Endocrinology & Reproduction Flashcards
-To maintain homeostasis, the body uses ?
Chemical messengers
Define Autocrines?
Autocrines are chemical messengers that control the source cell that secrete them.
They are also called intracellular chemical mediators.
List the examples of autocrines you know?
- Leukotrienes
- Cytokines
- Interleukin
All 3 of these , are secreted by monocytes in response to external stimuli.
What are Paracrines?
Paracrines are chemical messengers that diffuse from control cells to the target cells through the interstitial fluid and affect neighbouring target cells through gap junctions.
They are also called Juxtacrine messengers.
List the examples of paracrines you know?
- Prostaglandins
- Histamine
- Bradykinin
What are Neurotransmitters?
Neurotransmitters are endogenous signaling molecules that carry information from one nerve cell to another cell or muscle.
List examples of neurotransmitters you know?
- Acetylcholine
- Dopamine
- Adrenaline
What are Endocrines?
Endocrines are synthesized by endocrine glands. They are hormones, circulated in the blood to target cells
Examples of hormones?
- Insulin
- Growth hormone
- Cortisol
List the examples of Neuro Endocrines?
- ADH
- oxytocin
_________ acts as a neurotransmitter and paracrine messengers simultaneously
Histamine
List the classes of hormones
- Steroid hormones
- Protein hormones
- Tyrosine derivatives
Briefly talk about steroid hormones?
Steroid hormones are synthesized from cholesterol or derivatives. They include ask the hormones of the adrenal cortex, gonads and some from the placenta.
Briefly explain protein hormones?
Protein hormones are made from large or small peptide. They include all the hormones secreted by the pituitary gland, parathyroid gland, pancreas and a the placenta.(the 4P’s) and Hypothalamus
Talk about the hypothalamus
The hypothalamus is located in the ventral diencephalon, just below the thalamus. It is formed by several nuclei scattered in the walls and floor of the 3rd ventricle. It extends from the optic chiasma to the mammilary body.
Briefly talk about tyrosine derivatives?
Tyrosine derived hormones are synthesized from amino tyrosine.
Examples include: Thyroid hormones and Adrenal medulla.
The nuclei of the hypothalamus are divided into 3 groups, name them?
- The anterior or preoptic group: include; the preoptic, suprachiasmatic, paraventricular, anterior & supraoptic nuclei
- Middle or tuberal group: includes; Dorsomedial, Ventromedial, lateral, arcuate (tuberal) nuclei
- Posterior or mamillary group: includes; posterior, mamillary nuclei
Which parts of the hypothalamus are associated with the pituitary gland and Neuroendocrine effects?
- Paraventricular
- Supraoptic
- Arcuate,
Are the only nuclei associated. This is because they contain magnocellular neurosecretory neurons which secrete oxytocin and ADH (Anti-Diuretic Hormone).
They are however transported and stored in herring bodies in the posterior pituitary until stimulus arrives for their release.
What is the role of the arcuate nucleus of the hypothalamus?
The arcuate nucleus in the cineureum controls the inhibition and secretion of the hormones from the anterior pituitary.
What are hypophysiotropic hormones?
Hypophysiotropic hormones are hormones that release or inhibit other hormones.
Examples include;
1. Growth hormone releasing hormone (GNRH)
2. Growth hormone inhibitory hormone(GNIH)
3. Thyrotropin releasing hormone (TRH)
4. Corticotropin releasing hormone (CRH)
5. Gonadotropin releasing hormone (GRH)
6. Prolactin inhibitory hormone (factor)
All Hypophysiotropic hormones are transported to the anterior pituitary gland via?
Hypothalamo-Hypophyseal portal vessels
Talk about the pituitary gland?
Also called Hypophysis, it is a small endocrine glands with a diameter of 1cm and weight less than 1gram.
It is located in the sphenoid bone, at the base of the skull, in a depression called Sella Turcica
The pituitary gland is divided in two, what are their names?
- Adenohypophysis (anterior pituitary)
- Neurohypophysis (posterior pituitary).
