Mitosis and Meisosis Flashcards
diploid cell
Cell that contains 2 sets of chromosomes - one from each parent
Germ cell
cells that lead to production of gametes - produced by meiosis
Haploid cell
Cell that contains one complete set of chromosomes
Meiosis
Cellular reproduction that forms 4 haploid cells from one diploid cell. Contains 2 cellular divisions that follow only one round of DNA replication - produces germ cells
Mitosis
5 step process by which a cell separates replicated chromosomes before cytokinesis and forms 2 daughter cells from one original cell .
What are the stages of miotosis
Prophase Prometaphase Metaphase Anaphase Telophase
Somatic cell
Any plant or animal cell that isn’t a germ cell, formed by mitosis
Stem cells
Biological cells that can differentiate into other types of cells and divide to produce more of the same type of stem cells. They are always and only found in multicellular organisms
Zygote
Fertilised egg cell
Cytoskeleton
???
Early prophase
cell rounds up into a ball
chromatin begins to condense
nucleolus disappears
centrioles begin to move to opposite poles of cell
microtubules dissolve and reassemble around centrosomes from which they extend
Prometaphase
chromosomes condense and arrange into sister pairs - chromatids
chromosomes begin to move
centrioles begin to move to opposite poles of cell
microtubules have formed the mitotic spindle
proteins attach to the centromeres to form kinetochores
spindle microtubules attach to kinetochores and pull on chromosomes
nuclear envelope disperses
Metaphase
Paired chromatids align along the cell equator by the mitotic spindle
Midline of cell
mitotic plate
Anaphase
Paired chromosomes separate at their kinetochores and move to opposite poles along the microtubules
Telophase
Chromosomes arrive at opposite poles
new nuclear envelopes form around each daughter nucleus
mitotic spindle disperses
chromosomes disperse as their chromatin becomes diffuse
Cytokinesis
Actin ring
cleavage furrow
What holds pairs of homologous chromosomes together?
Synapsis
Synapsis
Early in prophase 1 homologous chromosomes come together to form a synapse, bound by synaptonemal complex and cohesion proteins
crossing over/ crossover
Occurs between homologous chromosomes but not sister chromatids. There is an exchange of genetic material
Primordial germ cells
Earliest recogniseable precursors of gametes 24 days after fertilisation in the endodermal layer of yolk sac
Germ cells
exit from the yolk sac and migrate through dorsal mesentery to primordia of gonads
what is oogenesis
development of an ovum
What is spermatogenesis
development of a mature spermatozoa
Oogenesis
primordial germ cells develop in yolk sac > oogonium (in gonads) > mitosis > oogonium > start meiosis 1 > primary oocytes arrested in prophase 1 (at birth) > 1st meiotic division producing polar body > secondary oocyte arrested in metaphase 2 during ovulation > 2nd meiotic division producing polar body > mature ovum > fertilised egg
Spermatogenesis
Primordial germ cells in yolk sac > spermogonium > mitosis > primary spermatocytes > 1st meiotic divisions > secondary spermatocytes > 2nd meiotic divisions > spermatids > spermatogenesis packaging > spermatozoa
Symptoms of pregnancy
Varicose veins Anaemia Flushed and hot Breast enlargement Pelvic pain swollen ankles morning sickness constipation heartburn breathless urinary infection urinary frequency glucose in urine
What causes pregnancy symptoms
Adaptations in the... respiratory system renal system cardiovascular system metabolism
Positive feedback systems in pregnancy
prolactin secretion in breast feeding
oxytocin secretion in labour
oestrogen secretion by follicles to trigger ovulation
Ovulation
hypothalamus releases Gonadotropin-releasing hormone which acts on anterior pituitary gland to release FSH which stimulates growth and development of follicle. Oestradiol from maturing follicle stimulates release of LH which stimulates ovulation and corpus luteum formation
Luteal phase
corpus luteum releases progesterone which prepares the uterus
corpus luteum not sustained in the absence of fertilisation
Fertilisation
spermatozoa and oocyte fuse and undergo mitosis which forms a blastocyst.
