Week 12 Science and Scholarship: Reproduction Flashcards
list the functions of the male reproductive system
sperm cell production
sperm cell transfer
sex hormone production
Describe sperm cell production as a function of the male reproductive system
spermatogenesis in the seminiferous tubes of the testes
describe sperm cell transfer as a function of the male reproductive system
sperm transport through the vas deferens and urethra during ejaculation
Describe sex hormone production as a function of the male reproductive system
testosterone secretion by leydig cells in the testes
what are primary vs secondary sex organs
-Primary sex organs are the gonads; produce gametes and sex hormones; includes testes which produce sperm and androgens
-secondary sex organs are essential for caring and transporting sperm cells, include ducts (eg epididymites) which transport sperm, and accessory sex glands (eg prostate) which sustain sperm, and the penis which transfers sperm
what are secondary sex characteristics
features that are not essential for the reproductive process, but are generally considered social attractants eg body physique, hair and voice pitch or fat to breasts/abdomen and hips
name the male secondary sex characteristics
libido
growth of larynx and deeper voice
facial/body hair
developing muscle mass
external genitalia development
function of the testes
male reproductive organs that are responsible for producing sperm cells and testosterone (hormone)
describe scrotum
pouch of skin that houses and protects the testes in the male reproductive system
describe epididymis
a coiled tube located on outer posterior of each testicle, where sperm cells mature and are stored, transports sperm from testes to vas deferens
describe vas deferens
long fibromuscular tube that transport mature sperm cells from the epididymis to ejaculatory duct
describe ejaculatory ducts
short ducts formed by union of vas deferens and seminal vesicles, through which sperm and seminal fluid pass during ejaculation
describe seminal vesicle
sac-like structure that secrete a fluid (60-70% of volume of semen) rich in nutrients and fructose,
describe prostate gland
walnut-sized gland located below bladder that produces milky fluid containing enzymes, added to semen during ejaculation (contributes 20-30% of semen volume)
describe urethra
tube serving as a common passageway for both semen and urine. running through the penis (base to tip) and allowing elimination of waste and release of sperm
describe bulbourethral gland
aka Cowper’s gland, peas sized and paired,
-secretes a clear fluid that lubricates
-neutralises acidity of urethra prior to ejaculation by releasing alkaline mucous
describe penis
male external sex organ, responsible for transferring sperm into female reproductive system in sexual intercourse
name the components of male reproductive system
testes
scrotum
vas deferens
prostate gland
penis
epididymis
seminal vesicles
ejaculatory ducts
urethra
bulbourethral gland
structure of scrotum
-layer of smooth muscle (dartos)
-two skeletal cremaster muscles that descend from the abdomen and cover each teste, like a muscular net
-rich blood and nerve supply
function of scrotum
-to support and protect the testes
-to help regulate temperature of testes (35 degrees)
optimal temperature of testes
35 degrees ( 2 degree below normal)
why do testes require a temperature of 35 degrees
-enables optimal sperm production and testicular function
-ensures normal metabolism
-decreases risk of testicular cancer
name the mechanisms to regulate temperature of testes
-external location
-cremaster muscle
-dartos muscle
-counter-current heat exchange
how does external location regulate taste temperature
testes are located externally, away from warm pelvic cavity
how does cremaster muscle regulate testes temperature
-contracts to lift testes closer to pelvis (increasing temp)
-relaxes to drop testes away from pelvis (decreasing temp)
how does dartos muscle regulate testes temperature
-contracts (wrinkles) to reduce surface area for less heat loss
-relaxes (un-wrinkles) to increase surface area for more heat loss
how does counter-current heat exchange regulate testes temperature
-As the warm arterial blood descends into the scrotum, it passes through the pampiniform plexus.
