What type of tissue is the anterior and the posterior pituitary?
Anterior - Endocrine gland Posterior - Nervous tissue
What is secreted by the anterior pituitary?
Glycoproteins hormones - FSH, LH, TSH Polypeptide hormones - GH, ACTH, Prolactin
What is secreted by the posterior pituitary?
ADH Oxytocin (although produced in the hypothalamus)
Describe in general how FSH and LH are released?
Gonadotrophin Releasing Hormone is released by the hypothalamus which travels by the hypophyseal portal circulation to the anterior pituitary. The amount of FSH and LH released is directly correlated to the amount of GnRH released.
What is the general action of LH and FSH?
Act on the gonads and control gamete production and stimulate secretion of the gonadal steroid. E.g. testosterone, oestrogen, progesterone.
In the male how are FSH and LH levels altered?
Testosterone acts as a negative feedback mechanism by reduces the amount of GnRH that is secreted.
In the female how are FSH and LH levels altered?
Moderate levels of oestrogen reduce GnRH secretion via negative feedback mechanisms. High levels of oestrogen increase the amount of LH and FSH secretion. High levels of oestrogen and progesterone prevent the high levels of LH and FSH. (however as inhibin is present only LH rises)
Describe the HPA in the male:
Testosterone levels must be kept constant in the male as spermatogenesis is constant. LH and FSH are released by the anterior pituitary in response to GnRH. FSH binds to Sertoli LH binds to Leydig Testosterone is produce by Leydig cells in response to LG but can only pass into seminiferous if FSH has been primes by FSH. Inhibin is released by Sertoli cells in response to the amount of spermatogenesis that occurs. Inhabit acts on the pituitary gland to prevent FSH production. Testosterone is produced in Leydig cells but inhibits GnRH release, this keeps testosterone at constant levels.
How do testosterone levels fluctuate?
Testosterone levels are highest in the morning. Testosterone levels are also affected by environmental stimuli.
Describe what occurs during the follicular phase:
Follicles are only partially developed therefore little oestrogen or inhibin is produced. Progesterone levels are also low. There is little inhibition at the pituitary so FSH and LH rises. FSH binds to granulosa cells and stimulate follicle development. They also stimulate inhibin release. LH stimulates the theca interna and this causes the secretion of oestrogen. As the follicle grows there is an increase in oestrogen and inhibin secretion. This results in increased LH levels (but not FSH as inhibin is preventing its release - need low FSH levels so another follicle is not stimulated to develop) the LH surge triggers ovulation.
Describe what occurs during the Luteal Phase:
After ovulation a corpus luteum forms spontaneously. The corpus luteum secretes oestrogen and progesterone. Progesterone prevents the positive feedback loop of oestrogen on the gonadotropin so FSH and LH levels are low. Also inhibin levels are still high so FSH levels are low (again you don't want another follicle developing) after 14 days precisely the corpus luteum dies. There is a drop in oestrogen and progesterone stimulating the menses. This drop in hormones then causes FSH and LH levels to rise again and follicular development begins again.
What is the interval between ovulation and do menses?
List the stages of the menstrual cycle:
Preparation Ovulation Waiting - exactly 14 days
Describe the following chart:
During the follicular phase of the ovarian cycle FSH andLH promote the developing follicle. As the follicle grows the level of oestrogen increases due to increasing granulosa and theca interna cells.
As inhibin levels rise due to stimualtion by FSH (inhibin is released by granulosa cells) they inhibit FSH release so it decreases. As oestrogen levels continue to rise due to LH release is stimulated. This results in an LH surge and ovulation occurs.
During the luteal phase the follicle under influence of high LH becomes the corpus luteum. Oestrogen and now progesterone are produced by the corpus luterum however less oestrogen than before was generated by the corpus luteum.
Progesterone and oestrogen present prevent the FSH and LH release. Progesterone stimulates the uterine lining in preparation for pregnancy. It stimulates the development of spiral arteries and stimulates secretion from glands. It also reduced contractilty of myometrium (Prevent embryo expulsion)
After 14 days the corpus luteum dies. Progesteron adn oestrogen levels drop, this stimualtes the menses. It also allows FSH and LH levels to rise again and so follicular development can start to occur and the cycle begins again.
What maintains the corpus luteum is the egg is fertilised?
The blastocyst produces human chorionic gonadotrophin which is structurally similar to LH so it maintains the corpus luteum so it carries on producing hormones until the placenta develops.
The hormones are needed to maintain the endometrial lining.
Describe the microscopic structure of the ovary:
Has a cortex and medulla.
Its outer surface is covered by squamous epithelium - a layer of peritoneum - or broad ligament
At one pole of the ovary is the hilum where the artery vein and nerve exit.
The cortex of the medulla contains germ cells in numerous stages of development.