Post-fertilisation
Blastocyst secretes hCG which supports the corpus luteum corpus luteum continues to release progesterone and oestrogen which sustains the uterus.
When is the hCG peak?
between week 2 and week 14
What is hCG?
Human Chorionic Gonadotropin
hCG
glycoprotein hormone, which is rapidly secreted from trophoblast. Used for pregnancy testing and causes morning sickness
What can hCG be a sign of
Pregnancy
ectopic pregnancy
trophoblastic tumours
pineal tumours
Miscarriage
If progesterone fails for any reason the endometrium and developing embryo are shed producing a miscarriage and the corpus luteum dies
What hormones are produced by the placenta?
Progesterone - takes over from corpus luteum by weeks 10-12
Oestrogen
hCG
Human placental lactogen
Where is progesterone synthesised?
Placenta
What affect does progesterone have on uterus?
smooth muscle relaxation preventing fetal expulsion and cervical plug formation which acts as a microbial barrier.
What does progesterone target?
uterus
homeostasis
breast
relaxes other smooth muscle in the body - blood vessels, GI tract, ureters and bronchi
What does progesterone do to homeostasis?
Hyperventilation
weakly stimulates sodium reabsorption and increases water recovery - causing water retention
What does progesterone do to breasts?
stimulates development of lobular tissue but inhibits milk production
what is lobular tissue?
milk producing glands and ducts of the breast
when do progesterone levels fall?
last few days of pregnancy
What does oestrogen affect?
uterus
breasts
what does oestrogen do to the uterus?
myometrial cell growth - for growing fetus, connexin insertion - electrochemical links (gap junctions) between myometrial cells
oxytocin receptor insertion in prep for labour
PGE2 production stimulated which softens the cervix
what does oestrogen do to the breast?
breast duct development
but inhibits milk production
oestrogen production
complex production as placenta is unable to produce the enzyme needed to convert progestogens to androgens so fetal contribution is needed
normal hypothalamic pituitary axis
hypothalamus produces corticotropin releasing hormone which causes the anterior pituitary to produce corticotropin > adrenal cortex produces cortisol
How is oestrogen produced in pregnancy?
Placenta secretes corticotropin releasing hormone > causes anterior pituitary in mother and fetus to secrete corticotropin which acts on the adrenal cortex in fetus and mother to secrete cortisol and DHEA in fetus and just cortisol in mother. DHEA > oestrogen > supports pregnancy
what does cortisol do to fetus?
lung maturation
what does a sudden surge of CRH do?
triggers labour
oestrogen levels over pregnancy
increase over 40 weeks and sharply decline after birth
what does human placental lactogen affect?
mother and fetus
what does human placental lactogen do in the mother?
insuline resistance - decreases glucose utilisation and increases blood glucose
Lipid breakdown - generates free fatty acids
breast development
has similarities with growth hormone
what does human placental lactogen do in fetus?
promotes growth due to more glucose available from mother by insulin resistance
what happens to blood volume in pregnancy?
vascular capacity increased by utero placenta circulation
blood loss expected at delivery
what happens to blood oxygen carrying in pregnancy?
O2 requirements increase - greater maternal and fetal needs
What happens to blood clotting in pregnancy?
haemostasis required when placenta shears off after delivery. In pregnancy there is a drop in anti-thrombin levels and so blood is in a pro-thrombotic state
Anaemia in pregnancy
due to increase in blood plasma there are fewer RBCs for the volume of blood - functional anaemia despite the increase in red blood cell mass
what chemicals are needed more in pregnancy?
Folate
Iron
what happens to the heart in pregnancy?
more oxygen needed and circulation distance increased
increased abdominal mass moves heart upward and out
how is BP calculated
cardiac output x systemic vascular resistance
how is cardiac output calculated
stroke volume x heart rate
what happens to cardiac output in pregnancy
increase in venous return causes increase in stroke volume - starling’s law and due to oestrogen which increases contractility. This increases cardiac output, as does oestrogen by increasing heart rate
what happens to BP in pregnancy?
as cardiac output has increased by 45% systemic vascular resistance has to fall to maintain BP.
