Case 14- Histology Flashcards
Relations of the Prostate
The Prostate envelops the prostatic urethra • Superior- bladder • Anterior- pubic synthesis • Posterior- ampulla of the rectum • Inferolateral- levator ani
Lobes of the Prostate
- Isthmus (anterior lobe)- anterior to the urethra, fibromuscular portion with little glandular tissue. The muscle fibres are an extension of the internal urethral sphincter.
- Right and left lobes- glandular portion. Can be subdivided into 4 lobes; inferoposterior, inferolateral, anteriormedial, superomedial.
Arterial supply to the prostate
Primarily the inferior vesicle artery but also the middle rectal and the internal pudendal artery
Venous drainage of the Prostate
The veins form the prostatic venous plexus. The veins drain into the internal iliac veins. The prostatic venous plexus connects with the vesicle venous plexus and the internal vertebral venous plexus. Through this malignant cells can travel.
Sympathetic innervation of the Prostate
Presynaptic innervation originates from the sympathetic trunk at T12-L3
Structure of the Prostate
The prostate is composed of secretory glands and ducts that open into the urethra. Surrounding these ducts is a stroma made up of fibroblasts, collagen and smooth muscle. The glands are surrounded by a fibromuscular capsule, which extend into the prostate as septa which separate the prostate into lobes. There is a thin lamina propria made of smooth muscle and collagen
The glands within the Prostate
- Inner periurethral - open directly into urethra, mucosal glands
- Outer periurethral - small ducts transfer secretion into urethra, submucosal glands
- Main prostatic/external - open into urethra via long ducts, the Peripheral zone glands
The Epithelium of the Prostatic glands
1) Columnar epithelium- tall or cuboidal
2) Flat basal cells in contact with the basal membrane- secretes acid phosphodase, citric acid and amylase
The Epithelium of the Prostatic ducts
Can be columnar or cuboidal. Towards the urethra the epithelium becomes more cuboidal and transitional (like the urethra)
Digital examination of the prostate
Done via the rectum, the malignant prostate feels hard and contains irregular nodules. Easier to palpate with a full bladder.
Enlarged prostates
Can cause urinating difficulties and retention. It may compress the prostatic urethra preventing urination. A suprapubic catheter can be used to drain urine. TURP is a surgical treatment for difficulty urinating with an enlarged prostate without incision.
Benign prostatic hyperplasia
Most common prostate disorder in older men. Enlargement of the mucosal and submucosal glands and an increase in fibromuscular stroma. The Periurethral glands (PUG) of the middle lobe compress the urethra.
Prostatic Adenocarcinoma
Occurs in glands at the periphery, often advanced before the patient notices
Fibromuscular structure of the cervix
70-80% collagen, 10-15% smooth muscle and <1% elastic fibre.
The 2 anatomical regions of the cervix
The endocervix and the ectocervix. The endocervix is the inner portion of the cervix that connects the uterine cavity to the vaginal cavity. The ectocervix projects into the vaginal cavity.
Microanatomy of the Endocervix
Lined by a single layer of tall columnar epithelium which secrete mucus. Mucus viscosity changes with the stage of the menstrual cycle, i.e. low viscosity at time of ovulation
Microanatomy of the Ectocervix
Stratified squamous epithelium, the cells appear pale due to glycogen
Microanatomy of the cervical stroma
Collagenous structure with some smooth muscle. Proximal cervix contains lots of smooth muscle which decreases towards the distal cervix. Collagen provides strength to the cervix.
Role of the cervical smooth muscle
Acts like a sphincter to maintain pregnancy
Cervical remodelling
Towards labour the cervix breaks down to allow for dilation
Vagina
Extends to the vestibule. A collapsed fibromuscular tube about 7-9cm ling
The 4 layers of the vagina
1) Stratified squamous epithelial mucosa- pale due to glycogen
2) Lamina propria (subepithelial region)- lots of elastic fibre and thin walled vessels
3) Fibromuscular layer
4) Adventitia
Layers of the vagina- Fibromuscular layer
Contains an inner layer of poorly organised encircling smooth muscle fibres and a outer layer of longitudinal muscle fibres.
Layers of the vagina- Adventitia
Composed of fibrocollagenous tissue containing thick elastic fibres, vessels, nerves and ganglion cells. At the lower portion the fibromuscular layer contains some skeletal muscle, which is mainly around the introitus.
Vagina transformation zone
The partial or complete replacement of the columnar epithelium of the endocervical canal by the stratified squamous epithelia of the vagina during puberty and the first pregnancy. The process is squamous metaplasia and causes instability in the area
The 3 cell types in the vagina transformation
- Original columnar/squamous epthelium
- Metaplastic squamous epithelium
- Atypical epithelium may have malignant potential
Histological changes that precede cancer in the transformation zone
• The cells lose their regular stratified pattern
• Have a high nucleus-to-cytoplasm ratio
• Show variation in shape and zone and increased mitotic activity
These changes are called Cervical Intraepithelial Neoplasia (CIN)
How to diagnose CIN
Can be diagnosed by cervical smear before it invades the basement membrane and becomes malignant (invasive cervical carcinoma). Can spread around the internal iliac lymph nodes and be surgically removed.