They both develop from different sources embryologically.
Histologically, the anterior pituitary has 2 types of cells, name them;
- Chromophobes (lack granule and stain poorly)
- Chromophils (have granule, have affinity for stains)
Chromophils are further sub divided into 2
1. Acidophiles,
2. Basophiles.
What does each secrete respectively
Acidophiles secrete somatotropin(growth hormone) & prolactin
Basophiles secrete ACTH,thyrotropes (TSH)& Gonadotropin (FSH & LH)
List all the hormones secreted by the anterior pituitary?
- Follicle stimulating hormone
- Luteinizing hormone
- Adrenocorticotropic hormone (ACTH)
- Thyroid stimulating hormone
5.Growth hormone (somatotropin) - Prolactin
Hormones such as FSH, LH,ACTH,& TSH are called tropic hormones. This means that?
It means that they stimulate other endocrine glands
What is somatotropin
Somatotropin also known as Growth hormone, is secreted by somatotropes present in the acidophilic cells of the anterior pituitary.
Somatotropin acts to increase bone length & thickness,
Growth hormone is stimulated by ?
GHRH(Growth hormone releasing hormone), hypoglycemia, fasting/starvation,exercise, stress, trauma, initial stages of sleep.
Growth hormone is inhibited by ?
GHIH(Growth hormone inhibiting hormone), hyperglycemia, increased fatty acid in the blood, later stages of sleep
Growth hormone functions through somatomedin. Discuss?
Somatomedin Is secreted by the liver. It is important because, even if growth hormone level is normal, If somatomedin is deficient, dwarfism would still occur
How long can a sperm cell last in the female reproductive tract?
Sperm cells can last up to 5days
How can fertilization occur?
Fertilization occurs when intercourse takes place either 4-5 days before ovulation or few hours after ovulation
What is contraception?
Contraception refers to methods of birth control, family planning or prevention of pregnancy. They may be temporal or permanent.
Briefly talk on any 3 short term temporal contraceptive methods
- Rhythm method: this method employs calculative avoidance of intercourse near the time of ovulation. It’s efficiency is low.
- Barrier method: this refers to the use of male condoms or female condoms (cervical cap or diaphragm)
- Chemical method: this involves the use of chemical substance with spermicidal action
- Oral contraceptives: also called birth control pills, they inhibit follicle growth and ovulation, that is, menstrual cycle becomes annovulatory.
Talk about oral contraceptives
There are 3 types of oral contraceptives
1. Estrogen only
2. Progesterone only
3. Combined pills
Talk about long term contraceptives
Long term contraceptives such as implants containing progesterone or intrauterine devices (IUD) having cooper with spermicidal action released slowly into the body are used to prevent fertility for 4-5 years.
Examples of permanent methods for contraception.
Sterilization e.g Tubectomy or vasectomy
What is Tubectomy?
Tubectomy or Tubal ligation refers to the surgical removal or blockage of the fallopian tube.
What is vasectomy?
Vasectomy refers to the surgical process where the vas deferens is cut and the ends ligated, so that sperm cannot enter the ejaculatory duct.
Hence, released semen is devoid of sperm.
What are emergency contraceptives?
Emergency contraceptives are used to prevent pregnancy after unprotected sex.
Emergency contraceptives can be effective within 72-120 hours after sexual intercourse.
Emergency contraceptive pills do not induce abortion.
What are the types of emergency contraceptive pills and their function?
- Ulipristal: prevent/delay ovulation by affecting progesterone effectiveness
- Progestin only: stops/delays ovulation to prevent pregnancy.
- Combined EC pills: contain both estrogen and progesterone, taken ASAP to prevent prevent up to 5 days after unprotected sex
The female reproductive organ is made up of internal & external sex organs collectively called?
Sex accessory organs
What are the internal female sex organs?
- Uterus(houses developing fetus)
- Fallopian tubes
- Ovaries (produces eggs)
What are the external female sex organs?
