic urothelium = dense fibrous connective tissue to prevent distension

inset = U-shaped prostatic urethra

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TESTES

within collagenous capsule = tunica albuginea
within fibrous septa to 250 lobules (each lobule with up to 4 germ cell producing semniferous (tubules)
semniferous tubule = 50cm loop (open both ends)
drain to rete testes (channels)
Leydig cells between semniferous tubules

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SEMNIFEROUS TUBULE

stratified epithelium with support (sertoli) and germ line (developing spermatazoa)
at periphery = germinal epithelial
GE produces large cells with speckled chromatin = spermatagonis
spermatogonia develop to spermatocytes
spermatocytes pass blood testis barrier created by Sertoli
Sertoli = blood testis barrier and nurture sperm
production = 64 days
maturation wave passes slowly down each tubule

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SEMNIFEROUS TUBULES

thin fibrous capsule
closest to membrane = germinal epithelium with spermatogonia (speckled)
between cells are smaller primary spermatocytes and Sertoli cells (pale irregular nuclei)
towards centre depends on stage in cycle
sometimes primary/secondary spermatocytes (small dense nuclei)
otherms more mature (narrow and elongated heads)
between tubules = leydig clumps

arrow to spermatid

reduction division (2n-1n -> first meiotic) takes place when primary to secondary @ luminal side of blood testis barrier i.e. not in contact with blood stream

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EPIDIDYMIS

rete testis = cuboidal ep
rete testis to efferent ductules (similar)
epididymis = single 5m coiled tube
thick fibrous capsule attached to mediastinum of testes posteriorly - storage and maturation site for sperm aggregated within lumen
tall pseudo-stratified columnar ep
small rounded basal cells support tall columnar with microvilli (stereocilia)
stereocilia (non-motile) reabsorb seminal fluid, phagocytose damaged sperm and cell debris. also nutrients for sperm
thin layer of smooth muscle thicker as approaches vas

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VAS DEFERENS

spirally arranged smooth muscle
similar to epididymis but shorter cells and microvilli
sometimes has longitudinal folds - lamina propria
sudden and rhythmical contraction expels sperm

thick muscular wall makes vas feel cord like

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SEMINAL VESICLE

highly coiled glands at postero inferior bladder
double layered capsule of smooth muscle
long narrow folds
stimulated by testosterone - enlarge and secrete creamy opalescent fluid with acid pH. rich in globulin, vitamin C, amino acids and sugars
contraction of smoooth muscle mixes with spermatozoa
simple columnar epithelium

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PROSTATE

50 branched tubular glands
smooth muscle matrix
smooth muscle capsule around all
3 layers (concentric) of glands - mucosal - submucosal - main
@ ejaculation, contract and mix secretions @ ejaculatory duct

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PROSTATIC EPITHELIUM

glands varied - straight, coiled, branched
epithelium thrown into broad, branching folds
with testosterone, cells increase in height and secrete digestive enzymes - acid phosphatase (major component of seminal fluid) - (PSA) prostate specific antigen
lumen often with sec product / calcified glycoprotein

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PROSTATE 2

this slide L - skeletal muscle at underside of prostate - pelvic diaphragm with levator ani
this slide R - spiral tubular gland at submucosal level

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PENILE URETHRA

prostatic, membranous, penile
membranous and penile = non-secreting pseudostratified columnar
at distal end = stratified squamous epithelium (within glans)
bulbo-urethral glands within membranous urethra produce watery galactose rich secretion, precedes main ejaculate - can sometimes be a problem with catheterisation

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PENIS

erectile compartments = large endothelium lined blood vessels supported by connective tissue
each surrounded by compact collagen layer = tunica albuginea
helicine branches of pudendal artery
when flaccid arteries transmit very little blood due to artero-venous shunts
para. stimulus shut shunts (point and shoot)
most skin = hairy, loosely attached to columns - except prepuce and glans (non-kerat)