Invasive cervical carcinoma
Invaded the cervical stroma
Location of the Bulbourethral gland
Just below the membranous urethra
Structure of testes
The Seminiferous tubules are held within the Tunica Albuginea which is within the Tunica vaginalis which are made of peritoneum. The Seminiferous tubules drain into the Rete testes then then the Efferent ducts and Epididymis. The Epididymis connects to the Vas deferens.
Divisions of the testes
The tunica albuginea contains septa, which contains 250-300 lobules. Each lobules contains 1-4 seminiferous.
Where does the primitive sperm start to develop
The basal lamina
Leydig cells
Located in the interstitium. Synthesises testosterone, responds to LH
Sertoli cells
Located in the seminiferous tubules. Synthesis of hormones/ proteins. Responds to FSH. Supports cells for spermatogenesis.
Where are androgens produced
In the testes (95%) and adrenal glands (5%)
Steroidogenesis
Yields testosterone precursors
Types of androgens
Androstenediol, Adrostenenedione, DHEA, Testosterone. DHT (deydrotestosterone).
What can testosterone be converted into
1) Testosterone is made from cholesterol precursors (steroid pathway)
2) Testosterone binds to androgen receptors
3) The enzyme 5 alpha reductase reduces testosterone to DHT
4) DHT is a more potent form of testosterone and binds to androgen receptors
5) Testosterone is converted to Oestrogen by the enzyme Aromatose and binds to the oestrogen receptors
Testosterone production
In the Leydig cells
1) Cholesterol is converted to Pregenolone
2) Pregenolone can be converted to Progesterone by 3beta-HSD
3) Pregenolone is converted to DHEA then Androstenediol and finally Testosterone by 3beta-HSD
2 pathways of Testosterone
1) Testosterone -> enters blood stream -> testosterone targets tissue / the peripheral tissues convert to DHT and oestrogen.
2) Testosterone -> Enters seminiferous tubule -> Diffuses into seminiferous tubule and is required for Spermatogenesis.
What is required for Spermatogenesis
Testosterone concentration in the Seminiferous tubules must be 100 times more then in the blood stream
What is testosterone bound to
60% of testosterone is bound to SHGB (sex hormone binding globulin), 38% is bound to Albumin. 2% of testosterone is active and unbound. Free testosterone can bind to AR or be converted to DHT or oestradiol.
Function of Androgens
- Effects before birth- male genitalia formation
- Effects on reproductive organs- Spermatogenesis and semen production
- Secondary sexual characteristics- related to puberty (bone growth, facial hair, oil production). Reduces FSH
- Non- reproductive actions- primarily testosterone but the skeleton also requires oestrogen. Causes muscle mass and red blood cell production. Decreases HDL
Inhibin B
Is found only in men. It inhibits FSH production, it is a serum marker for testicular activity. May have tumour suppressor activity. If there are low concentration it can indicate fertility issues or a potential tumour.
Hypothalamic-Pituitary-Testicular axis
- The Hypothalamus produces GnRH which acts on the anterior pituitary.
- The anterior pituitary releases FSH and LH
- The FSH acts on the Sertoli cells causing increased Inhibin and Spermatogenesis
- When inhibin levels rise there is negative feedback and FSH levels reduce
- Increased LH acts on the Leydig cells and increase testosterone, which diffuses into the ST and peripheral targets.
- When Testosterone levels rise there is negative feedback and causes LH levels to decrease in the anterior pituitary and GnRH levels to decrease in the Hypothalamus
How often does the Hypothalamus secrete GnRH
Every 30 to 120 minutes in the blood
Diurnal variation in testosterone
Levels are highest in the morning and dip at 8pm
How does abuse of androgens cause a low sperm count
Intratesticular concentration of testosterone is not related to the negative feed back loop. Increased systemic androgens in circulation results in excessive negative feedback on hypothalamus and anterior pituitary.
Aromatase enzyme deficiency
- Deficiency- decreased oestrogen, cause tall stature (late fusing of the long bones at the epiphyses), Osteoporosis.
- Overproduction- increased oestrogen, increased adipose tissue. Causes feminine features, breast development, decreased facial hair, altered pubic distribution.
5 alpha-reductase 2 inhibitors
- 5 alpha-reductase 2 converts testosterone to DHT.
- DHT has strong growth promoting effects on its target organs.
- 5 α-reductase-2 inhibitors stop production of DHT
- Benefits people with prostatic hypertrophy and prostatic cancer
The tissues testosterone targets
Muscle, liver, fat and skeleton
