test 3 (sex cells and shit) Flashcards
what is mitosis?
- cell division
- for growth and repair
- in somatic cells
- a continuous process
what are the phases of cell division?
- G1 (first growth phase) new proteins produced, grows and carries out normal tasks
- S phase (synthesis phase), DNA duplicates
- G2 (second growth phase), preparation for cell division
- M phase (mitotic phase), cell divides into 2 daughter cells
what is interphase?
-G1-S phase
dna forms copies of itself during the S phase
what is prophase?
- 2 pairs of centrioles become visible early on
- centrioles move to piles
- centrioles begin to produce spindle (microtubules)
- nuclear membrane breaks down
- chromatin tightly coils and chromosomes become visible
- chromosomes are made of two chromatids joined at centromere
what is metaphase?
- chromosomes line up down equator of cell
- centromere attached to a spindle fibre
what is anaphase?
- chromosomes seperate at centromere
- chromatids pulled by spindle fibres to poles of cell
- move away from equator to poles
what is telophase?
- chromosomes form tight groups at each pole
- nuclear membrane forms
- nucleolus appears
- spindle fibres disappear
- the cell is pinched into two daughter cells
what is cytokinesis?
- division of the cytoplasm
- furrow develops between the two nuclei
- furrow deepens and cuts cytoplasm in half, results in two daughter cells
how is meiosis different to mitosis?
- parent cell divides twice
- four daughter cells are produced in meiosis (2 in mitosis)
- chromosome number is haploid (diploid crops divide to become haploid cells)
- the daughter cells are not genetically identical
- only occurs in sperm and ova
difference in anaphase 1 (meiosis + mitosis)
- in mitosis, the centromere divide so that each chromatid becomes a chromosome
- in meiosis, the chromatids are not split apart, instead the whole chromosome moves
interphase 2
- there is no interphase 2 in meiosis
- dan does not double in preparation for the second division
what is prophase 2?
- chromosomes condense and become visible
- spindle fibres start to form
what is metaphase 2?
-chromosomes line up down equator and spindle fibres attach
what is anaphase 2?
-chromosomes are split at the centromere and sister chromatids are pulled to opposite poles
what is telophase 2?
- spindles disappear
- nuclear membrane forms
- cytokinesis - cytoplasm is split
- 4 non-identical daughter haploid cells
what is spermatogenesis?
- all stages occur in testes continuously after puberty
- spermatogonia begin dividing by mitosis
- daughter cells grow and become primary spermatocytes
- final stage occurs when the spermatic matures into spermatozoa
- takes 72 days
what is sperm?
- microscopic
- tail is used to propel cell forwards
- the head contains nuclear material and enzymes
- the middle has mitochondria
what is oogenesis?
- millions of egg mother cells (oogonia) develop before birth in the ovaries
- these cells divide by mitosis and will become ova
- oogonia grow into primary oocytes
- at birth, ovum is still in prophase 1
- 1 per month matures metaphase 2
- meiosis is complete if fertilised
- produces 1 viable ovum and up to 3 polar bodies
gonads:
- two testes
- site of spermatogenesis
- works best at 35°C
- testes can contract/ expand depending on weather
testis:
- lobules filled with tiny tubes
- tubules lined with cells that produce sperm
- interstitial cells lay in between the seminiferous tubules— produce testosterone
- larger tubes join to form ducts
- ducts lead out of testes via epididymus —> vas deferens
epidiymus:
-sperm stored here for up to a month
vas deferens:
-carries speed away from testes and connects to urethra
semen:
-require:
a water medium to swim
a nourishing environment that provides sugars they need to fuel their journey
protection against acidic conditions of vagina
ovaries:
- made up of a connective tissue (stroma- made up of a layer of germ cells)
- endocrine glands secrete oestrogen and progesterone
the ovarian cycle:
- development of follicles and corpus luteum
- at birth 400,000 immature eggs- only 400 mature
- these eggs rest until puberty encased by primary follicles (single cell layer)
- length 28 days
ovarian cycle: secondary follicle
- cells surrounding the egg enlarge, divide and secrete —> a fluid filled space around egg (now secondary follicle)
- more fluid accumulated within follicle —> enlarges and moves to surface of ovary
- now the mature follicle (14 days)
how is the corpus luteum formed?