-The cooler venous blood in the plexus absorbs heat from the arterial blood via conduction.
describe structure of testes
-elliptical
-divided into 300-400 compartments (lobules)
-each lobule contains a long tube (seminiferous tubule) which sperm are produced
what cells are found within the seminiferous tubules
spermatogenic cells and Sertoli cells
function of spermatogenic cells
evolve into sperm cells via spermiogenesis (mitosis then meiosis)
identify function of Sertoli cells
-support
-nutrient provision
-hromone secretion
-blood testis barrier
what structures are found between seminiferous tubules
leydig cells and blood vessels
function of leydig cells
produce androgens eg testosterone
function of blood vessels (interstitial)
exit pathway for androgens
define spermatogenesis
process by which sperm cells are formed
list the events of spermatogenesis
mitosis
meiosis I
meiosis II
maturation
define spermatogonia
undifferentiated male germ cells located in testes that are responsible for production of sperm cells via spermatogenesis
(2n)
define primary spermatocyte
specialised diploid cell that is formed from spermatogonia and undergoes meiosis I to produce two haploid secondary spermatocytes
(2n)
define secondary spermatocyte
haploid cells resulting from meiosis I division of primary spermatocytes which further undergo meiosis II to produce spermatids
(n)
define spermatid
immature haploid cells derived from secondary spermatocytes that undergo a series of morphological changes; form a tail, to eventually develop into mature sperm cells
(n)
define sperm cell
mature male reproductive cells produced through spermatogenesis, characterised by their elongated shape, a head containing genetic material and tail that facilitates movement (fertilisation)
(n)
describe the lineage of cells to make a sperm cell
spermatogonia
primary spermatocyte
secondary spermatocyte
spermatid
sperm cell
whats the difference between spermatogenesis and spermiogenesis
-spermatogenesis is the overall process by which sperm cells form
-spermiogenesis is the final stage of spermatogenesis where:
-acrosome (digestive enzyme)
-flagellum
-condensation of nucleus
-shedding excess cytoplasm
ALL develop
how do Sertoli cells provide ‘support’
physical support and protection for developing sperm cells within the SN tubules
how do Sertoli cells provide ‘nutrient provision’
provide nutrient and metabolic support to developing sperm cells, enduring proper growth and maturation
how do Sertoli cells provide ‘hormone secretion’
secrete hormones such as inhibin, which plays a role in slowing spermatogenesis
how do Sertoli cells play a role in ‘blood testis barrier’
separate sperm from bloodstream, preventing autoimmune response
where are Sertoli cells found
within SN tubules
name the major parts of sperm
acrosome
flagellum
axial filament
mid-piece
head
tail
end piece
function of acrosome of sperm
contains enzymes necessary for penetrating and fertilising the egg during fertilisation
function of flagellum of sperm
enables motility an propels sperm toward egg during fertilisation
function of axial filament of sperm
provides structural support and enables movement
function of head of sperm
essential for delivering genetic material to egg in fertilisation
function of mid piece of sperm
providing energy needed for sperms movement and mobility
function of tail of sperm
propels sperm forward
function of end piece of sperm
aids in propulsion and movement of sperm towards egg
identify each segment of male duct system
epididymis
vas deferens
ejaculatory duct
urethra
seminiferous tubules
reste testis
efferent ducts
function of seminiferous tubules
site of sperm and hormone production in testes
function of reste testis
networks of tubules that carry sperm from testes to efferent ducts
function of efferent ducts
connects reste testis to epididymis
list the changes that occur in sperm cells while in epididymis
-monitor and adjusting fluid composition
-recycling debris and damaged sperm
-protection of sperm in a conducive environment
-functional maturation (enable motility)
How does functional maturation occur in the epididymis
-variety of proteins that bind to sperm provide stability and protection and trigger flagellum movement
-initiated by androgens
list the constituents of semens
sperm cells (4%)
bulbourethral gland fluid (<1%)
seminal vesicle fluid (65%)
prostate gland fluid (30%)
name the three segments of the penis
root
body
glans
structure of the root of the penis
located at the base of the penis
-inside the body and not visible
structure of the body of the penis
-elongated component that is composed of three cylindrical columns of erectile tissue
-two large corpora cavernosa (on sides of penis)
-single corpus spongiosum on underside of penis that surrounds urethra
Describe the processes of orgasm in relation to erectile tissue
-sexual stimulation
