Histology Flashcards
What are the 4 main components of the urinary tract?
- 2 kidneys
- ureters
- Bladder
- urethra
What does a nephron comprise of?
Glomerulis PCT Thick limb of the loop of henle Thin limb of the loop of henle DCT Collecting duct
3 layers of the kidney at low microscopic levels?
- Cortex
- Medulla
- Central renal pelvis
What are primarily found in the renal cortex and which appears most prevalent?
Glomerulus
PCT
DCT
PCT appears most prevalent as it is the largest. However, they are all present in equal numbers.
What is a medullary ray?
Specialised areas- collections of loops of henle and collecting diets that originate from nephrons that have their renal corpuscles in the outer part of the cortex.
What does the renal medulla comprise of?
Loop of henle and collecting ducts?
What do the tubular structures in the renal medulla comprise of?
Loop of henle and associated blood vessel
What is a key feature of the capillaries in the glomerulus?
They are fenestrated
What specialised cells are found on the outside of the glomerular basement membrane?
Podocytes
What specialised connective tissue cells support the glomerulus?
Mesangial cells
What is the glomerulus encased in?
Bowman’s capsule
How can capillary endothelial cells and mesangial cells within the glomerulus be distinguished on a microscope slide?
Capillary endothelial cells have a nucleus that lies in the inside of the capillary
Mesangial cells lie between capillaries
Role of mesangial cells In the glomerulus?
-provides structural support for the capillaries in their production of extracellular matrix proteins.
-contraction of the smooth muscle that mesangial cells comprise, tightens the capillaries and so reduces glomerular filtration production rate.
This is impotent in tubuloglomerular feedback
-Also involved in the phagocytosis of glomerular basement membrane break down products
What is tubuloglomerular feedback?
Chemical changes in the tubules act to alter glomerular filtration rate
What are the 3 layers of the glomerular basement membrane?
Glomerular capillary wall
Basement membrane
Foot processes of the podocytes
In the capillary basement membrane of the glomerulus, what prevents the passage of albumin
Fenestrated vascular endothelial cells
How many grams of albumin per day in the urine would highlight a fault in the glomerulus?
3g
What does the glomerular basement membrane contain?
Collagen and negatively charged heparin sulfate molecules
What 3 cells are found in the juxtaglomerular apparatus?
Granular cells
Mecula densa cells
Lacis cells
What are the two components of the juxtaglomerular apparatus?
Afferent arteriole
Macula densa
What does the afferent arteriole contribute to the juxtaglomerular apparatus?
Granular cells
What do granular cells secrete
Renin in response to low BP
What do the macula densa cells in the juxtaglomerular apparatus do in response slow filtration
-slow filtration means more NaCl absorption. The macula densa cells send a signal to reduce afferent arteriole resistance and increase filtration rate
What epithelium is the PCT lined with?
Simple cuboidal epithelium
Why does the PCT require lots of mitochondria?
They actively transport 2/3rd sodium and potassium. Small protein molecules, polypeptides, AA and glucose from the glomerular filtrate in selective reabsorption.
What kind of epithelium do the tick and thin segments of the loop of Henle have?
Thick- low cuboidal
Thin- simple squamous
How can the DCT and PCT be distinguished?
The PCT has a prominent brush border as it contains microvilli, the DCT does not have microvilli
Role of DCT and the epithelium it is lined with a?
Regulates the acid base balance
Low cuboidal epithelium
How can the collecting duct be distinguished?
More plump epithelium than the loop of henle
Round central nucleus
Cuboidal epithelium
2 types of cell in the epithelium of the collecting duct?
Principal cells: responds to aldersterone and ADH
Intercalated cells
-Alpha intercalated cells secrete H+
-Beta intercalated cells secrete bicarbonate
Explain the kidneys blood supply prior to the glomerulus
- Renal branch of the abdominal aorta at the level L1
- Anterior and posterior branches
- interlobar arteries
- arcuate arteries
- interlobular arteries
- afferent arteriole
Explain the blood supply In a nephron following the glomerulus
- Efferent arteriole
- Peritubular capillaries
- Vasa recta
- Renal veins
- IVC
What lines the renal pelvis
Urothelium
-collecting ducts in the medulla drain into the renal pelvis
Role of the renal pelvis?
Transmit urine from the nephron ureter
What does urothelium consist of?
Multilayered stratified epithelium
Role of the ureta and what lines it?
Convert urine by PERISTALIS from the kidney to the bladder
Lined with urothelium
Structure of the ureter
- spiral muscular tubes
- Inner longitudinal layer and outer circular layer
- NO serosa
- Lined by loose fibrous Adventitia
What lines the female urethra?