- mature follicle bursts—> egg is swept down fallopian tube via cilia
- ovulation occurs (release of egg)
- the ruptured mature follicle collapses and forms a blood clot —> absorbed by follicle cells and enlarged to form corpus luteum
corpus albican:
- if no fertilisation, corpus luteum reaches max development 8-10 days
- then degrades and becomes corpus albican
menstrual cycle: (5 steps)
- menstruation: 1-4 days —> uterine bleeding, shedding of endometrium
- pre-ovulation: 5-12 days —> endometrial repair begins; development of ovarian follicle; uterine lining thickens
- ovulation: 13-15 days —> rupture of nature follicle, releasing egg
- secretion: 16-20 days—> secretion of mucus by endometrium glands, cervix and uterine tubes, movement and breakdown of unfertilised egg, development of corpus luteum
- premenstruation: 21-28 days —> degeneration of corpus luteum, deteriorating of endometrium
hormone regulation- endocrine glands
- secrete hormones into extracellular fluid
- the secretion enters the blood transport system via capillaries
hormone regulation : pituitary gland
- secrete hormones that stimulate reproductive system
- secretes gonadatrophins
follicle stimulating hormone FSH
-in females, stimulates the development and maturation of the follicle
lutenising hormone LH
- promotes final maturation, ovulation and formation of corpus luteum
- during development, the follicle secretes oestrogen —> FSH reduces as oestrogen increases
corpus luteum:
- secretes progesterone + oestrogen
- as progesterone increase, LH decreases
- maintained by human chorionic gonadatropin (HCG)secreted by placenta
- once placenta starts to secrete progesterone and oestrogen, (3 months into pregnancy) corpus luteum is no longer needed and starts to degenerate
progesterone:
- maintains endometrium
- develops and maintains placenta
- develops milk secreting glands in breasts
hormone regulation in males: pituitary gland
secretes gonadotropin
hormone regulation in males: FSH
stimulates epithelial tissue of seminiferous tubules to produce sperm
hormone regulation in males: LH
stimulates cells in testes to secrete testosterone
hormone regulation in males: testosterone
important for speed maturation and mate reproductive organ maintenance
other hormones secretes from the pituitary gland:
- prolactin (lactogenic hormone)-> production of milk
- oxytocin -> stimulates the concentration of the uterus and promotes contraction of muscle cells in the breasts
fertilisation:
- ovum is surrounded by corona radiata
- sperm contain and enzyme in the acrosome capable of breaking down the corona radiata
- sperm enters ovum, tail is absorbed and head moves thorough cytoplasm in form of male pronucleus
- this mutates the completion of meiosis II and the nucleus of ovum becomes a female pronucleus
- the 2 pronucleus fuse and form a zygote
development of embryo: amnion/amniotic fluid
amnion -surrounds embryo -secretes amniotic fluid into the cavity it forms -expands as the embryo grows -ruptures just before birth (water) amniotic fluid -shock absorber -maintains temperature -allows embryo to move freely
development of embryo: chorion
- forked from outer blastocyst
- becomes placenta
- amnion fuses with chorion as it grows
- chorionic villi protrude into endometrium and allow grander of nutrients from maternal to foetal blood
development of the placenta
- development from chorion- fully developed by 3 months has 5 functions
- develops as blastocyst implants
- contains blood vessels
- pools of maternal blood surround villi
the umbilical cord:
- 2 arteries (carry blood to chorionic villi)
- 1 vein (carries blood from placenta to foetus
changes for pregnant mother:
- enlargement of breasts (hormones for milk-secreting tissue development)
- increase in heart and blood volume (40%)
- extra blood flow (placenta, kidneys)
- increased urination
- emotional changes (hormonal)
- weight gain
- hormone changes promote energy to covert to fat
- water retention
how to maintain a healthy pregnancy?