-parasympathetic neuron’s release nitric oxide, this causes dilation of the arteries supplying the penis, thereby increasing blood flow to penis
-increasing pressure of arterial blood entering vascular spaces of erectile tissue compresses the veins of the penis, reducing flow of venous blood away from the penis
-follwoing orgasm sympathetic nerves contract the central artery of the penis and contract smooth muscle around the erectile tissues, which expels blood away from penis
describe the function of the corpus cavernosa
responsible for the rigidity of the penis during erection
describe the function of the corpus spongiosum
-protect the urethra
-less significant contributor to erection
where is testosterone produced
leydig cells in the testes
what are the functions of testosterone
-spermatogenesis
-sex drive
-secondary sex characteristics
how is testosterones function linked to spermatogenesis
testosterone initiates and maintains spermatogenesis; preventing infertility due to low testosterone
how does testosterone contribute to sex drive
maintains male sex drive (libido) so that reproduction and sexual desire are produced
how does testosterone contribute to secondary sex characteristics
-forms secondary sex characteristics, to increase attractive appeal and generate ‘male’ characteristic features
Describe the hormonal regulation of testosterone and sperm development
- hypothalamus initiates spermatogenesis by secreting GnRH, which stimulates the anterior pituitary gland to secrete FSH and LH
2.LH stimulates leydig cells to secrete testosterone, FHS stimulates Sertoli cells to secrete androgen-binding protein (ABP), ABP binds to testosterone, which allows it to become more concentrated in the SN tubules and maintains high testosterone levels
3.Increased levels of testosterone initiate spermatogenesis, this also has negative feedback on GnRH
4.Sertoli cells respond to rising sperm levels by secreting inhibin, this inhibits FSH secretion from the anterior pituitary gland thereby having negative feedback
5.Ciruclating testosterone stimulates sex drive (libido) and development of secondary sex characteristics
List the functions of the female reproductive system
oocyte production
hormone production
sperm reception
pregnancy/birth
describe oocyte production as a function of female reproductive system
production of oocytes (eggs) in ovaries (these are female gametes)
describe hormone production as a function of female reproductive system
-production of female sex hormones, including oestrogen and progesterone
-essential to normal function of reproductive system, and reproductive behaviour
describe sperm reception as a function of female reproductive system
-reception of spermatozoa from the male;
-includes structures that receive sperm and transport sperm to site of fertilisation
describe pregnancy/birth as a function of female reproductive system
-development and nourishment of a new individual, nurtures in uterus until birth
-provides nourishment (milk) after birth
what is the function of primary sex organ in females
the gonads are ovaries (produce oocytes and female sex hormones-progesterone and oestrogen)
what are secondary sex organs (female system)
-structures essential to: fertilisation of an oocyte, implantation of a fertilised oocyte; development of individual; parturition (childbirth)
-eg uterine tubules, uterus, vagina and mammary glands
list the structures that make up female reproductive system
ovaries
fallopian tubes
uterus
cervix
vagina
vulva
mammary glands
function of fallopian tubes
-site of fertilisation (ampulla)
-site of sperm maturation (isthmus)
function of uterus
-mechanical protection for embryo
-nutritional support for embryo
-waste removal for embryo
-contracts during birth
describe cervix
-lower part of uterus that connects to vagina
-passageway for sperm and plays role in childbirth
list functions of vagina
menstrual fluid
intercourse
childbirth
what is vulva
-external genitalia
-includes labia mojora, labia minora, clitoris and vaginal opening
function of mammary glands
-glands responsible for producing and secreting milk to nourish newborns after childbirth
Describe position of ovaries
-upper pelvic cavity
-either lateral side of uterus
structure of ovaries
-two ligaments (suspensory and ovarian ligament) support position of ovaries
-ovoid organs, nodular consistency
-outer cortex
-inner medulla
describe cortex (ovary)
-outer region
-contains oocytes and follicular cells that aggregate to from follicles
-site of folliculogenesis and oogenesis
-made of dense CT
describe medulla (ovary)
-inner central region
-contains blood vessels and nerves, this enables follicular hormones (oestrogen) to exit ovary and enter systemic circulation
-made of loose CT
define ovarian cycle
a series of hormonal and physiological changes that occur in the ovaries to prepare for the possibility of fertilization and pregnancy.
