Histology - SUGER Flashcards
What are the four parts of the urinary tract?
- Kidneys
- Ureters
- Bladder
- Urethra
What are the three main parts of the kidney?
- Cortex
- Medulla
- Pelvis
What do we primarily find in the renal cortex?
Glomeruli, proximal convoluted tubules and distal convoluted tubules
What is a medullary ray? Where is it found?
- A collection of loops of Henle and collecting ducts
- Specialised area within the renal cortex
What does the renal medulla comprise?
Loops of Henle and collecting ducts of nephrons both close to and far away from the capsular surface of the kidney
What are nephrons? Where does the nephron start? What is the glomerulus lined by? What is the glomerulus encased by?
- Each kidney made up of ~million filtering units called nephrons, each includes a glomerulus (filter) and a tubule
- Nephrons start at glomerulus (a tuft of fenestrated capillaries)
- Glomerulus lined by podocytes
- Glomerulus encased by Bowman’s capsule
- White space on diagram is where filtrate forms from glomerulus
What are the two main cell types within the glomerulus?
- Capillary endothelial cells
- Mesangial cells
- PAS allow us see basement membrane here
What do mesangial cells comprise? What is their function?
- Mesangial cells comprise smooth muscle
- Provide structural support for capillary in its production of extracellular matrix protein. Contraction of this smooth muscle reduces glomerular filtration rate
The glomerular basement membrane comprises three layers. What are these? What is the basement membrane lined by on its inner surface?
- Glomerular capillary wall
- Basement membrane
- Foot processes of podocyte
- Capillary basement membrane lined on its inner surface by vascular endothelial cells that are fenestrated, these are bridged by fibrils that prevent passage of large molecules, e.g. albumin
What does an epithelial basement membrane contain? How about a glomerular basement membrane?
- Epithelial basement membrane = lamina lucida + lamina rarer
- Glomerular basement membrane = lamina lucida interna, double thickness lamina densa + lamina lucida external (two basement membranes back to back). Also contains collagen + negatively charged heparin sulphate molecules
Magnified image of the glomerular basement membrane.
What is the juxtaglomerular apparatus? What are its two components?
- Next to glomerulus
- 2 components: one from afferent arteriole and one from distal convoluted tubule
What is the role of the juxtaglomerular apparatus? What are the three types of cells in the juxtaglomerular apparatus?
- Juxtaglomerular apparatus emulates function of each nephron, it is next to the glomerulus
- Macula densa
- Juxtaglomerular cells (secrete renin)
- Lacis cells
Where can we find the proximal convoluted tubule? What is it lined by? What is its role?
- Renal cortex
- Lined by simple cuboidal epithelium
- Reabsorption of solutes
Next is the loop of Henle. What does this do? What are its two parts? What is it lined by?
- Concentration of urine
- Dsecending and ascending limbs
- Thin segment lined by simple squamous epithelium
- Thick segment lined by low cuboidal epithelium
Next is the distal convoluted tubule. What is its function? What is it lined by?
- Reabsorption of more water and solutes
- Lined by low cuboidal epithelium
From the distal convoluted tubules, urine drains into the collecting ducts. What is their function? What are they lined by? What are the two types of epithelial cell that it contains?
- Water reabsorption and controlling acid-base and ion balance
- Cuboidal epithelium
- Principal cells and intercalated cells
What is the blood supply to the kidney?
Diagram of blood supply to kidney.
What is the renal corpuscle?
Whole unit of glomerulus and Bowman’s capsule
Once blood has left the glomerulus, where does it pass to?
- Passes to efferent arteriole, which then gives rise to peritubular capillaries
- As it descends into medulla, gives rise to vasa recta –> renal veins –> back into inferior vena cava
The collecting ducts in the medulla drain into the renal pelvis. What is the renal pelvis? What is it lined by?
- Transmits filtrate from nephron to ureter
- Lined by urothelium
What is urothelium?
Another diagram of urothelium.
The only cells we can be confident are not in contact with the basement membrane are the umbrella cells
What are ureters? What are they lined by?
- Muscular tubes that convey urine via peristalsis from the kidney to the bladder
- Lined by the same urothelium as is found in the renal pelvis
What is the bladder formed by?
Bladder drains through the urethra
What is the urethra like in females?
What is the urethra like in males?
Divided into three parts
Afferent arteriole
What are the functions of the skin?
- Barrier to infection
- Thermoregulation
- Protect against trauma
- Protect against UV light
- Vitamin D synthesis
- Sensation
What are the three layers of the skin?
What is the epidermis made up of?
