SUGER: Histology Flashcards
What is a medullary ray in the renal cortex?
A collection of loops of Henle and collecting ducts. The corpuscles (glomerulus and Bowman’s capsule) of these nephrons are in the outer cortex.
Are there any glomeruli in the renal medulla?
No
What is the glomerulus?
Tuft of convoluted fenestrated capillaries
The capillary endothelial cells of the glomerulus rest on a basement membrane. What lines the glomerular basement membrane on the other side?
Podocytes
What encases the glomerulus?
Bowman’s capsule
In the glomerulus there are mainly two types of cells; capillary endothelial cells and mesangial cells. How can you tell the difference between these two cells histologically?
The capillary endothelial cell nucleus lies on the inside of capillaries.
Mesangial cells lie between capillaries.
What is the function of mesangial cells in the glomerulus?
Mesangial cells can control glomerular filtration rate by contracting the capillaries. They are specialised connective tissue cells which are contractile and behave like smooth muscle.
How is the glomerular basement membrane specialised for filtration?
It is a double layer made of two basement membranes.
Contains collagen and negatively charged heparin sulphate molecules.
List the layers of the glomerular basement membrane from the capillary endothelial cells to the podocyte foot processes.
Lamina lucida interna
Lamina densa (2 layers)
Lamina lucida externa
What is the function of the podocyte slit membrane/diaphragm in the glomerulus?
Podocyte foot processes act as an additional barrier for filtration, the slit membrane (composed of proteins e.g. nephrin) allows smaller molecules through for filtration, while keeping larger molecules e.g. albumin in the capillaries.
What are the two main components of the juxtaglomerular apparatus?
Vascular component (afferent and efferent arterioles)
Tubular component (macula densa, specialised region of the distal convoluted tubule)
The endothelium of the afferent arterioles in the juxtaglomerular apparatus are expanded to form a mass of granular cells. What are the two key functions of these cells?
Detect changes in blood pressure.
Secrete renin.
Briefly explain how glomerulotubular feedback occurs.
If glomerular filtration is slow, more sodium is absorbed, which is detected by macula densa cells, which send a signal to reduce afferent arteriole resistance, which increases speed of glomerular filtration.
What are four histologically identifying features of the proximal convoluted tubule?
Simple cuboidal epithelium.
Central round nuclei
Prominent brush border on the luminal surface (due to microvillous processes)
Cytoplasm is eosinophilic because the cells are rich in mitochondria
Why do the epithelial cells of the proximal convoluted tubule need lots of mitochondria?
Actively transport ions (sodium, potassium) from the glomerular filtrate
Is the descending loop of Henle thick or thin? Describe the epithelium.
Thin. Simple squamous epithelium.
Is the ascending loop of Henle thick or thin? Describe the epithelium.
Initially thin like descending loop, then thick. Simple low cuboidal epithelium.
What is the vasa recta in the nephron?
Dense network of blood vessels that supplies the loop of Henle.
How is the distal convoluted tubule different to the proximal convoluted tubule histologically?
Distal convoluted tubule does not have microvilli (no prominent brush border).
How can collecting ducts be distinguished from the loop of Henle in renal medulla samples?
‘Plumper’ epithelium.
Round central nuclei.
Where in the nephron would you find aquaporin II?
Collecting duct epithelium
What type of epithelium lines the renal pelvis and ureters?
Urothelium - a multilayered stratified epithelium
Describe urothelium. How is urothelium specially adapted to line the renal pelvis and ureters?
Specialised layer of umbrella cells with tight cellular junctions; prevents urine from leaving renal pelvis (urine proof).
Underneath umbrella cells; pseudostratified layer of polygonal cells and basal layer of cuboidal cells.
What epithelium type lines the urethra?
Proximally: urothelium
Distally: non-keratinising stratified squamous epithelium
Which structure appears the most prevalent in the renal cortex? Why?
Proximal convoluted tubule.