name the two processes in ovarian cycle
oogenesis and folliculogenesis
Describe folliculogenesis
-the development of the follicle; the follicle contains both oocytes and support (follicle) cells
-begins before birth
-as oocytes mature more follicular cells surround oocytes; primordial follicles develop into primary, secondary and tertiary follicles
oogenesis vs folliculogenesis
oogenesis is strictly the formation of oocytes (equivalent to spermatogenesis) whereas folliculogenesis is the development of the entire follicle
how does the corpus luteum form
-post follciulogeneis, the oocyte enters uterine tube, most of the follicle remains in the ovary
-the ruptured follicle collapses in on itself, forming a new structure called the corpus luteum
unique function of corpus luteum
unlike the primordial,primary,secondary and tertiary follicles that can secrete oestrogen, only the corpus luteum can produce and secrete progesterone
what are primordial follicles
contains a primary oocyte and single layer of flat follicle cells
what are primary follicles
contains primary oocyte and 1-2 layers of cuboidal follicle cells
what are secondary follicles
contains enlarged oocyte and additional layers of follicle cells, fluid-filled spaces develop between follicle cells
whats a tertiary follicle
-follicle contains single, large fluid-filled space (antrum)
-oocyte is surrounded by specialised follicular cells (granuloma cells)
-ovulation begins (release of oocyte)
whats the corpus albicans
-if fertilisation doesn’t occur, the corpus luteum degrades into the corpus albicans
-composed of scar tissue
-lifespan of 10 days
list the cell lineage that eventually produces oocyte
-primordial germ cells
-oogonium
-primary oocyte
-secondary oocyte
-oocyte
whats an oogonium
-diploid cell that arises before birth
-divides continuously in an embryo, produces several million iterations of itself
-this occurs for three months
-2n
whats a primary oocyte
-oogonium divides to form primary oocytes
-these cells undergo folliculogenesis
-these cells are present at birth
-2n
whats a secondary oocyte
-results from meiosis I of primary oocyte
-can’t be produced until puberty occurs
-(n)
whats a polar body
-waste product
-collects genetic material from meiotic division of primary oocytes
-enables diploid number to be restored
name the segments of the uterine tubule
three segments: infundibulum, ampulla and isthmus
structure of uterine tubule
-hollow, muscular tubes
-3 segments
-walls are composed of ciliated columnar epithelium with scattered mucous-secreting cells
name the regions of the uterus
fundus (superior)
body (central)
cervix (inferior)
name the uterus wall layers
endometrium
myometrium
perimetrium
structure of uterus
-pear size and shaped
-three regions
-wall has three layers
location of uterus
-at floor of pelvic cavity
-anterior to rectum and posterosuperior to urinary bladder
other names for uterine tubules
-aka fallopian tubes or oviducts
structure of endometrium
-innermost layer
-contains epithelium and CT gland
-divided into two structural layers
structure of myometrium
thick layer of smooth muscle (contracts)
structure of perimetrium
external layer
-composed of epithelium
Describe how an ovum is moved through a uterine tubule to the uterus
-ovum is released into peritoneal cavity
-fimbirae (finger like projections) at distal end of uterine tubules create gentle movements that help sweep ovum into tube
-cillia (small hair like projections) that line inner surface of uterine tubule, play a crucial role in moving ovum
-cilliary movements create a wave like motion
-smooth muscles in the myometrium aid ovum movement (peristalsis)
-this whole process tales 3-4 days (ovum is ready for fertilisation)
structure of vagina
-tubular canal that extends from exterior of the body to uterine cervix
-internal wall is stratified squamous (protective)
-beneath this is thin CT (lubricates)
-beneath this is which smooth muscle