- Stratum basale = single layer of cells that rest on a basement membrane (which is made up of type IV collagen)
- Stratum basale contains melanocytes (synthesise melanin and transfer it to surrounding keratinocytes, absorb UV light as well) and basal epithelial cells
What is the second layer of the epidermis? What does it contain?
- Stratum spinosum
- Comprises plump polygonal keratinocytes (bound together by desmosomes), Langerhans cells and Merkel cells
What is the third layer of the epidermis? What is it made up of?
- Stratum granulosum
- Comprises a layer of flattened squames, which have an eosinophilic cytoplasm that contains haemotoxophilic kerato-hyaline granules
- Keratin forms in this layer, keratinocytes mature and they die as their cytoplasm becomes filled with keratin-hyaline granules
What is the outermost layer of the epidermis?
- Stratum corneum
- Acellular layer of skin comprising plates of keratin in the form in dead, keratinised squames
On the palms and soles, what is the extra epidermis layer between the stratum granulosum and the stratum corneum?
- Stratum lucidum (only present in thick skin; palms and soles)
The epidermal epithelium specialises to form a number of specialised what? What do these contain?
- Specilaises to form a number of specialised epidermal adnexae. These are downgrowths of the epidermis into the dermis. They include:
- hair follicles
- sebaceous glands
- eccrine sweat glands
- apocrine sweat glands
What do sebaceous glands accompany? What do they do?
- Accompany hair follicles
- Produce sebaceous secretions which lubricate and waterproof hairs
- Holocrine secretion
What do apocrine glands accompany? What do they do?
- Accompany hair follicles
- Found in the armpits, groin, genitals and the anus
- Simple coiled tubular glands that produce their secretion though apocrine secretion. Function uncertain but probably pheromone secretion
What are the eccrine glands?
- Thin watery secretion
- Everywhere
- Coiled tubes, 2 cell layers thick - inner secretory, outer myoepithelial
- Eccrine (merocrine) secretion
What is the junction between the epidermis and dermis?
Dermo-epidermal junction, ridged
The dermis is the connective tissue layer underling the epidermis. What are its two components?
- Papillary dermis
- Reticular dermis
- Dermis comprises fibrous connective tissue containing elastin, blood vessels, nerves, and the downgrowth of adnexal organs of the epidermis
What does the dermis contain?
What are Meissner’s corpuscles?
Mechanoreceptors. Formed by connective tissue capsule that comprises several lamella of Schwann cells. Centre of capsule contains one or more afferent nerve fibres, play a role in fine touch
What are Pacinian corpuscles?
Large encapsulated nerve endings located in subcutaneous tissue. Differ from Meissner’s corpuscle in their morphology, distribution, and response threshold. Fluid-filled space separates lamellae. One or more rapidly adapting afferent axons lie at centre. High frequencies. Adapt more rapidly and have a lower response threshold
What lies beneath the dermis? What does this comprise? What is its function?
- The subcutis
- Comrpises adipose tissue and fibrovascular septa
- Insulation, shock-absorbed, food store
What is the breast comprised of? How does it differ in males?
- Myoepithelial system of ducts and lobules set in fibroadipose connective tissue
- Males only have ducts
What is the functional unit of the breast?
- Terminal duct lobular unit
What are the ducts and lobules lined by in the breast?
- Two layers:
- outer myoepithelial
- inner columnar epithelial
What happens to the cells of the breast during lactation?
Inner layer of secretory cells become vacuolated
What is the epithelium of the skin? What is it mainly comprised of? Does darker skin mean more melanocytes?
What are lactating, non-lactating and lactiferous ducts?
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The testis is surrounded by three layers to form a capsule. What are these three layers?
- Tunica vaginalis (layer of mesothelial cells resting on a basement membrane, has a parietal + visceral layer)
- Tunica albuginea
- Tunica vasculosa
What is the tunica vaginalis comprised of?
Flattened layer of mesothelial cells
What is the tunica albuginea comprised of?
Collagen fibres with some fibroblasts, myocytes + nerve fibres
What is the tunica vasculosa comprised of?
Loose connective tissue containing blood vessels + lymphatics
What is the parenchyma of the testis?
Divided into lobules by septa, each lobule contains 1-4 seminiferous tubules
Which cells do the seminiferous tubules contain?
Germ cells and Sertoli cells
What are the different germ cells in the seminiferous tubules?
- Spermatogonia (three types: type Ad = darkly stained stem cells, type Ap = pale stained + type B = spherical nuclei with densely stained masses of chromatin)
- Primary spermocyte
- Secondary spermocyte
- Spermatid
- Spermatozoon
What shape are Sertoli cells? Where do they rest? What is their function? What is the shape of their nuclei?