How does systemic vascular resistance fall
renal blood blow doubled
large utero-placental bed takes blood
skin blood flow increase by 5 times - helps lose heat - causing flushed and hot feeling
Vasodilation caused by progesterone
pregnancy impact on veins
venous compression due to expanding uterus, impairs venous return causing pooling and distension - varicose veins
how can pregnant women not position themselves?
lying on left side
What happens to the lungs in pregnancy?
oxygen consumption and CO2 production increase and the diaphragm is displaced by abdomen
respiratory changes in pregnancy
tidal volume increase
resp. rate unchanged
airway resistance and functional residual capacity drops. partial pressure of CO2 is lower
what causes respiratory changes in pregnancy?
progesterone
carbon dioxide control in pregnancy
progesterone increases sensitivity of chemoreceptors to CO2 which increases ventilation and drops the pressure of CO2 - breathlessness
What happens in the kidneys in pregnancy?
increased perfusion due to increased plasma volume, decreased reno-vascular resistance and increased cardiac output and decreased plasma oncotic pressure due to dilution
why is there an increase in urine production in pregnancy?
increase in glomerular filtrate rate
greater reabsorption but still more urine produced
glucose in urine as filtered glucose may exceed reabsorption limit
Later in pregnancy what is the main cause of urinary frequency?
Pressure on bladder by enlarging uterus
fluid changes in pregnancy
aldesterone activated to ensure too much sodium isnt lost
osmoregulation changes and so plasma osmolarity dropping doesn’t cause more water loss
results in retention of water and sodium - swollen ankles
all caused by progesterone
metabolism in pregnancy
metabolic rate increases
Changes in GI tract in pregnancy
slower transit - constipation
increased nutrient absorption
oesophageal reflux - heart burn
breast changes
oestrogen - mammary duct development
progesterone - lobular tissue development
these both inhibit prolactin which stimulates milk production
what happens in breasts after delivery
drop in oestrogen and progesterone stops inhibition of prolactin so milk production occurs and oxytocin causes milk ejection
what causes prolactin release
nipple stimulation causes hypothalamus to release prolactin releasing hormone which causes anterior pituitary to secrete prolactin
what does prolactin do
suppresses ovulation and causes breast tissue development in pregnancy and causes milk production after pregnancy
what causes oxytocin release
nipple stimulation and cervix/ vaginal distension cause oxytocin production in hypothalamus and release from posterior pituitary
what does oxytocin do?
uterine contraction and milk ejection - myoepithelial cell contraction
Glands
epithelial tissue derivatives specialised for secretion
secretion
biochemical release from a particular type of cell upon stimulation
endocrine glands
secretions enter bloodstream - ductless glands
exocrine glands
gland with ducts that channels its secretion
hormone
chemical messengers secreted into the blood by endocrine glands in response to an appropriate signal and exerting their effects on target cells that have receptors that bind with the hormone
types of hormones
hydrophilic and lipophilic
what hormones are hydrophilic
peptides and catecholamines
what hormones are lipophilic
steroids and thyroid hormone
peptide hormones
produced by protein synthesis, travel in blood, cannot enter cells, bind to cell surface receptor, trigger event on inside surface of membrane
fast acting
Steroid hormones
produced by modification of cholesterol molecule by enzymes travel in blood bound to plasma proteins enter cells easily intracellular receptor act on DNA to alter cell function slow acting - time for transcription
why is the type of hormone important?
affects administration, peptide hormones cannot be given orally as they will be digested in the stomach
how do peptide hormones work
bind to receptor on outside of cell and cause ATP conversion to cAMP
how do steroid hormones work?
pass through phospholipid bilayer and bind to receptor on gene, causing protein synthesis leading to cell response
role of endocrine system
metabolism, water and electrolyte balance stress response growth and development reproduction RBC production coordination of circulation coordination of digestion
endocrine glands
hypothalamus pituitary thyroid parathyroid adrenal cortex adrenal medulla kidney stomach pancreatic islets duodenum and jejunum ovary testis
pituitary
anterior and posterior lobe
connects to hypothalamus via pituitary stalk
hypothalamus
controls pituitary hormone release
interface between events inside and outside the body and their endocrine response
what hormones are released by hypothalamus?