-contains bacteria that maintain acidic environment and restrict growth of pathogenic bacteria, yeast and other microorganisms
Describe ‘menstrual fluid’ as a function of the vagina
vagina serves as a passageway fro the elimination of menstrual fluids
Describe ‘intercourse’ as a function of the vagina
receives the penis during sexual intercourse,
-holds sperm prior to passage into uterus
Describe ‘childbirth’ as a function of vagina
forms the inferior portion of birth canal through which the foetus passes during delivery
identify structures of the external female genitalia
vestibule
labia minora
clitoris
prepuce
labia majora
bartholin’s gland
describe vestibule
space into which vagina and urethra open
describe labia minora
small, thin folds of skin that border vestibule
describe clitoris
-small, rounded tissue projection (y shaped)
-contains two erectile structures (2x corpus cavernosa)
-glans clitoris (lots of nerve fibres)
describe prepuce
-extensions of labia minora
-encircles clitoris
describe labia majora
prominent skin folds that encircle and conceal the labia minora
function of bartholin’s gland
secret lubricating mucous into vestibule
how long is the female reproductive cycle
28-40 days
name the phases of the female reproductive cycle
menstrual
pre-ovulatory
ovulation
post ovulatory
Describe the menstrual phase of female reproductive system in ovaries and in uterus
in ovaries: ovarian follicles grow/enlarge
in uterus: stratum functionalis layer of endometrium is degenerated and expelled (menstruation)
Describe the pre-ovulatory phase of female reproductive system in ovaries and in uterus
in ovaries:
-follicles grown and secrete oestrogen
-one follicle dominates and becomes a tertiary follicle
in uterus:
-oestrogen from ovarian follicles stimulates repair and growth of stratum functionalis in endometrium
Describe the ovulatory phase of female reproductive system in ovaries and in uterus
in ovaries:
-tertiary follicle ruptures
-secondary oocyte is released into uterine tubule
in uterus
-stratus functionalism continue growing
Describe the post-ovulatory phase of female reproductive system in ovaries and in uterus
in ovaries:
-remaining follicle becomes corpus luteum
-secretes and oestrogen and progesterone
-luteum can degenerate into albicans
in uterus:
-oestrogen and progesterone from corpus luteum activate uterine glands to secrete mucus
Describe the structural changes that occur in the endometrium during menstrual phase and how these changes are controlled by hormones
-low levels of progesterone and oestrogen trigger:
-shedding of the functional layer of the endometrium (bleeding)
-endometrium becomes thin and contains mostly blood vessels and stromal cells
Describe the structural changes that occur in the endometrium during proliferative phase and how these changes are controlled by hormones
-oestrogen levels rise and oestrogen promotes proliferation of endometrial glandular cells, blood vessel and stromal cells
-this causes thick and glandular endometrium swell as a rich blood supply an
Describe the structural changes that occur in the endometrium during secretory phase and how these changes are controlled by hormones
-after ovulation, progesterone levels increase due to corpus luteus formation
-this promotes development of endometrial glands, increasing their secretory activity
-prepares endometrium for possible implantation of a zygote
Outline the role of GnRH in regulating female reproductive cycle/functions
1.GnRH is secreted by hypothalamus
2.GnRH stimulates FSH and LH release by anterior pituitary
3.FSH stimulates follicles to grow and mature, which secrete oestrogen
4.oestrogen thickens stratum functionalis
5.LH surge triggers ovulation and formation of corpus luteum
6.Corpus luteum secretes oestrogen and PROGESTERONE , which prepares uterus for implantation for a fertilised oocyte
-Progesterone binds to endometrial glands and starts making mucus.
-Mucus is made as it is glycogen rich, and glycogen is an energy source for a fertilised egg.