- Columnar cells on the basement membrane of the tubule
- Send cytoplasmic projections around the germ cells. Have supportive, phagocytic + secretory functions
- Nuclei are irregularly shaped, folded + have a prominent nucleolus
What are the three parts of spermatozoa? What does each part contain?
- Head = acrosomal cap, nucleus
- Midpiece = spiral mitochondria
- Tail = neck, axoneme, plasma membrane
Where are Leydig cells found in the testis? What do they contain? What do they produce?
- Present in the interstitium between tubules
- Abundant cytoplasm rich in lipid, contains Reinke’s Crystalloids
- Produce testosterone
The Leydig cells discharge their contents into the rete testis. Where are these found? What is their function? What are they lined by?
- Anastomosing network of tubules at the hilum of the testis
- Receive luminal contents from seminiferous tubules and act as a mixing chamber for them
- Lined by simple squamous or low columnar epithelium on a relatively thick basement membrane
The rete testis discharges its contents via efferent ducts. What are these? What are they lined by?
- Convoluted tubules which empty into the epididymis
- Lined by ciliated and non-ciliated simple columnar epithelium with interspersed cuboidal cells giving a pseudostratified appearance
What is the epididymis lined by?
Columnar cells with long atypical cilia supported by a thick basement membrane
The contents of the epididymis are discharged into the vas deferens. What happens to the distal part of the vas deferens? What is the vas deferens lined by? How many layers thick is its muscular wall?
- Distal part enlarged to form the ampulla which joins the excretory duct of the seminal vesicle to form the ejaculatory duct
- Lined by pseudostratified columnar epithelium comprising columnar + basal cells
- Has a thick muscular wall of 3 layers
What is the shape of the prostate gland? What does it surround? What are its 5 lobes?
- Pear shaped glandular organ
- Surrounds bladder neck + prostatic urethra
- Anterior, middle, posterior + two lateral lobes
What is the prostate gland covered by? What are its two components?
- Covered by fibro-connective tissue capsule
- Glandular + non-glandular components
What are the acini in the prostate lined by?
- Acini are lined by secretory cells, basal cells and neuroendocrine cells
- Secretory cells secrete PSA + PAP into the seminal fluid
- Basal cells form a continuous layer
- Cells rest on a basement membrane
What does the stroma of the prostate gland contain?
- Smooth muscle
- Fibroelastic fibres
- Blood vessels
- Nerves
What are the seminal vesicles lined by? What do the seminal vesicles empty into?
- Lined by tall non-ciliated columnar epithelium
- Seminal vesicles empty into the ejaculatory duct, comprises majority of ejaculate
What are the 3 components of the erectile tissue of the penis? What do they all comprise?
- Left and right corpora cavernosa on the dorsal side
- Corpus spongiosum on the inferior side
- Erectile tissue comprises irregular vascular spaces separated by fibroelastic tissue + smooth muscle
What is this?
Seminiferous tubule
What is this?
Epididymis
What is this?
Vas deferens
What is this?
Seminal vesicles
What are the ovaries? What are their attachments?
- Organ that produces an ovum
- Attachments: to the broad ligament by mesovary, to the uterus by utero-ovarian ligament and to the pelvic wall by the suspensory ligament
What is the ovary covered by? What else does it contain beneath that? What is the stroma divided into?
- Covered by single layer of mesothelium
- Underneath it has tunica albuginea
- Underneath there is stroma - divided into cortex and medulla
What do the ovarian cortex and medulla comprise? What is present at the hilum?
- Ovarian cortex = spindle stroma cells, ovarian follicles and some leutinised cells
- Ovarian medulla = loose fibroelastic tissue with blood vessels, lymphatics and nerves
- Rete ovarii is present at the hilum
What do follicles in the ovary begin like? Where are these found? What do these comprise?
- Primordial follicles
- Located at the periphery of the cortex
- Contains primary oocyte in a resting state surrounded by a single layer of granulosa cells
What do the primordial follicles firstly develop into? Which hormone stimulates this? What changes shape?
- Primary follicles
- FSH stimulates follicular development
- Follicular epithelial cells and oocyte enlarge
- Zona pellucida forms directly around the oocyte
What do primary follicles develop into? What changes?
- Primary follicles develop into secondary follicles
- Granulosa cells proliferate and spaces form between these (will form follicular antrum)
- 2 layers form around the granulosa cells: theca interna (secrete oestrogen via stroma cells) and theca externa
During the menstrual cycle, only a few number of follicles will fully mature. What type of follicle is this? How do these appear?