- Labia majors
- Labia minors
- Clitoris
- Vaginal opening
What are the functions of the ovary?
- The ovary secrets hormones which control development of secondary sexual characteristics beginning at puberty
- The ovary produces eggs via oogenesis
- The ovary produces sex hormones e.g estrogen & progesterone.
- The release of mature oocyte via ovulation
What is Oogenesis?
It occurs in the ovarian cortex, beginning with the process of developing oocytes. Oogonia is transformed into primary oocyte (a process called oocytogenesis), then the primary oocyte develops into an ootid (a process called ootidogenesis). This process is possible via meiosis.
Meiosis 1: primary oocyte will undergo crossing over to shuffle their genes. Meiosis 1 occurs to divide the cell into secondary oocyte. & first bodies degenerate.
Meiosis 2: is halted at metaphase 2, until fertilization. When meiosis 2 is completed post fertilization, ootid & another polar body are created.
Talk about Oestrogen?
Oestrogen is the primary female sex hormone. It is responsible for development & regulation of female reproductive system & secondary sex characteristics.
Like all steroid hormones, estrogen diffuse across cell membrane. Once inside the cell, they bind to activate estrogen receptors which modulate the expressions of many genes.
What are the functions of Oestrogen to different parts of the female sex organ?
- In the ovary, Estrogen stimulates the growth of an egg follicle.
- In the vagina, It stimulates the growth of the vagina and thickening of the vagina walls
- In the vagina, It increases vaginal acidity that reduces bacterial infections.
- It also helps to lubricate the vagina.
- In the fallopian tube, Estrogen is responsible for the contraction that transports the egg & sperm cells.
- In the cervix, Estrogen regulates the flow & thickness of uterine mucous secretions
Talk about Progesterone
Progesterone is an endogenous steroid hormone involved in
1. Menstrual cycle
2. Pregnancy
3. Human embryogenesis
What are the pregnancy hormones?
- Prolactin
- Human Chorionic Gonadotropin
- Human Chorionic Somatomammotropin
What is Menstruation?
Can be defined as the shedding of the superficial layer of the endometrium due to withdrawal of progesterone following luteolysis.
Menstruation occurs as a result of enzymatic auto digestion & ischemic necrosis. It is marked by 3-7 day period of bloody discharge
The first menstruation is called?
Menarche
Explain the menstrual cycle?
Menstrual cycle refers to the monthly rhythmical changes in hormonal secretions and corresponding physical changes. It has an average of 28 days (although it may vary from 21 days to 35 days in some people).
What happens in the follicular phase of the menstrual cycle?
- Follicular maturation
- Spans from day 1-14
- Increases activities of FSH&Estrogen
- Rebuilding of the endometrium
What happens in the ovulatory phase of the menstrual cycle?
- Release of mature ovum(occurs in less than 5 mins)
- Siege in LH level
- Ovulation occurs
What happens in the luteal phase of the menstrual cycle?
- Increased progesterone level
- Formation of corpus luteum
- Increased blood flow to released ovum
- Decreased estrogen level
Talk about the disorders of menstruation
- Amenorrhea: absence of menstruation
- Dysmenorrhea: painful menstruation
- Menorhagia: heavy, prolonged bleeding
- Polymenorrhea: infrequent period of 21 days or less.
- Intermenstrual bleeding
- Hypomenorrhea: uterine bleeding that is regular but decreased in amount.
Explain Menopause
Menopause refers to the permanent cessation of menstruation. This results from loss of follicular activity, the ovaries are no longer able to produce enough estrogen to proliferate the endometrium, thus triggering the end of fertility.
List the symptoms resulting from absence of estrogen in post menopausal women
- Hot flashes
- Atrophy of genitalia & breast
- Osteoporosis
- Hypercholesterolemia
- Irritability, anxiety & fatigue
Talk about growth hormone
Also called somatotropin, secreted by the somatotropes present in acidophilic cells of the anterior pituitary. Somatotropin acts to increase bone length & thickness, regulate metabolism by increasing protein synthesis, promoting anabolism , mobilizing lipids from adipose tissues for gluconeogenesis while increasing storage of glucose as glycogen.