7.If no implantation, corpus luteum degenerates into corpus albicans which triggers menstruation (bleeding)
describe why millions of sperm are required in an ejaculate
-acidity: acidic ‘attack’ of sperm in vaginal environment
-viscosity:entrapment of sperm within the viscous cervical mucosa
Describe the changes that occur in spermatozoon from ejaculation to fertilisation
*acidity in vagina: vaginal environment is quite acidic hence millions of sperm are overcome and die
*mucous in cervix: can change in viscosity, before ovulation it is watery (easy flow), post-ovulatory it is thick (decreased flow)
*propulsion in uterus: transport in uterine cavity is fast, aided by contractions of uterine myometrium
*entry to uterine tubules:sperm enter uterine tubules quickly after ejaculation but must undergo capacitation to fulfil fertilisation
what is meant by capacitation of sperm
-occurs in isthmus of uterine tubules
-two key events (hyperactivity and chemical changes)
-can take up to 10 hours
list inhibitory factors of sperm transit
-destroyed by vaginal acid
-destroyed by defence cells
-fail to penetrate cervical mucous
-enter wrong uterine tubule
list productive factors of sperm transit
-propulsion via myometrium contraction
-collection via cervical contractions
-motility via flagellum
-chemical attractants (not proven)
what is meant by hyperactivity in the context of capacitance
-sperm flagellum beats more vigorously,
-enables faster swimming and exertion of pressure on layers surrounding oocyte
-allows it to pass through the tunnels of ‘jelly’ zona pellucida
what is meant by chemical changes in the context of capacitance
-preparation for the acrosome reaction
-chemical changes that enables enzymatic breakdown of protective coats (granulosa cells) around an egg in preparation for fertilisation
name the two key components that protect oocytes
granulosa cells & zona pellucida
function of follicular (granulosa) cells
provide a protective perimeter for the oocyte
function of zona pellucida
protective coating that provides a layer of obstruction from sperm
define polyspermy
process of multiple sperm fertilising same egg (this exceeds the diploid number)
name the main mechanisms that block polyspermy
depolarisation and cortical granules
describe how depolarisation blocks polyspermy
-influx of sodium depolarises the oocyte
-sperms are electrically repelled by the egg
-hence are propelled away from egg
describe how cortical granules block polyspermy
-cortical granules rush to egg surface
-bind to and stregthen zona pellucida
-acrosomal enzymes are insufficient to penetrate the zona pellucida
Outline process of pre implantation
-Day 0: Fertilization is completed with the fusion of sperm and egg nuclei, forming a zygote.
-Days 1-3: The zygote undergoes mitotic divisions (cleavage), progressing to a 2-cell, 4-cell, and then an 8-cell stage.
-Day 4: The zygote forms a solid ball of cells called a morula, which begins descending towards the uterus.
-Day 5: The morula proliferates and differentiates into a blastocyst, consisting of an outer layer (trophoblast) that will become the placenta, and an inner cell mass (embryoblast) that will become the embryo.
- Days 6-7: Trophoblast cells release enzymes to break down the zona pellucida (embryo hatching). The blastocyst adheres to the uterine lining with its inner cell mass side
whats a zygotę
single-cell structure formed by the fusion of sperm and egg during fertilisation
whats the morula
solid ball of cells resulting from early divisions of zygote, preceding formation of blastocyst
whats a blastocyst
-fluid filled structure
-consisting of outer layer of cells (trophoblast) and inner cell mass (embryoblast)
-blastocyst implants into uterus during early development
whats embryo stage
-stage of development from implantation of blastocyst until end of 8 weeks gestation
-characterised by organ system formation
whats foetal stage
-stage of prenatal development form ninth week until brith
-organs continue to mature
-organism becomes more recognisable as human
define implantation
crucial step in reproduction where a fertilised embryo attaches to the lining of uterus
Outline process of implantation
Day6-blastocyst hatches, exposed to uterine fluid, rapid growth and division occur
Day7-blastocyst contacts and adheres to uterine lining
Day8-trophoblast cells divide, formation of cellular and syncytial trophoblast, penetration of endometrial lining, chorion formation and hCG secretion
Day9-enlargement and spread of syncytial trophoblast, erosion of uterine glands villi development, lacunae formation and placenta initiation
whats hCG stand for
human chorionic gonadotropin
Describe role of hCG in maintaining pregnancy
-produced by cells of developing placenta