corticotropin releasing hormone thyrotropin releasing hormone somatostatin gonadotropin releasing hormone growth hormone releasing hormone prolactin releasing hormone prolactin inhibiting factor
anterior pituitary
controls activity of other endocrine glands
involved in ovulation and pregnancy
sperm production
growth
what hormones are released by anterior pituitary gland?
thyroid stimulating hormone adrenocorticotrophic hormones luteinising hormone follicle stimulating hormone growth hormone prolactin
how is the hypothalamus and pituitary linked?
anterior pituitary - blood vessels
posterior pituitary - neurones
posterior pituitary
involved in regulating water balance
uterine contraction
ejection of milk
what hormones are released by posterior pituitary?
ADH
oxytocin
what is the process of hormones of thyroid?
HPT axis
what is the process of hormones of reproduction?
HPG axis
what is the process of hormones of adrenal gland
HPA axis
Testis
releases testosterone
which:
masculinises the reproductive tract and external genitalia
promotes growth and maturation of reproductive system at puberty
spermatogenesis
develops sex drive
secondary sexual characteristics
ovaries
release oestrogen and progesterone which: mature and maintain reproductive system female secondary sexual characteristics ova maturation and release transport of sperm to site of fertilisation preparing uterus for development of embryo and foetus contribute to ability to produce milk
thyroid
controls metabolic rate
increases heart rate
needed for normal growth and development
what hormones does thyroid release?
triiodothyronine (T3)
thyroxine (T4)
parathyroid
calcium metabolism
raises free plasma calcium by mobilising bone stores, reducing urine loss and increasing gut absorption
what hormones does the parathyroid release
PTH
kidney
releases renin if circulating volume or BP is low - sodium is retained and volume restored. releases erythropoietin when hypoxic to increase RBC formation in bone marrow
hormones released by kideny
renin - stimulates aldosterone release from adrenal cortex
erythropoietin
adrenal cortex
metabolic response to stress
body sodium levels
what hormones are released by adrenal cortex?
cortisol
aldosterone
DHEA
adrenal medulla
fight/ flight response
what hormones does the adrenal medulla release
catecholamines
what hormones are involved in digestion and food absorption?
gherlin gastrin secretin and CCK GIP Peptide YY3-36 insulin glucagon somatostatin
what does gherlin do?
stimulates appetite
what does gastrin do?
stimulates HCL production for protein digestion
what does secretin and CCK do?
coordination of digestive functions
what does Peptide YY do?
signals satiety
what does somatostatin do?
inhibits absorption of nutrients
adipose tissue
endocrine gland
what does adipose tissue secrete?
visfatin apelin leptin TNF-alpha adiponectin RBP-4 resistin many causing insulin resistance
Which axis is involved in the formation of mature sperm?
HPG axis
HPG axis
Hypothalamus produces CnRH > pituitary releases FSH and LH > FSH acts on Sertoli cells and LH on Leydig cells
Where are Sertoli cells found?
Seminiferous tubule of testes
Where are Leydig cells found?
Interstitium of testes
What do Sertoli cells do?
in response to FSH they produce Androgen binding protein which causes spermatogenesis
what do Leydig cells do?
Produce testosterone in response to LH.
What does testosterone do?
allows sertoli cells to produce androgen binding protein, which than binds to testosterone and causes spermatogenesis and
peripheral effects
what are the peripheral effects of testosterone?
maintain libido
muscle bone growth
secondary sex characteristics
accessory gland maintenance
Negative feedback of the HGT axis in males
Inhibin is produced by Sertoli cells which reduces FSH production by pituitary which reduces androgen binding protein levels
Testosterone affect on negative feedback of HPG axis
rise in testosterone levels causes reduced production of GnRH by hypothalamus and decreased production of LH and FSH by pituitary
which cells are affected by testosterone
sustentacular cells of seminiferous tubules
Phases of spermatogenesis
spermatocytogenesis
Spermiogenesis
what happens in spermatocytogenesis
germ cell undergoes cell division to form spermatids
What happens in spermiogenesis
maturation and differentiation of spermatids
what are spermatids
immature sperm
what are leydig cells
interstitial cells
where are sertoli cells?