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VAGINA

stratified squamous thinly keratinised at vulval end
thin pre-puberty and post menopause
beneath epithelium = lamina propria with small blood vessels (moisture by diffusion)
surrounding epithelium = fibro muschular tube with collagen/elastic and smooth muscle
sphincter of skeletal muscle at lower end
bartholin glands - mucus posterolaterally at lower end of vagina
with age = weaker fibro-muscular tube

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EPITHELIAL SQUAMES

in menstrual cycle surface cells accumulate glycogen and flake off
desquamated cells rupture and bacteria generate lactic acid
low pH at vagina

pale green cells - outermost layer, predominate at first half of menstrual cycle

pink cells - deeper layer

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CERVIS

protrudes to anterior wall vagina
surrounded by gulley - lateral, anterior, posterior ornices
outer surface - SSNKE (identical to vagina)
cervical canal (between internal and external os) = tall columnar epithelium thrown into deep gland-like folds
stroma = fibrous connective and smooth muscle
this slide - external os

CERVICAL LINING

secretes mucus - consitency of which varies throughout menstrual cycle
first half - thin and watery
second half - viscous after ovulation as plug to prevent microorganism entry
transitional zone - between sensitive cervical lining and other stratified squamous epithelium prone to infection and lesion
this slide - mucus glands visible

UTERINE BODY

3 poorly defined layers myometrium smooth muscle
lined by epithelial endometrium
myometrium hormonally sensitive

hyperplasia and hypertrophy @ pregnancy

large arteries and veins between inner and middle layers, also supply endometrium and give rise to spiral arteries (significant @ menstruation)

ENDOMETRIUM

uterus = simple columnar with tubular glands

PROLIFERATIVE PHASE - first half, stroma tickens and length glands increase

SECRETORY PHASE - second half of menstrual cycle - glands secrete and stroma differentitates to environment for ovum

MENSTRUATION - most endometrium shef leadving only bases of glands - MENSES = 4 days

PROLIFERATIVE ENDOMETRIUM

post menses
10 days, regrow glands stroma and blood vessels
at end of proliferation = ovulation, then secretory
TUBULAR GLANDS APPEAR STRAIGHT and cells do not secrete endometrial mucus
stroma compact
uncoiled arteries and veins
mitotically dividing cells within glands and stroma
simple glands (often circular)
loose connective tissue

SECRETORY ENDOMETRIUM

ovulation @ day 14-16
cells have large vacuole of glycogen below nuclei
from these stores syntehsise mucins
glands = irregular / sacculated with secretions @ lumen
stroma oedematous
arteries lengthen and become spiral
@ end (late phase) spiral arteries close down and blood leaks to stroma = anoxia therfoer decidua detaches and menses begins

UTERINE TUBES

10 cm within broad ligament
4 regions:
1. intramural
2. short narrow isthmus
3. long ampulla
4. wide infundibulum (with fimbria)
lumen varies in appearance
UTERINE = star-shaped
INFUNDIBULUM = complex folds and wide
ciliated - cilia become longer and beat more strongly soon after ovulation

UTERINE TUBE EPITHELIUM

two helical layers of smooth muscle (inner circular) and outer (longitudinal)
simple columnar epithelium - ciliated and mucous secreting
epithelium is hormonally-sensitive - cels taller and cilia beat more strongly around ovulation
also secretions are thinner and more copioius at this time

fertilised at ampulla
ectopic pregnancy at uterine tube
surrounded by broad ligament and mesovarium connecting ovary and broad ligament

OVARY

surface = germinal epithelium (thick BM)
attached by mesovarium mesentery to upper posterior surface of broad ligament (continuous with ovary)
3 parts
1. hilum - blood vessels, lymphatics and nerves leave here
2. medulla - stromal cells with testosterone secreting cells (similar to Leydig)
3. cortex - primordial germ cells and follicles from primary, secondary, atritic

GERM CELL PRODUCTION - to ovary @ w10 of devlopment - immediately start meiosis and reach prophase 1 of meiosis (primary oocutes @ birth)

reawakened with each menstrual cycle - up to 20 cells begin to differentiate but only 1 acheives maturation -remainder resorbed