-helps to maintain corpus luteum, which continues to produce oestrogen and progesterone
-this prevents menstruation and early pregnancy
-helps develop foetal gonads and stimulates production of other hormones in pregnancy
when are hCG levels highest
8-9 weeks
why do hCG levels drop after week 8/9
placenta itself takes over (from the corpus luteum) to produce oestrogen and progesterone
whats hCG used for in a practical sense
used as a marker for pregnancy and can be detected via various lab tests eg blood tests or home tests
abnormal hCG levels can be indicative of
ectopic pregnancy or foetal abnormalities
when do hCG levels plateau/decline at slower rate
around 26 weeks onwards
name the layers of endometrium
stratum basalis and stratum functionalis
list the three parts of prenatal period and length of each
fertilisation (week 2)
embryonic (week 2-8)
foetal (week 8+)
describe the primitive/fertilisation period of prenatal development
early stages of development; primitive germ layers are formed
describe embryonic period of prenatal development
major organ systems are formed; embryo is established
describe foetal period of prenatal development
organs systems mature; developing child (foetus) is established
define developmental age
the date of fertilisation to the date of birth
define clinical age
date of mothers’ last menstrual period to date of birth
what does the ectoderm give rise to
skin, NS , skull, enamel, ear, adrenal medulla, pituitary gland and eye
what does the mesoderm give rise to
muscle, viscera (gut), bones, blood and lymph
what does the endoderm give rise to
epithelial lining of ducts, organs, viscera and primordial germ cells
what two structures develop ‘early’ in the NS
neural tube and neural crest
what structures develop moderately/middle in NS
prosencephalon
mesencephalon
rhombencephalon
what structures develop late in NS
telencephalon
diencephalon
metencephalon
myelenchephalon
what are the mature structures of NS
CC
thalamus
hypothalamus
hypothalamus
epithalamus
subthalamus
cerebral peduncles
tegmentum
pons
cerebellum
medulla
spinal chord
sensory neurons
autonomic neurons
glial cells
neural tube divides into
prosencephalon
mesencephalon
rhombencephalon
prosencephalon divides into
diencephalon and telencephalon
mesencephalon divides into
cerebral peduncles and tegmentum
rhombencephalon divides into
metencephalon
myelencephalon
spinal chord
neural crest divides into
sensory neurons
autonomic neurons
glial cells
telencephalon divides into
cerebral cortex
diencephalon divides into
thalamus
hypothalamus
epithalamus
subthalamus
metencephalon divides into
pons and cerebellum
myelencephalon divides into
medulla
when does neural development begin
around third week of embryonic development (ectoderm thickens and forms neural plate)
Describe cardiovascular system development
-begins during the third week of embryonic development
-starts as a simple tube-like structure and undergoes complex changes to develop into four chambered organ
-blood vessels and arteries also develop
Describe MSK system development
-develops from mesoderm germ layer
-skeletal system begins to form as mesenchymal cells condense and differentiate into cartilage and bone
-limb buds emerge –> arms, legs
-muscles and CT develop from mesodermal cells –> skeletal system
How many main stages of placental development are there
5
Describe the first stage of placental development
*week 1-2
-apposition and attachment
-blastocyst approaches and attaches to endometrium of uterine wall
Describe the second stage of placental development
*week 2-3
-implantation and invasion
-blastocyst burrows into uterine wall
-trophoblast differentiates into cytotrophoblast and syncytiotrophoblast
-syncytiotrophoblast invades endometrium and forms chorionic villi
Describe the third stage of placental development
*weeks 3-5
-syncytiotrophoblast infiltrates maternal blood vessels
-blood vessels undergo remodelling
-remodelled blood vessels provide maternal-foetal blood supply
Describe fourth stage placental development
*week 5-12
-chorionic villi grow extensively
-increasing surface area
-maternal-foetal exchange occur through villi walls
-placenta develops umbilical arteries and veins
-placenta acts as a barrier and facilitates nutrient and gas exchange
Describe fifth stage of placental development
*12+ weeks
-growth and maturation ‘
-placenta continues to grow with the foetus
-adapts to developing foetal needs
-protects the foetus
-expelled during childbirth
when is placental weight greatest
around 80 days gestation
when does placenta start to form
30 days gestation
what is maximal placenta weight
around 700 grams
list the components of the placenta
umbilical cord
maternal arteries
maternal veins