- Mature (Graffian) follicles
- Ovum surrounded by a thick zona pellucida
- A layer of granulosa cells surround the oocyte - corona radiata
What happens the follicle at ovulation? Which hormone causes this?
- Ovulation triggered by LH
- Follicle converted into corpus luteum
- Leutinisation of the granulosa + theca cells occurs (become polygonal, larger in size, have abundant cytoplasm containing lipid)
- Secrete progesterone + oestrogen
- Regress if pregnancy doesn’t occur
When does regression of the corpus luteum occur? What happens to the cells? What forms?
- Regression starts 8-9 days after ovulation of pregnancy does not occur
- Granulosa cells decrease in size, develop pyknotic nuclei + accumulate abnormal lipid
- Cells undergo dissolution + are phagocytosed
What is the end result of corpus luteum regression? What does this comprise? What happens to these?
- Corpus albicans
- Comprises densely packed collagen with occasional follicles
- Eventually they may be resorbed or replaced by ovarian stroma
Where is the Fallopian tube found? What is its function?
- Fallopian tube runs throughout the length of the broad ligament
- Transports ovum to the uterus
- Fertilisation occurs here
What are the 4 segments of the Fallopian tube?
- Intramural
- Isthmus
- Ampulla
- Infundibulum
How is the mucosa of the Fallopian tube arranged? What are the two types of Fallopian tube epithelial cells?
- Mucosa is thrown into branching folds (plicae)
- 2 cell types: secretory and ciliated
What are the two layers of the muscularis of the Fallopian tube?
- Inner circular layer
- Outer longitudinal layer
What is the serosa of the Fallopian tube comprised of?
Connective tissue covered by mesothelium
What are the three layers of the uterus?
- Endometrium
- Myometrium
- Serosa
What are the two layers of the endometrium of the uterus?
- Stratum basalis - acts as a reserve of stromal and endometrial epithelial cells from which the endometrium will be replenished during the next menstrual cycle
- Stratum spongiosum - lost during each menstrual cycle unlike stratum basalis
What is the first half of the menstrual cycle known as? What is the endometrium responding to during this stage? What happens to the endometrium?
- Proliferative phase
- Responds to oestrogen stimulation
- Proliferation, no luminal secretions
After ovulation, what stage does the endometrium enter? What is this stimulated by?
- Secretory phase
- Stimulated by progesterone
What are the three parts of the secretory phase?
- Early = sub-nuclear glycogen vacuoles in the epithelial cells of the endometrial glands
- Mid = vacuoles above and below the nucleus and later intraluminal secretions, glands more rounded
- Late = endometrial glands have saw-toothed appearance with more intraluminal secretions
If pregnancy does not occur, what stage is after the secretory phase? What is this caused by? What is this stage characterised by?
- Menstrual phase
- Progesterone stimulation withdrawal
- Stromal haemorrhage and granulocytes
- Stromal and glandular fragmentation
What three layers of muscle does the myometrium comprise?
- Inner longitudinal
- Middle circular
- Outer longitudinal
What is the endocervix lined by?
- Loose fibromuscular stroma lined by simple columnar ciliated epithelium
- Thrown into crypts
What is the ectocervix lined by?
- Dense smooth muscle stroma lined by non-keratinised stratified squamous epithelium
- Site of squamocolumnar junction varies (between ectocervix and endocervix)
What is the vagina lined by? What does the stroma of the vagina contain? What are the muscle layers of the vagina?
- Vagina lined by non-keratinising stratified squamous epithelium
- Stroma contains elastic fibres + a rich vascular network
- Muscular wall = inner circular and outer longitudinal
- Loose connective tissue
What does the vulva comprise?
Mons pubis, clitoris, labia minora, labia majora, vulvar vestibula, hymen, urethral meatus, Skein’s gland, Bartholins gland, introitus
What are the labia majora and labia minora lined by?
- Labia majora = lined by keratinising stratified squamous epithelium and has skin adnexae
- Labia minora = mostly non-keratinising stratified squamous epithelium
What are Bartholin’s glands? What are minor vestibular glands?
- Bartholin’s glands = tubuloaveolar glands, acini lined by mucus-secreting epithelium
- Minor vestibular glands = simple tubular glands lined by mucus-secreting epithelium
What are Skein’s glands lined by? What is the hymen lined by? What is the clitoris?
- Skein’s glands = lined by pseudostratified columnar epithelium
- Hymen = lined by non-keratinising squamous epithelium
- Clitoris = erectile tissue rich in blood vessels and nerves
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What are the common features of all endocrine organs?