FOLLICULAR DEVELOPMENT

@ cortex, many germ cells many = dormant primordial follicles with germ cell in theca from stromal cells
theca - simple squamous (primordial), later to cuboidal or columnar
then differentiates into granulosa cells = theca interna that begin to secrete oestrogen and theca externa (flattened) and follicle becomes secondary
further growth and development -> mature Graafian follicle with fluid-filled antrum
follices perish as atritic
once oocyte released from Graafian follicle theca persists and releases oestrogen and progesterone as corpus luteum

this slide - primordial follicles

FOLLICULAR DEVELOPMENT 2

TL - secondary follicle
TR - primary follicle
BL - mature graafian follicle
BR - primordial follicle

CORPUS LUTEUM

when Graafian follicle ruptures - antrum collapses = central blood clot
remaining thecal cells persist as corpus luteum
with lutinising hormone cells continue to secrete oestrogen and progesterone for 10 days - support secretory endometrium
if fertilisation occurs, corpus luteum persists for 4 weeks till placenta
most thecal cells produce progesterone but some at centre synthesise oestrogen - thecal lutein cells
final involution forms pale fibrous mass - corpus albican

this slide - theca interna and blood vessels

CORPUS LUTEUM 2

centre contains pale staining amorphous material and blood clot
surround is wide band of cells from theca interna invaded by blood vessels
theca externa also contains many blood vessels

theca externa - stellate shape, small, pale

theca interna - large, globular, intense pink

PITUITARY GLAND

anterior / posterior

POSTERIOR - neuronal origin, down growth of brain, pituitary stalk to median eminence of mid-brain @ floor of V3

supra optic and para-ventricular nuclei

oxytocin
vasopressin

ANTERIOR (TROPHIC) - epithelial origin. roof of primitive gut. adheres @ anterior border of posterior pituitary and surrounds stalk (pars tuberalis)

growth hormone
thyroid stimulating hormone
follicle stimulating hormone

PITUITARY PORTAL SYSTEM @ ANTERIOR

release trophic @ anterior pituitary regulated by factors @ neurons of hypothalamus
project to medial eminence
here they release secretions which are taken up by capillaries of pituitary portal and carried to anterior lobe
then act on hormone secreting cells

“portal system” = one that starts and ends @ capillaries

ANTERIOR PITUITARY

3 cell types
1. stain heavily with acid dyes - alpha cells / acidophils /eosinophilic (dark red) growth hormone
2. stain heavily with basic dyes - beta cells / basophils (dark blue) thyrotrophs/gonadotrophs/cotricotrophs
3. stain weakly chromophobes, undifferentiated and no hormone
cells with no stain may be immature of any type

anterior pituitary is darker staining than posterior

ANTERIOR PITUITARY 2

peptide based hormones in GRANULES
acidophils/basophils = small dark hormone containing granules
chromophobes = few or none

POSTERIOR PITUITARY

PALE STAIN H&E
axonal tracts and nerve endings of cell bodies @ hypothalamus (supraoptic or paraventricular nuclei) @ walls of V3
swollen nerve terminals (Herring bodies) contain dark neuro-secreting granules - brown
granules contain:
1) OXYTOCIN; 2) VASOPRESSIN
hormones bound to carrier protein that is also secreted
much tissue (blue staining) is nerve axon/connective tissue

OXYTOCIN - contraction of uterus, dilation of birth canal, contraction of myoepithelial cells around milk ducts + erect nipple for lactation

PINEAL GLAND

small gland
backward projection of V3 between corpus callosum
covered by meninges
calcium may accumulate making it visible on brain X-Ray
irregular clumps of neurone-like pinealocytes linked by glial cells
innervation = autonomic
secretes melatonin - diurnal rhythms
UNIFORM

this slide - loose layers of meninges @ bottom, small blood vessels @ pia

THYROID FOLLICLES

lies between neck of thyroid cartilage and 4th tracheal ring
midling thyroglossal ligamnet links gland to foramen caecum of tongue
THYROXINE AND CALCITONIN
thyroxine producing cells arranged in follicles (hollow spheres)
simple cuboidal epithelium
centre of each follicle filled with colloid rich thyroglobulin
height of cells varies with metabolic activity
flattened when dormant
emptying when active/ if full when dormant
thyroid gland contains lymphocytes
parathyroid gland is posterior