Urothelium proximally
None karatonising stratified squamous epithelium dismally
What glands open up into the female urethra?
- periurethral
- paraurethral
What are the 3 parts of the male urethra?
- Prostatic (urothelium)
- Membranous (urothelium)
- Penile: proximally pseudostratified
distally: non-karontinising stratified squamous
What part of the kidney is particularly responsive to aldersterone?
Collecting ducts
At what point in the bladder is the muscular is propria most easily discerned?
At the bladder neck
What is the largest organ in the body?
Skin
What is the function of the skin?
- Barrier to infection
- Waterproofing: prevents absorption/desiccation
- Thermoregulation
- Protects against trauma and abrasive forces
- Protection against UV light
- Site of vitamin D synthesis
- Sensation
What are the layers of the skin?
- Epidermis
- Dermis
- Subcutis
What is the outermost layer of the skin called and what is it’s basement membrane made from?
- Epidermis
- Collagen type IV
What are the layers of the epidermis (inside out)?
- Stratum basale
- Stratum spinosum
- Strarum granulosum
- Stratum lucidum
- Stratum corneum
What cells are found in the stratum basale layer?
- Melanocytes
- Basale epithelia cells
- Keratinocytes
What is the role of melanocytes?
- Producing melanin
- They produces melanin in organelles called melanosomes, these are then passed to keratinocytes
What stimulates melanin production?
MSH and ATCH hormones
Role of melanin?
Absorption of both UVA and UVB light for protection from non-ionising radiation
What does skin colour depend on?
Amount and type and melanin.
The number of melanocytes is the same between races
What cells are present in the stratum spinosum?
- Plump polygonal keratinocytes (these are bound together by desmosomes and appear as prominent intercellular adhesions, seen as spikes)
- Langerhan cells: antigen recognition
- Merkel cells: sensory cells
What are the cells in the stratum granulosum?
- Layer of flattened squames
- Haematoxophilic kerato-hyaline granules
- Keratinocytes: a they mature, their cytoplasm fills with kerato-hyaline granules and they die.
In which layer is keratin produced?
Stratum granulosum
Why is the stratum corneum an acellular layer?
It consists of plates of keratin in the form of dead keratinocytes from the stratum granulosum
What is the extra layer of epidermis seen most easily on the palms and soles?
Stratum lucidum
What does the adnexae include?
- Apocrine sweat glands
- Eccrine sweat glands
- Sebaceous glands
What is holocrine secretion and what glands carry it out?
- Sebaceous glands
- Secretion of whole cell contents
Where are apocrine glands found and what is apocrine secretion?
- Around the genitals, anus, armpits and groin
- Secretions comprise elements of the cytoplasm that bud off from the luminal surface
What is the adaptation of the dermo-epidermal junction will helps to anchor the epidermis to the dermis?
-It is ridged. The epidermis protrudes downwards in the dermis forming rete pegs
What are the two elements of the dermis?
- Papillary dermis (lies between the rete pegs)
- Reticular dermis
What are the two mechanoreceptors that can be found in the dermis and what is their role?
Meisnner’s corpuscles: fine touch
Pacinian corpuscles: pressure receptors (produces feelings of vibration and tickle)
What does the subcutis comprise of and what is it’s role?
- White adipose connective tissue and fibrovascular septa
- Role: insulation, shock absorber, store of energy
What does breast tissue comprise of?
Males: just a myoepithelial system of ducts
Females: myoepithelial system of ducts and lobules
These are set in fibroadipose connective tissue
What is the functional component on the breast?
Terminal duct lobular units
What are the two layers the ducts and lobules of the breast?
- Outermyoepithelial contractile cells
- Inner columnar epithelial which can adapt to produce milk?
What happens to the inner layer of secretory cells in the breast during lactation?
They become vacuolated
What layer of the epidermis contains melanocytes?
Stratum basale
What is melanin synthesised from?
Tyrosine
Main cell in the epidermis containing melanin?
Keratinocytes
What does a hair follicle comprise of?
- Hair bulb-downwards extension of the epidermis into the dermis
- Hair papilla: specialised part of the dermis that is richly innervated and vascular
What are the 3 (outermost-innermost) layers of the testis forming a capsule?
-Tunica vaginalis: made of mesothelial with a parietal and visceral layer
Tunica albuginea: thick collagen fibres with - some fibroblasts, myocytes and nerve fibres
-Tunica vasculosa: loose connective tissue - contains blood vessels and lymphatics
What is the average weight of the testis?