Describe a primordial follicle
An oocyte with a single layer of granulosa cells surrounding it.
Describe a primary follicle:
An oocyte with a zona pellucida surrounding it. Then several layers of granulosa cells. Then outside the stromal cells differentiate into theca follicula.
Describe a secondary follicle:
The theca folliculi differentiate into theca interna and externa. Fluid filled spaces devleop between the granulosa cells.
Describe a tertiary follicle:
The fluid filled spaces move towards the periphery and an antrum develops. The oocyte is surrounded by a few layers of granulosa cells calles the coronar radiata.
Describe a Graafian follicle:
The oocyte with its surrounding granulosa cells (corona radiata) is attached to the rest of the granulosa cells via the cumulus oophorus a peg of granulosa cells. This loosens prior to ovulation so that the occyte and corona radiata floats free in the antral fluid.
What happens to granulosa and theca interna cells after ovulation?
Granulosa cells become granluosa lutein cells which produce progesterone.
Theca interna cells theca lutein cells which produces oestrogen.
Describe the different parts of the fallopian tube:
Fimbria - catch the ovum - not attached the ovary
The infundibulum - bell shaped area that joins the fimbria to the ampulla
Ampulla - wide section where fertilsation normally occurs
Isthmus - narrowing where the ampulla connects to the uterus
Intramural - within the uterine wall
Describe the wall of the fallopian tube:
Columunar epithelium with varying degrees of folding, glands, and cilia.
As you approach the uterus there are more peg cells- mucous secreting and fewer ciliated cells.
The most folded area is in the ampulla.
Muscular layer - 2 layers in the ampulla and 3 in the isthmus.
Serosal covering - broad ligament
Describe the layers of the uterus.
Endometrium - Lined by simple columnar epithelium and has a lamina propria. The lamina propria contains glands/connective/stromal elements.
The endometrium can be further divided into the stratum fucntionalis and stratum basalis. With the stratum functionalis being divided further into outer compact and deeper spongy layers.
Myometrium - Has 4 poorly defined muscle layers.
Describe the blood supply to the uterus:
The uterus recieves blood supply from uterine arteries which form arcuate arteries in the myometrium.
The arcuate arteries then give rise to two sets of the branches:
Straight arteries which supply the stratum basalis
Coiled arteries which supply the stratum functionalis.
Describe the changes that happen to the endometrial lining during the proliferative phase:
Stratum functionalis regenerates from the cells lining the glands in the stratum basalis which remains intact during menstruation. The growth of S.functionalis also leads to increasing length of the endometrial glands. Cells surrounding the glands - stromal cells also develop and proliferation to fill the spaces between the glands.
This regeneration is under the influence of oestrogen.
Describe the changes that occur in the endometrium in the secretory phase:
Progesterone stimulates the endometrium to develop further. The glands devleop further and become coiled. The stroma becomes oedematus and the stromal cells develop into decidual cells. If fertilsatiion occurs decidual cells contribue to the formation of the placenta and produce prolactin.
Describe the changes that occur to the endometrium during the menstrual phase:
Progsterone and oestrogen levels drop. The lack of progesterone leasd to spasm of the spiral arteries. The stratum functionalis is derived of nutrients and dies. This spasm is due to locally produced prostaglandins.
The stratum functionalis is not shed as the coiled arteries do not go into spasm.
Describe the cervix:
Entrance is via the Internal Os and exit via the External Os with the cervical cavity between the two.
The cervix is lines by simple columnar epithelium which contains mucous secreting glands. However on the inner aspect of the internal Os there is an abrupt change in the epithlium to stratified squamous epithelium. This is called the squamocolumnar junction and is where the majority of neoplasms occur.
Describes the structure of the vagina:
Fibromuscular tube that connects the cervix to the exterior.
Mucosa - stratified squamous non-keratinised epiethlium. No glands.
Muscular layer containg smooth and skeletal muscle.
The vagina lacks glands so how is it lubricated?
By mucus produced by glands in both the cervix and the vestibule.
What generates the acidic environment of the vagina?
Under the influence of oestrogen the epithelial cells accumulate glycogen which is a substrate for lactobacillus to produce lactic acid which causes a low pH.
Describe breast tissue at puberty:
Under influence of increasing oestrogens the breast enlarges due to deposition of adipose and the duct system becomes much larger.
At this stage the secretory portions are poorly developed and surrounded by myoepithelial.
What changes occur to the breasts during the menstrual cycle?
The mammary glands are stimulated by the oestrogen peak during each cycle which induce duct proliferation and lead to enlargements adn sometimes oedema and tenderness.
What changes are seen to breast tissue during pregnancy?
Oestrogen causes proliferation of the duct system.
Progesterone influences development of secretory tissues.