FOLLICULAR PHASES

cyclical
synthesise thyroglobulin and store within follicle
after dormant period re-sorb and break down colloid and release active hormone (T4) into bloodstream

C CELLS

calcitonin producing cells
clumps between follicles
parafollicular
sometimes between BM and follicular cells

calcitonin is antagonistic to parathormone

calcitonin @ high blood calcium levels

lowers serum calcium by promoting uptake of calcium in blood to bones (and muscles)

inhibits absorption of calcium from blood

PARATHYROID

4 @ dorsal surface of thyroid
mixture of fat cells and other secretory cells in clusters or short cords
CHIEF CELL - small an palely stained - very small granules = parathormone (calcium from bone to serum)
larger pink staining OXYPHIL cells fewer in number

PANCREATIC ISLETS

5% of pancreatic mass, 4 types:
1. BETA - INSULIN - 70%
2. ALPHA - GLUCAGON - 20%
3. DELTA - SOMATOTSTATIN - 8%
4. PANCREATIC POLYPEPTIDE SECRETING CELLS - 2%

beta cells at periphery of islets form cords to centre. other cell types lie between cords, plexus of capillaries/veins transport hormones to hepatic portal system

ADRENAL GLANDS

OUTER CORTEX = STEROID HORMONES
INNER MEDULLA = ADRENALINE AND NORADRENALINE
centripetal blood supply
arterioles from capsular arteries to cortical sinusoids and direct links to medulla
both systems drain to central vein -> to renal vein or direct to IVC

ADRENAL CORTEX

3 zones
1. OUTER GLOMERULAR (narrow) - ALDOSTERONE AND MINERALOCORTICOIDS
2. INTERMEDIATE THICK FASCICULAR long parallel cords responsible for CORTISOL and GLUCOCORTICOIDS
3. INNER RETICULAR ZONE anastomosing cords of cells that produce testosterone and other androgenics (DARKER STAINING)

do not store the steroid hormones they synthesise - discharged to sinusoids

accumulate droplets of fat and cholesterol from which hormones are synthesised = pale-staining of many cells

ADRENAL MEDULLA

irregular clumps interspersed with blood vessels
2 types of secretory cells

ADRENALINE
NORADRENALINE

stored in small neurosecretory granules in cytoplasm of cell until required

bathed in blood draining from adrenal cortex, thus influenced by steroid hormones

sympathetic stimulation

TESTICLE

ovaries/testes/placenta are also hormone secreting

this slide - Leydig cells clumped between semniferous tubules

EPIDERMIS

4 layers

GERMINATIVE - single layer
SPINOUS - thickest
GRANULAR - narrow with keratohyaline
DEAD LAYER - dead keratinised squames, thickness varies depending on location and abrasion

DERMIS:

2 layers

rich in collagen (close to epidermis)
deeper fatty layers

KERATINISED EPITHELIUM

thickest @ soles of feet and on hands (hairless) - subject to compression
thin on parts of abdomen/thorax and lips
epidermis compact and boundary with dermis wavy creating dermal piapillae
at upper boundary = thin, darkly-staining granular layer, synthesises keratin that surrounds dead squames - prominent keratohyaline

GERMINAL EPITHELIUM AND MELANOCYTES

majority = keratinocytes (from stem cells at germinal layer)
also within germinal layer = melanocytes, from neural crest of embryo
produce melanin - transferred to keratinocytes of basal and prickle cell layers
amount of melanin proportional to skin colour

SPINOUS (PRICKLE) CELL LAYER

thickest layer - joined by desmosomes - prevent skin splitting when stretched
if shrink - desmosomes become obvious and cells appear spiny
within = LANGERHAN’S CELLS = pale cytoplasm and irregularly shaped nucleus
@ basal layer of epidermis = MERKEL CELLS - difficult to resolve, synapse with nerve fibres @ dermis and transmit fine touch