Because it is convoluted, so one will appear multiple times in a section, and it is longer than distal convoluted tubule.
What type of epithelium lines the renal pelvis?
Urothelium
Does the ureter have a muscularis mucosa?
No
How many layers of muscularis propria does the bladder have?
3 layers (same as stomach)
Which part of the urethra is surrounded by the external sphincter?
Membranous urethra
Is the external sphincter of the urethra composed of smooth or skeletal muscle?
Skeletal muscle
What three layers form the capsule of the testis, listing them from outermost to innermost?
Tunica vaginalis
Tunica albuginea
Tunica vasculosa
Which layer of the capsule of the testis is a projection of the peritoneum, and therefore has a parietal and visceral layer, and is composed of a flattened layer of mesothelial cells?
Tunica vaginalis (outermost layer)
Which layer of the capsule of the testis is composed of collagen fibres with some fibroblasts, myocytes, and nerve fibres?
Tunica albuginea (middle layer)
Which layer of the capsule of the testis is composed of loose connective tissue containing blood vessels and lymphatics?
Tunica vasculosa (innermost layer)
Where do spermatozoa form in the testis?
Seminiferous tubules
Spermatozoa are formed in the seminiferous tubules. Describe the path of spermatozoa from these tubules to ejaculation (7 steps).
-> straight tubules
-> rete testis
-> efferent ducts
-> epididymis
-> vas deferens (leaving testis)
-> ejaculatory duct (receiving secretions from seminal vesicle)
-> urethra (receiving secretions from prostate)
What is the testicular parenchyma divided into?
Lobules (around 250), each formed of 1-4 seminiferous tubules.
What divides the testicular parenchymal lobules?
Fibrous septa (originating from the capsule)
What cells rest on the seminiferous tubule basement membrane in the testis?
Spermatogonia and sertoli cells.
What are the three types of spermatogonia?
Type Ad (darkly stained - stem cell population)
Type Ap (pale stained - develop into Type B)
Type B
What are the names of the 5 stages of spermatogenesis, from stem cell to mature, fully differentiated sperm cells?
Spermatogonia (stem cells)
Primary spermatocyte
Secondary spermatocyte
Spermatid
Spermatozoa (mature sperm cells)
How are sertoli cells in the seminiferous tubules identifiable histologically?
Irregularly shaped and folded nuclei with prominent nucleolus.
Sertoli cells are columnar cells found on the basement membrane of the seminiferous tubules in the testis. What is the purpose of sertoli cells?
To support, protect, and provide nutrients to the stem cells (spermatogonia) by sending out cytoplasmic projections around them.
Spermatogenic cells are in constant contact with Sertoli cells.
Also play a role in paracrine and endocrine control of spermatogenesis.
What two structures form the head of spermatozoa?
Acrosomal cap (containing enzymes)
Nucleus
What would you find in the midpiece of the spermatozoa?
Spiral mitochondria wrapped around an axoneme (specialised cilium responsible for sperm motility)
What is the tail of spermatozoa principally composed of?
The axoneme (specialised cilium responsible for sperm motility) surrounded by a plasma membrane.
Leydig cells are found singly and in clusters in the interstitium between seminiferous tubules of the testis. What is the key function of leydig cells?
Produce testosterone.
The rete testis are an anastomising network of tubules at the hilum of the testis. What is the key purpose of the rete testis?
Act as a mixing chamber for contents of the seminiferous tubules.
(unknown if secretory role, might also reabsorb proteins)
What sort of epithelium lines the rete testis?
Simple squamous or low columnar epithelium on a thick basement membrane.
The epididymis contains a highly convoluted epididymal duct (5m long!). What sort of epithelium lines the epididymis?
Tall columnar cells with long atypical cilia (non-motile).
Thick basement membrane with a well defined muscular coat.
What sort of epithelium lines the 12-15 efferent ducts, which empty into the epididymis?
Ciliated and non-ciliated simple columnar epithelium, with interspersed cuboidal cells - this gives a pseudo-stratified appearance.