around outside of lumen of testes, surrounded by basement membrane
what is spermiogenesis
remodelling and differentiation into mature spermatozoa
what are the phases of spermiogenesis
golgi
acrosomal
tail
maturation
what happens in the golgi phase
golgi body enzymes form the acrosome
what happens in the acrosomal phase
acrosome condenses around the nuclues which allows it to penetrate the egg and protects the nucleus
what happens in tail phase
centriole elongates to form the tail
what happens in maturation phase
loss of excess cytoplasm to make it aerodynamic
What is spermiation?
process by which mature spermatozoa are released from the protective sertoli cells into the lumen of the seminiferous tubule and the remaining unnecessary cytoplasm and organelles are removed.
The spermatozoa are mature but lack motility - so are sterile . They are transported to the epididymus in testicular fluid secreted by sertoli cells and peristaltic contraction . Sperm travel and stored in vas deferens, this is aided by secretions of the seminal gland, they gain motility
Making spermatozoa fertile
once motile sperm are still not fertile they have to undergo capacitation
Capacitation
A glycoprotein coat covers the acrosome and prevents the sperm fertilising the egg. Capacitation happens due to enzymes fertilisation promoting peptide (produced by prostate gland) and heparin in female reproductive tract which remove the coat and allow sperm to bind to the egg .
FPP
produced in prostate gland as a component of seminal fluid. High levels in MRT prevent capacitation but they drop in the FRT and promotes capacitation
sperm transport into FRT
ejaculate is deposited in the anterior vagina near the cervix . The vagina is open to infection so has high acidity and immunological defence so to reduce the risk of damage to sperm they must travel quickly through the cervical canal. The cervix is only penetrable at certain points of the month - when there is a watery mucus and oestrogen levels are high - 2-3 days per cycle. The cervix has crypts - infoldings of epithelial cells in the endocervical canal which create a reservoir for sperm so they can be released over several hours and chance of fertilisation is increased .
what is in ejaculate?
spermatozoa
seminal fluid
enzymes - protease, seminalplasmin, prostatic enzyme and fibrinolysin
normal semen
more than 1.5ml
pH higher than 7.2
normal sperm
conc. = >15 million/ ml total no. = >39 million per ejaculate total motility = >40% or >32% with progressive motility vitality = >58% live spermatozoa sperm morphology = >4%
Blood testing for fertility
hormone profile - FSH, LH, Testosterone and prolactin
History taking for fertility
libido status, erectile dysfunction, diabetes, retrograde ejaculation, taking drugs that may affect erection
Examine penis and scrotum
size STD symptoms hypospadias urethral meatus - hole may be in wrong place texture scar tissue inflammation ductus deferens blockages
hypogonadism
diminished functional activity of the gonads - testes or ovaries, may result in diminished production of sex hormones
due to testicular disorder or disease involving hypothalamus and pituitary gland
Hypergonadotrophic hypogonadism
issues with testes or ovaries - primary/ peripheral hypogonadism
When there is a problem with testosterone production it causes low levels which sends signals to hypothalamus causing more GnRH to be released and more FSH and LH but testes are damaged so testosterone remains low. Presentation = high FSH, LH and GnRH but low Testosterone
Hypogonadotrophic hypogonadism
low testosterone because there is low gonadotrophin because there is a problem with the hypothalamus
What causes hypogonadotrophic hypogonadism
kallmann syndrome
drugs
alcohol
infectious lesions
What causes high prolactin, and low testosterone, LH and FSH
Hypersecretion of prolactin
caused by pituitary tumours and is drug induced
leads to inhibition of GnRH - reduces LH, FSH and testosterone
causes low libido and erectile dysfunction
what does prolactin do?
inhibits release/ reduces release of GnRH
Follicular phase of menstrual cycle
pre-ovulation
Hypothalamus releases GnRH which causes anterior pituitary to release FSH and LH
FSH causes 15-20 follicles to start developing and this causes the granulosa cells around follicles to secrete oestrogen
Phases of menstrual cycle
follicular phase
luteal phase
14 days each
which phase is always 14 days in the menstrual cycle
luteal phase
What does FSH do?
stimulates development of follicles
What does LH do?