HAIRY SKIN

roots of hair project from dermis, but are of epidermal origin
arise from geminative epithelium within hair bulb that contains melanocytes - hair colour
hair lengthens when a root sheath of epidermis with same layers as rest of skin but thicker BM = glassy membrane
surrounded by collagenous follicle sheath with erector pili (smooth muscle) (& autonomic nerve)
sympathetic stimulation = stand on end
to shaft = sebaceous glands (lubrication)
some parts of body with hairless sebaceous glands - face and groin

FINGERNAILS

compacted keratin
arise from nail matrix cell under a fold of skin (eopnychium/cuticle) at proximal end of nail
nail lengthens across epidermal nail bed, remains firmly attached at distal end where underlain by a skin fold - hyponychium

SWEAT GLANDS

dermis = 2 layers - outer with collagen and elastic fibres (fibrous layer) deeper = adipose (fatty tissue)
@ dermis = roots of hairs, glands, plexi of blood vessels, sensory transducers and nerve endings
most common = ECCRINE SWEAT GLANDS - lined by glycogen rich cells
tighly coiled knot of fluid secreting cells and straight duct with simple cuboidal epithelium
duct to surface of skin
coiled section surrounded by MYOEPITHELIAL CELLS
@ armpits and anus = apocrine sweat glands - earwax

SENSORY NERVE ENDINGS (OSMIUM TETROXIDE)

many are too fine to be resolved except:
1. PACINIAN CORPUSCLE - pressure @ dermis/pancreas - large structure with nerve ending at core - resembles an onion
2. MEISSNER’S CORPUSCLE - numerous with spiral appearance @ dermal papillae

EYELID

outside = thin hairy skin with row of prominent lashes
sweat glands discharge to outer surface of eyelid
inside = conjunctiva = stratified columnar with 2 cell layers
@ substance = single row of hairs, striated muscle (orbicularis oris) and glands to keep inside surface moist
largest gland = MEIBOMIAN GLAND modified sweat = lipid rich secretion - reduces evaporation
smaller sweat and sebaceous
this slide - meibomian gland

BREAST

start as mainly adipose tissue, into which grow solid cords from the nipple
branch out/hollow to form lactiferous ducts but no milk producing alveolar cells
15-20 segments formed by fibrous strands from nipple
suspensory ligaments of Cooper
ducts open to nipple via lactiferous sinuses
blind ended before pregnancy
adult inactive breasts are responsive to fluctuating hormones
@ 2nd half of each mesntrual cycle PROGESTERON PROMOTED OEDEMA - distension of segments

NIPPLE

area of skin with raised fibro-muscular core
12-20 small openings of lactiferous ducts
surrounded by areola with raised sebaceous glands = MONTGOMERY’S TUBERCLES
undergo pigmentation at pregnancy

lacteriferous duct = stratified cuboidal epithelium - if nucleus roughly circular = cuboidal

contains muscle which many change protuberance of nipple

LACTATING BREAST

@ first trimester, enter proliferative phase stimulated by OESTROGEN, GROWTH HORMONE + CORTISOL
ducts divide and secretory alveoli develop at ends - columnar surrounded by flattened myoepithelial cells
alveolar cells mature and secretory material builds up within them and lumena, at the same time the stroma becomes depleted of adipose tissue
@ latter stages = lymphocytes

lactation suppressed by high levels of oestrogen and progesterone

BREAST TISSUE - LACTATING

alveoli displace much of fat
contain secretory cells that produce milk proteins and fats and ion rich watery solution
milk protein and fat synthesis by same cells within alveoli but discharged differently
milk fats - apocrine secretion
milk protein - merocrine process

this slide = fibrous connective tissue - stroma

LACTIFEROUS DUCT

gynecomastia = proliferation of lactiferous ducts

lobar carcinomas = dysplasia in small ducts

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