- increase diet by 850kj
- increase calcium, iron and folic acid
- regular exercise
disruptions to normal foetal development:
- genetics, mutations or environmental factors
- chemicals and drugs that cause physical defects
- maternal diet (lack of folate can cause spina bifida)
how to diagnose foetal health:
- ultrasounds
- fetoscopy (telescope size of a needle through uterine wall, foetal blood sampling)
- chorionic villus sampling for genetic disorders (9-19 weeks)
- electrocardiography (heart monitoring)
labour preparations:
changes in hormones prepare the body for labour and child birth
- pelvis ligaments soften
- sensitivity in uterus increases
- strengthened contractions of uterine muscles
- foetus positions head in mothers pelvis
- cervix softens, shortens and starts to open
the first stage of labour:
- contractions come in waves from top of uterus to cervix (like peristalsis) every 30 minutes
- with each contraction, muscle fibres of the uterus shorten and pull on the cervix
- this shortens cervix until it no longer protrudes into the vagina, begins to open
- dialation allows for foetus to move deeper into pelvis
- cervix fully dialated at 10cm
the second stage of labour:
- begins with breaking of waters
- lasts 20mins-2 hours
- contraction of the uterus and abdominal muscles push the foetus through the vagina
- babies head turns towards mothers back
- eventually head stretches the vagina and perineum
- birth
third stage of labour:
- after birth
- baby begins to breath
- baby is connected to placenta
- amnion, chorion and placenta still in uterus
- umbilical cord is cut
- baby covered in vernix (a waxy protective layer that washes off)
- uterus contracts and pushes out placenta and other membranes
- placental blood vessels constrict
- uterus contractions squeeze uterine blood vessels shut, blood clot forms
changes in the baby at birth:
- infant becomes self supporting
- lungs don’t function before birth- receives oxygen from placenta
- alimentary canal doesn’t function
- circulatory changes need to occur
foetal circulation:
- foetal blood is carried to and from placenta by blood vessels in umbilical coed
- some blood (returning to foetus) flows through liver into inferior vena cava
- other blood bypassed liver via ductus venosus to inferior vena cava
foetal circulation: blood returning to foetus enters right atrium through:
1) right ventricle to lungs: considerable resistance due to collapsed lungs
2) right ventricle to ductus arteriosus to aorta - ductus arteriosus is a kung bypass to pulmonary artery to aorta
3) right atrium to left atrium through foremen ovale - foremen ovale is an opening between the two chambers
circulation after birth:
- lungs and liver must become fully functional
- slap on bum initiates first breath or clamping umbilical cord
- flap of foremen ovale is forced against wall of atrium by increased blood pressure, closing the opening (hole in heart is caused by failure to close)
- ductus arteriosus is left as fibrous tissue
- ductus venosus is constricted and closes
changes to mother after birth:
- puerperium (8 weeks)- mother reproductive organs slowly return
- uterus begins to contract
- discharge from shrinking uterus (breaking down of tissue)
- blood volume decreased
- slow pulse and body temperature
- emotional changes
- return of menstruation can be delayed up to 6 months (breastfeeding) or 10 weeks (not breastfeeding)
milk production:
- 16-25 loves
- loves divided into lobules
- lobules made up of alveoli
- loves and lobules surrounded by fatty connective tissue
- lobules ducts opens into spaces which act as reservoirs for milk
lactation:
- initiation and maintenance of milk secretion
- increases hormones during pregnancy causes changes in breast
- loves become more complex
- colostrum is the first secretion (watery + yellow, contains little to no fat, high antibody content that is absorbed through infants intestine)
milk let down reflex:
- automatic response on suckling
1) nerves in nipples stimulated- message sent to brain
2) brain instructs pituitary gland to release oxytocin
3) oxytocin triggers contraction of small muscles around lobules- milk is then ejected into ducts
4) suckling infant can then draw milk through the nipple
puerperium:
reproductive organs return to non- pregnant start- takes 8 weeks