- Glandular epithelium (except posterior pituitary gland)
- Richly vascularised as secrete directly into circulation
- Secrete a variety of hormones
- Controlled by +ve and -ve feedback loops
What is the role of the pituitary gland? What are the two components?
- Coordinates the endocrine organs through feedback loops
- 2 components: posterior pituitary (downgrowth of hypothalamus) and anterior pituitary (epithelial structure)
What does the posterior pituitary comprise? What does it store/secrete?
- Neural tissue = axons with supporting glial cells
- Stores and secretes oxytocin and antidiuretic hormone
What does the anterior pituitary comprise?
- Comprises nests of epithelial pituicytes supported by a richly vascular fibrous stroma
- Several types of pituicytes
What are the most common pituicytes? How about the rest? What do they secrete?
- Somatotrophs (50%) secrete growth hormone
- Lactotrophs (25%) secrete prolactin
- Corticotrophs (15 - 20%) secrete variety of hormones, e.g. ACTH
- Gonadotrophs (10%) secrete FSH and LH
- Thyrocytes (1%) secrete TSH
Anterior pituitary under reticulin stain.
Reticulin surrounds a nest of pituicytes
Where are somatotrophs predominantly found?
Predominantly found in lateral wings of anterior pituitary
What shape are lactotrophs? What is distinct about them?
- Polygonal cells
- Cytoplasmic processes (brown) wrap around other cells
What do thyrotrophs looks like?
- Chromophobes (don’t particularly react with haemotoxylin or eosin)
- Elongated cytoplasmic processes
What shape are gonadotrophs? What can we stain them with?
- Scattered round/oval cells
- Stain with either:
- alpha subunit
- beta LH
- beta FSH
What shape are corticotrophs? What colour do they stain on haemotoxylin and eosin? Whereabouts are they found? What do they have within the cytoplasm?
- Round basophilic cells
- Stain purple with H+E
- Found towards the median of the gland
- Have large cytoplasmic vacuoles
What are the pituicytes supported by?
Sustentacular cells
Somatotrophs vs lactotrophs in electron microscopy.
Where is the pineal gland located? What does it comprise? What do these secrete?
- Just below the posterior end of the corpus callosum
- Comprises lobules of pinealocytes, secrete melatonin in response to
What does the thyroid comprise? What does it produce?
- Comprises a combination of follicular cells and colloid
- Produces thyroxine (follicular cells) and calcitonin (c cells)
Diagram of the histology of the thyroid gland.
How many parathyroid glands are there? Where are they located? What do they produce? What are the three cell types that are found within them?
- 4 parathyroid glands, variably located in the neck
- Produce parathyroid hormone (PTH)
- 3 cell types: chief cells, oxyphils and adipocytes
What shape are the chief cells? What do they secrete?
- Polygonal cells
- Scant cytoplasm
- Secrete PTH which raises the serum Ca2+
How can tell the difference between thyroid and parathyroid?
Parathyroid contains no calcium oxalate crystals (unlike thyroid)
What shape are oxyphil cells? What happens to their numbers with age? What do they contain?
- Large polygonal cells
- Increase with age
- Abundant eosinophilic cytoplasm
- Finely granular
What does the endocrine pancreas comprise? Where are these cells most prevalent? What are they surrounded by?
- Endocrine pancreas comprised islets of Langerhans
- Most prevalent within the pancreatic tail
- Balls of cells surrounded by a thin fibrous capsule
What do the cells of the islets of Langerhans secrete? Can you distinguish these cells on H+E?
- Beta cells (70%) = insulin
- Alpha cells (20%) = glucagon
- Delta cells (5 - 10%) = somatostatin
- PP cells (1 - 2%) = pancreatic polypeptide
- You can’t distinguish these cells on H+E
What are the 3 layers of the adrenal cortex? What do these secrete?
- Zona glomerulusa (outermost layer) = secretes mineralocorticoids
- Zona fasciculuta = secretes glucocorticoids
- Zona reticularis (innermost layer) = secretes androgenic steroids
Is the zona glomerulusa a complete layer? What does it comprise?
- Thin, incomplete layer
- Comprises small cells with vaculolated cytoplasm
What does the zona fasciculata comprise?
Comprise large polygonal cells with an almost clear cytoplasm
What does the zona reticularis comprise?
Comprises anastamosing columns of small polygonal cells
What is the adrenal medulla comprised of? What does it secrete?
- Comprised of large, polyhedral chromaffin cells
- Secretes adrenaline and noradrenaline
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