Growth hormone functions through somatomedin, secreted by the liver. Somatomedin is important because even if growth hormone is normal, if somatomedin is absent, dwarfism still occurs.
What are the actions of somatomedin?
- Somatomedin acts on bones and proteins through cyclic AMP.
- It plays a role in fetal growth
- It also forms the hormone-receptor complex which induces intracellular pathways.
What stimulates growth hormone?
Growth hormone is stimulated by (GHRH) Growth hormone Releasing hormone or (GHRP) Growth hormone Releasing Peptides.
It is also stimulated by hypoglycemia, fasting/starvation, exercise, stress, trauma, initial stages of sleep.
What inhibits growth hormone?
Growth hormone is inhibited by (GHIH) Growth Hormone Inhibitory Hormone.
It is also inhibited by hyperglycemia, increased fatty acid in the blood, later stages of sleep.
Hypersecretion of growth hormone causes?
Gigantism or Acromegaly
Hyposecretion of growth hormone causes?
Dwarfism or stunted growth
Briefly talk about Prolactin?
Prolactin is a necessary hormone in milk secretion & even development of mammary glands.
Prolactin is inhibited by Prolactin inhibitory Peptide from the hypothalamus. However from the 5th month of pregnancy, it is no longer inhibited to aid proliferation and preparation for breast feeding
Briefly discuss FSH
FSH meaning Follicle Stimulating Hormone, are released by the basophillic cells of the anterior pituitary, after stimulation from Gonadotropin Releasing Hormone from the hypothalamus. Its receptors are in the gonads(testis,ovaries).
FSH act via cyclic AMP, and it acts to
1. Initiate spermatogenesis, in males
2. It regulates estrogen secretion, in females
How is FSH regulated?
Estrogen inhibits FSH & GnRH(Gonadotropin Releasing Hormone) secretions by negative feedback mechanism
Briefly discuss LH
LH meaning Luteinizing Hormone, are also released by the basophilic cells of the anterior pituitary gland, under the influence of GnRH from the hypothalamus. Its receptors are in the gonads.
What are the functions of LH in males and females
- In males, LH is essential for secretion and release of testosterone from Leydig cells.
- In females, LH causes ovulation, and activates the corpus luteum to secrete progesterone
How is LH regulated?
Testosterone and progesterone inhibit release of LH via negative feedback mechanism
Succinctly discuss ACTH?
ACTH meaning AdrenoCoticotropin Releasing Hormone, is releases by the basophilic cells of the anterior pituitary and it acts to
1. Regulate glucocorticoid secretion
2. ACTH is necessary for structural integrity & secretory activity of the adrenal cortex
In simple terms, ACTH manages the adrenal cortex and this cortex produced Cortisol.
Briefly discuss TSH
TSH meaning Thyrotropin Stimulating Hormone, is also secreted by the basophilic cells of the anterior pituitary. TSH is regulated by TRH(Thyrotropin Releasing Hormone) from the hypothalamus.
TSH is important for synthesis of T3 (Thyroxine) & T4(Tri-iodothyronine).
Explain the synthesis of T3 (Thyroxine) & T4 (Tri-iodothyronine)
Synthesis of T3 & T4 takes place in Thyroglobulin, present in follicular cavity.
Both Iodine & tyrosine are gotten from diet and are essential for the synthesis.
Iodine is absorbed in the blood as iodide and is transported by sodium-iodide symport pump from the blood into the follicular cells, after which it is oxidized into iodine by thyroid peroxidase.
From the follicular cells, iodine is transported into the follicular cavity by Pendrin.
Iodine combines with tyrosine in the follicular cavity in a process called Iodination, catalyzed by the enzyme Iodinase.
Iodination leads to formation of either mono-iodotyrosine(MiT) or Di-iodotyrosine(DiT)
1 MiT + 1DiT = Tri-iodothyronine
2 DiT react to give T4