15-19g
What does the testicular parenchyma contain?
-Seminiferous tubules
What cells do the seminiferous tubules contain?
- Germ cells in varying stages of maturation
- Sertoli cells
Give the 3 types of spermatogonia resting against the basement membrane of the seminiferous tubules
- Type A darkly stained - stem cells, divide to form:
- Type A pale stained - differentiate to form:
- Type B cells
Explain the appearance of the nucleus of the Sertoli cells
-Irregularly shapes, folded and prominent
Where are leydig cells found?
-In the interstitium, between seminiferous tubules
What is the rete testis and what is it lined with?
- Anastomosing network of tubules at the hilum of the testis
- Simple squamous of low columnar epithelium
What is the function of the rete testis?
- Acts as a mixing chamber for the contents of the seminiferous tubules
- Possible secretions
- Reabsorption of protein from the luminal contents
What are the efferent ducts lined with?
-Ciliated or non ciliated simple columnar epithelium with interspersed basal (cuboidal) cells giving it a pseudostratified appearance
What lines the epididymis?
-Tall columnar cells with atypical cilia
What surrounds the basement membrane of the epididymis?
-Well defined muscular coat
What is the function of the epididymis?
- Absorption of testicular fluid
- Phagocytosis of degenerate spermatozoa
- Production of secretions rich in glycoproteins, sialic acid, glycerylphosphorycholine (role in sperm maturation)
What lines the vas deferens ?
-pseudostratified columnar epithelium with columnar and basal cells
How many layers of smooth muscle does the vas deferens contain?
3
Where is the prostate?
-Surrounds the neck of the bladder and prostatic urethra
What are the lobes of the prostate?
- Anterior
- Middle
- Posterior
- 2x lateral
What are the clinical divisions of the prostate?
- Peripheral (site of cancer development)
- Central (undergoes enlargement with increasing age)
- Transitional
- Peri-urethral
What capsule covers the prostate?
Ill-defined fibro-connective tissue capsule
What are the ducts of the prostate?
- Large primary
- Small secondary
What are the acini of the prostate?
Sac-like cavity in a gland surrounded by secretory cells
Explain the epithelium of the prostatic acini
- Double layered epithelium
- One next to the basement membrane that comprises flattened basal epithelial cells (continuous layer)
- Above this layer is a layer of secretory cells (columnar) with neuroendocrine cells mixed within
What do secretory cells of the prostatic acini secrete?
- PAS (used to determine prostate cancer and used biologically as an enzyme to liquify ejaculation)
- PAP
What does the stroma of the prostate contain?
- Smooth muscle
- Fibroelastic fibres
- Blood vessels
- Nerves
What is benign prostatic hyperplasia?
-Enlargement of the glands and stroma of the prostate, caused by an increased reproduction rate of cells
What are seminal vesicles and where are they found?
- Paired, highly coiled and tubular structure
- Posterolateral to the bladder
Where does the seminal duct empty info?
-Ejaculatory duct
What lines the seminal vesicle?
-Tall, ciliated columnar epithelium that contains vacuoles and lipofuscin
Explain the 3 components of erectile tissue of the penis
- Left and right corpora cavernosa on the dorsal side
- Corpus spongiosum on the dorsal side
What does erectile tissue comprise?
-Irregular vascular spaces separated by fibroelastic tissue and smooth muscle
Give the attachments of the ovary
To broad ligament by mesovary
To uterus by utero-ovarian ligament
To pelvic wall by suspensory ligament
What are the 3 layers of the ovary?
- mesothelium
- Tunica albuginea
- Ovarian stroma (divided into ovarian cortex and medulla)
What does the ovarian cortex and ovarian medulla consist of?
Cortex: Spindle stromal cells
Ovarian follicles
Some leutinised cells
Medulla: loose fibroelastic tissue with blood vessels, lymphatics and nerves
What happens as a primordial follicle develops into a primary follicle?
- FSH secreted from anterior pituitary stimulates the development
- The oocyte enlarges
- The zona pellucida forms around the oocyte
- Granulosa cells proliferate and change from squamous to cuboidal or columnar
What happens as a primary follicle develops into a secondary follicle?
- Formation of the antrum
- The ovarian stroma differentiates into the theca interna and theca externa
Explain he structure of a Graafian follicle
- Ovum is surrounded by a thick zona pellucida
- Corona radiata (layer of granulosa cells)
- Cumulus oophorous (layer of granulosa cells)
What happens to the granulosa and theca cells when the corpus luteum forms?