What happens to defective spermatozoa in the epididymis?
Phagocytosis
What sort of epithelium lines the vas deferens?
Pseudo-stratified columnar epithelium, with some basal cells.
How many layers does the thick muscular wall of the vas deferens have?
3 layers
What surrounds the prostate?
Fibro-connective tissue capsule
What proenzyme do columnar secretory cells in the glandular acini of the prostate produce that helps make semen less viscous, by breaking down heavy proteins into smaller polypeptides?
Prostate Specific Antigen (PSA)
Which part of the prostate, containing mainly smooth muscle cells, often enlarges with age?
Stroma
The seminal vesicles are highly coiled tubular structures that empty into the ejaculatory duct. What sort of epithelium lines the seminal vesicles?
Tall non-ciliated columnar epithelium.
What part of the male reproductive system produces 70-80% of ejaculate?
Seminal vesicles (secretion contains nutrients for spermatozoa)
What is erectile tissue composed of histologically?
Irregular vascular spaces, separated by fibroelastic tissue and smooth muscle.
What are the three components of erectile tissue?
Left and right corpora cavernosa (dorsal side)
Corpus spongiosum (inferior side, surrounds urethra)
What are the corpora cavernosa and corpus spongiosum each surrounded by, and how does this cause the penis to become erect?
Dense fibrous connective tissue
When vascular spaces of erectile tissue engorge, the pressure rises, causing penis to become erect.
What attaches the ovary to the broad ligament?
The mesovarium (a short mesentery)
The ovary is covered by peritoneum. What does this mean is seen as the outer layer of the ovary histologically?
A single layer of modified mesothelium.
What are the three layers of ovarian tissue?
Peritoneum
Tunic albuginea
Stroma (divided into cortex and medulla)
What three identifying characteristics of the ovarian cortex can be seen histologically?
Spindle stromal cells (arranged in whorls/storiform pattern)
Ovarian follicles
Some leutinised cells
What two different tissues make up the ovarian medulla?
Loose fibroelastic tissue with blood vessels, lymphatics, and nerves.
Rete ovarii (the female version of the rete testis) at the hilum of the ovary.
The first stage of follicle development are primordial follicles. Where are primordial follicles found?
At the periphery of the ovarian cortex.
What is a primordial follicle composed of?
Primary oocyte in resting state, surrounded by single layer of squamous epithelial (granulosa) cells.
How many primordial follicles develop into primary follicles during each menstrual cycle?
30-40
What hormone secreted by the anterior pituitary causes primordial follicles to start developing into primary follicles?
Cyclic FSH (follicle-stimulating hormone)
What changes does FSH trigger in primordial follicles to cause them to develop into primary follicles?
Enlargement of oocyte.
Granulosa cells enlarge to change from squamous epithelium into cuboidal/columnar epithelium.
Zona pellucida forms directly around oocyte, between oocyte and epithelium.
FSH causes primordial follicles to develop into primary follicles, and then into secondary follicles. What changes occur between primary and secondary follicles?
Granulosa cells proliferate.
Spaces form between granulosa cells containing follicular fluid (eventually these join to become the follicular antrum)
Stroma forms two distinct layers around granulosa cells (theca interna and theca externa).
What cells in the follicle secrete oestrogen?
Theca interna cells of the stroma.
Of the 30-40 follicles that begin developing from primordial follicles during each menstrual cycle, how many then mature and ovulate into ovarian tube?
Only a few become mature (Graafian) follicles, and usually only one ovum with ovulate.
In the mature (graafian) follicle, what is the ovum surrounded by?
Thick zona pellucida surrounded by corona radiata (made of granulosa cells), then atram (filled with follicular fluid), more granulosa cells, then theca interna, theca externa.
What surrounds the antram (space filled with follicular fluid) of the mature follicle?
Granulosa cells
At ovulation, the follicle ruptures onto the surface of the ovary. What hormone triggers this to occur?