placental membrane
intervillious space
chorionic billus
foetal artery
foetal vein
function of umbilical cord
-provide a connection between developing foetus and placenta
-allowing for exchange of oxygen, nutrients and wastes
function of maternal arteries
transport deoxygenated blood away from foetus and towards placenta
function of maternal veins
transport oxygenated blood towards foetus and away from placenta
function of placental membrane
enables diffusion of nutrients from maternal to foetal blood (vice versa)
function of intervillious space
-pools of maternal blood
-form a reservoir of nutrients eating to interact with foetal blood
function of chorionic villus
facilitate exchange of oxygen, nutrients and waste products between maternal and developing foetus during pregnancy
function of foetal artery
transport oxygenated blood from placenta to developing foetus , providing essential nutrients and oxygen for growth and development
function of foetal vein
transport deoxygenated blood and wastes away from placenta
list the functions of the placenta
respiration
excretion
nutrition
immunity
endocrine
what is meant by the placenta having a ‘respiratory’ function
the foetus is bathed in amniotic fluid, cannot breathe t/f acts as pseudo-lung
what is meant by the placenta having a ‘excretory’ function
maintains balance of bicarbonate, H+, urea and creatine through their diffusion across placental membrane
what is meant by the placenta having a ‘nutritional’ function
-foetus can’t eat while in womb
-mother ingests carbs and nutrients which diffuse across placental membrane and enter foetus
-hence mother must have nutrient rich diet
what is meant by the placenta having a ‘immune’ function
-antibodies from past immunity can cross placental membrane and enter foetus
-this protects the foetus from any immune conditions mother may contract during pregnancy
what is meant by the placenta having a ‘endocrine’ function
-placental tissue creates hormones that maintain pregnancy
-hCG helps sustain corpus luteum
-oestrogen prepares the tissues for pregnancy (stretch and suppleness)
-progesterone prepares uterus (endometrium) for pregnancy and blood supply
List the main maternal metabolic adaptations to pregnancy
-GFR (increase by 50-85%)
-weight (increase by 11.5-16 kg)
-Blood volume (increase by 45%)
-CO (increase by 30-50%)
-Oxygen (consumption increase by 20%)
-Metabolic rate (increase by 15%)
Describe why weight increases as a maternal adaptation
390g placenta; 3.8kg baby; amniotic fluid and maternal tissue
site of spermiogenesis
near the lumen of SN tubules
functional maturation of sperm occurs in the
epididymis
Describe why GFR increases as a maternal adaptation
increased metabolic waste elimination for mother and foetus
Describe why blood volume increases as a maternal adaptation
expands to provide adequate oxygen and nutrients to foetus and compensate for increased demands
Describe why CO increases as a maternal adaptation
rises to meet the increased demands of growing foetus and expanded blood volume
Describe why oxygen consumption increases as a maternal adaptation
necessary to support growing metabolic needs of the mother and oxygen demand of developing foetus
Describe why metabolic increases as a maternal adaptation
increase to meet higher energy demands for foetal growth, increased blood volume and physiological change
what are some maternal metabolic changes in pregnancy
-pancreatic beta cell mass growth
-increased adipocyte sensitivity
-increases hepatic glycogen storage (initial)
-increased hepatic glucose generation (later)
list the main maternal cardiovascular adaptations to pregnancy
heartbeat (increase by 15bpm)
SV (increase by 10-20%)
CO (increases by 30-50%)
when and why does heartbeat increase in pregnancy
increases throughout pregnancy to supply placenta and maternal tissues for pregnancy
when and why does SV increase in pregnancy
increases in early pregnancy only to supply placental development
when and why does CO increase in pregnancy
increases throughout (greatest extent in early pregnancy)
-supply placenta and maternal tissue for pregnancy
Outline composition of semen
seminal fluid - 65% : fructose (energy for sperm) , prostaglandins (smooth muscle contractions of male and female RS), fibrinogen (Clots sperm cells for protection against female RS)
sperm cell- 4%
bulbourethral fluid <1% alkaline mucous (neutralises the acidity of the urethra) and lubricate the urethra
prostate fluid 30% : milky (proteolytic enzymes that break down the fibrinogen and hence allows sperm to be released into Female RS)
-general antibiotic (seminal plasmin)
-citric acid (metabolism)
whats gastrulation
formation of 3 germ layers
whats neuralation
formation of neural tube