- The change of the follicle to the corpus luteum is stimulated by LH
- Leutinisation
- The granulosa and theca cells become polygonal, larger and with an abundant of cytoplasm
What is leutinisation?
-Accumulation of lipid
What happens when the corpus luteum regresses?
- Granulosa cells decrease in size, develop phknotic nuclei and accumulate lipid
- Cells undergo dissolution and are phagocytosed
- There is progressive fibrosis by ingrowth of connective tissue
- End result: corpus albicans
What is the corpus albicans?
-Entirely composed of densely packed collagen with occasional follicles
What are the 2 purposes of the Fallopian tube?
- Fertilisation occurs here
- Transports the ovum to the uterus
What are the 4 segments of the Fallopian tube?
- Intramural
- Isthmus
- Ampulla
- Infundibulum
What are the 2 types of Fallopian epithelial cell?
- Ciliated epithelial cells
- Secretory epithelial cells
Explain the muscularis and serosa of the Fallopian tube?
Muscularis - 2 layers of smooth muscle : inner circular
Outer longitudinal
Serosa: connective tissue covered by mesothelium
What are the 3 layers of the uterus?
- Outer serosa
- Middle muscular myometrium
- Inner epithelial endometrium
Describe the endometrium of the uterus
- Stratum basalis : deep basil layer. Not hormonally responsive, not lost during menstruation.
- Stratum spongiosum : superficial functional layer. Hormonally responsive, appearance changes dependent on the stage of the menstrual cycle.
Explain the appearance of the endometrium during the proliferative phase and what influences this?
-Proliferation of endometrium stimulated by oestrogen characterised by:
Straight proliferating glands with mitotic activity
No luminal secretions
Stromal cells are spindled and compact, and show mitotic activity.
Explain the histological appearance of the endometrium during the secretory phase and what influences it?
-Endometrium influenced by progesterone with 3 phases:
Early: epithelial cells of the endometrial glands contain sub-nuclear glycogen vacuoles
Mid: glycogen vacuoles are present above and below the nucleus. The glands become more rounded and the stroma becomes oedematous.
Late: Elongated and saw toothed glands with intraluminal secretions
The stroma: spiral arterioles
Explain the histological appearance of the endometrium during the menstrual phase
-Comes as a result of progesterone withdrawal
-Characterised by : stromal haemorrhage
granulocytes
stromal and glandular fragmentation
What are the 3 layers of the myometrium of the uterus
- Inner longitudinal
- Middle circular
- Outer longitudinal
What are the two components of the cervix?
- Endocervix
- Ectocervix
What lines the stroma of the endocervix?
-simple columnar Ciliated epithelium
What lines the ectocervix?
Non-keratinised stratified squamous epithelium
What epithelium lines the vagina?
Non-keratinising stratified squamous epithelium
What lines the labia minora and majora?
Majora : keratinising stratified squamous epithelium
Minora : mostly non-keratinising stratified squamous epithelium
What are pilcae of the Fallopian tube?
The mucus is thrown into complex branching folds
What are the 3 primary features of the thyroid
- Follicle : contains thyroglobulin
- Follicular epithelial cells : simple cuboidal, becomes columnar with increased metabolic activity. Produces T3 and T4 cells.
- Parafollicular / C cells : Produce calcitonin for Ca2+ homeostasis
What is in the centre of the thyroid follicle
Thyroglobulin
What epithelium lines thyroid follicular cells
-Simple cuboidal
What hormones do thyroid follicular cells produce
- T3: triidothyronine
- T4: Thyroxine
What do parafollicular cells of the thyroid gland produce
Calcitonin
When does the thyroid gland begin producing thyroxine
18-20 weeks
What protein rich material is at the core of the thyroid follicle
- Colloid
- Contains large amounts of thyroglobulin
Explain the synthesis of T1 and T2 hormones in the thyroid
- Iodine is cotransported with Na+ into the follicular cells (iodine trapping).
- Na+ is pumped back of by
Explain the histology of the uterus during menstrual phase
-There is a stromal haemorrhage due to a lack of withdrawal of progesterone
-There are granulocytes in the stroma
Stromal and glandular fragmentation
Explain the histology of the uterus during the proliferative phase
No luminal secretions
Stromal cells : spindled, compact and show mitotic activity
Tortoise glands
Explain the histology of the uterus during the secretory phase
Early: sub-nuclear vacuoles
Mid: vacuoles above and below nucleus
Intraluminal secretions
Rounded glands
Stromal oedema
Late: spiral arteries in stroma
Elongated, saw-soother glands with increased luminal secretions