LH (leutinising hormone)
What is leutinisation?
Accumulation of lipid in the granulosa cells and theca cells, forming the corpus luteum.
What happens to the corpus luteum if pregnancy does not occur with 8-9 days of ovulation?
Regression; cells are eventually phagocytosed.
(Corpus luteum is eventually replaced by fibrous connective tissue made by stromal cells, forming corpus albicans)
What are the four segments of the uterine tube?
Infundibulum (trumpet shaped opening to peritoneum)
Ampulla (expanded area)
Isthmus (thick walled portion)
Intramural (inside uterine wall)
Is the inside of the ovarian tube smooth or folded?
Folded into plicae
What are the two main types of epithelial cells of the ovarian tube?
Secretory and ciliated.
What type of epithelial cells are most prevalent at the infundibulum end of the ovarian tube?
Ciliated
What type of epithelial cells are most prevalent at the uterine end of the ovarian tube?
Secretory
What are the two layers of the ovarian tube muscularis (myosalpinx)?
Inner circular layer
Outer longitudinal layer
Describe the outer layer of the ovarian tube histologically.
Loose fibrous connective tissue covered by mesothelium.
What are the three layers of the body of the uterus?
Serosa
Myometrium
Endometrium
What are the two layers of the endometrium?
Deep permanent layer (stratum basalis)
Superficial functional layer (stratum spongiosum)
The superficial functional layer/stratum spongiosum of the endometrium is responsive to hormones and changes during the menstrual cycle.
Oestrogen stimulates the proliferative phase. What changes occur to the endometrium in this phase that can be seen histologically?
Straight proliferating glands with mitotic activity.
Stromal cells are spindled, compact, with mitotic activity.
The superficial functional layer/stratum spongiosum of the endometrium is responsive to hormones and changes during the menstrual cycle.
Progesterone stimulates the secretory phase. What changes occur to the endometrium in this phase that can be seen histologically?
Early secretory phase = sub-nuclear glycogen vacuoles.
Mid secretory phase = vacuoles above and below nucleus, glands more rounded, stroma-oedema. Secretions visible in glands.
Late secretory phase = elongated/saw-toothed glands, spiral arterioles in stroma. Lots of secretions in glands.
If pregnancy does not occur, there is withdrawal of progesterone which causes the menstrual phase.
What changes can be seen histologically in the endometrium in this phase?
Haemorrhage within endometrial stroma, fragmentation of stroma and glands. Might see some mitotic figures.
What are the three layers of muscle of the myometrium?
Inner longitudinal
Middle circular
Outer longitudinal
How can you tell the difference between the endocervix and the ectocervix histologically?
Endocervix = loose fibromuscular stroma lined by simple columnar ciliated epithelium, with deep folded crypts.
Ectocervix = dense smooth muscle lined by non-keratinising stratified squamous epithelium.
The junction between endocervix and ectocervix varies in it’s position during life, with the cells changing between stratified squamous and simple columnar.
After menopause, is the junction likely to be above or below the external os?
Below the external os.
(in puberty and adults may lie on ectocervix, then lowers to level of os or endocervical canal after menopause)
What sort of epithelium would you find lining the vagina?
Non-keratinising stratified squamous epithelium.
Below the epithelium, the vagina has a stroma containing elastic fibres and a rich vascular network. Below this is a muscular wall.
What are the two muscle layers of the vagina?
Inner circular
Outer longitudinal
What sort of adventitia would be found in the outer layer of the vaginal wall?
Loose connective tissue.
When during menstruation would the epithelium of the vagina look spongy due to glycogen accumulation?
Around the time of ovulation.
What is the difference histologically between the labia majora and the labia minora?
Labia majora = keratinising stratified squamous epithelium (normal skin)
Labia minora = mostly non-keratinising stratified squamous epithelium.
What glands in females are analogous to the prostate in males, and are lined by pseudostratified columnar epithelium.
Lesser vestibular glands (Skene’s/periurethral glands)