Causes ovulation
What does oestrogen do?
promotes female secondary characteristics
develops breast tissue, vulva, vagina and uterus and endometrium
stimulates blood vessels in uterus
causes mucus in cervix to become thinner to allow penetration of sperm
Causes negative feedback
Oestrogen…
causes negative feedback on hypothalamus and anterior pituitary. Rise in oestrogen suppresses release of FSH and LH
What happens just before ovulation?
dip in oestrogen as follicles get ready to release egg
rise in LH which causes 1 follicle to reach surface of ovary and release the ovum at day 14
luteal phase
follicle that released ovum collapses and becomes corpus luteum and releases progesterone
when does ovulation happen?
day 14
what does progesterone do?
steroid sex hormone
thickens and maintains endometrium
thickens cervical mucus
increase body temperature
corpus luteum
secretes progesterone and oestrogen
what happens if egg is fertilised
embryo secretes hCG
maintains corpus luteum
what happens if egg is not fertilised
corpus luteum degenerates and no long produces progesterone and oestrogen. this reduces negative feedback causing FSH and LH to be secreted
drop in oestrogen and progesterone causes endometrium to break down causing menstruation
when does menstruation start?
day 1
menstruation
where superficial and middle layers of endometrium separate from basal layer and are broken down in uterus and released through cervix and vagina
lasting 1-8 days
development of ovarian follicles
primordial follicle > primary follicle > secondary follicle > graafian/ mature follicle > ovulation
what does oestrogen do in negative feedback
as oestrogen is produced it causes reduction of FSH production
basal level of LH
mature follicle
produces large amounts of oestrogen which causes positive feedback and increases LH production via GnRH - causes LH surge. FSH is produced but inhibin prevents surge of FSH
What does the LH surge do?
restarts meiosis
oocyte undergoes another meiotic division
activates enzymes that break down wall to rupture follicle
oestrogen production stops as follicle dies
luteal phase
progesterone inhibits FSH and LH to stop further follicle development and ovulation
prepares uterus for pregnancy
oestrogen should cause positive feedback but is overridden by progesterone negative feedback
if fertilisation does not occur
corpus luteum degenerates spontaneously progesterone fails uterus loses its endocrine support menstruation FSH and LH gets to work again on follicles
what are the 2 layers of the uterine wall
myometrium
endometrium
what does oestrogen do to the uterus
promotes growth of endometrium and myometrium
promotes formation of progesterone receptors
what does progesterone do to the uterus?
acts on oestrogen-primed endometrium
loosens and softens connective tissue - making implantation easier
promotes secretion of nutrients
quietens uterine activity
uterine loss
no occupants so no hCG, so corpus luteum degenerates
progesterone and oestrogen support lost
uterine prostaglandins cause vasoconstriction and tissue death
blood and endometrial debris loss through vagina
menstrual disorders
dysmeorrhea
mennorrhagia
amenorrhea
oligomenorrhea
what is dysmenorrhea?
painful periods
what is Menorrhagia?
heavy or prolonged periods
What is amenorrhea?
absence of periods
what is oligomenorrhea
light periods
how does the combined pill work?
low dose of oestrogen = reduces FSH from ant. pituitary, reduces development of follicle and no ovulation
Progestrogen = makes cervical mucus sperm-unfriendly
decreases LH from ant. pituitary and GnRH from hypothalamus
reduces motility of fallopian tube
what makes up the combined pill
progestogen
low dose of oestrogen
Progestogen only pill
low dose of progestogen taken continuously
makes cervical mucus inhospitable to sperm
hinders implantation - effect on endometrium and motility and secretions of fallopian tubes
menstruation - often ceases initially but returns long-term
causes breakthrough bleeding and irregular menses
