Reproductive Flashcards
Gonad formation
Formed from the gonadal ridges. Are in the upper lumbar region (back)
Moving testes
In humans the testes migrate through the abdomen and into the scrotum during development. Probably controlled by androgens.
Gubernaculum
A ligament attaches the testes to the posterior abdominal wall that does not elongate with body growth. Drags the testes down.
The female gubernaculum
Gives rise to the round ligament and aids in mullerian development
Cryptorchidism
Failure of the testes to descend. Some species have it naturally. Results in arrested spermatogenesis. Normal endocrine function
Monotremes
Means one hole. Monotremes are permanently cryptorchid. Some species have testes that move between the scrotum and the abdominal cavity.
Temp of testes
The testes in the scrotum have a temperature 4-7 degrees lower than core body temperature. The effects of cryptorchidism can be mimicked by warming the testes
What separates the chambers of the testes
Perineal raphe
Cremaster muscle
Lies under the skin of the scrotum and control the location of the scrotum relative to the body. Contracts in response to cold to draw the testes closer the body.
Testicular structure- fibrous sheath and lobule name
Each testicle is covered by a fibrous sheath called the tunica albuginea. Each testicle is divided into lobules containing seminiferous tubules.
The cycle of the seminiferous epithelium
Time taken for a sperm to be produced from a germ cell is constant. In any one section, all parts of the production of sperm are synchronised. A cycle is every 16 days
Spermatogenic wave
Responsible for continuous supply, each segment is a stage ahead of the preceding segment
Epididymis
A muscular tube with an epithelial pseudostratified lining. Site of sperm maturation. Sperm spends 13 days
Head (caput)
Receives sperm from rete testis. Contains stereocilia for absorption of fluid. Sperm cannot fertilise and can not move.
Body (corpus)
Convolutions decrease and fluid content decreases
Tail (caudal) of epididymis
Stereocilia reduced
Muscularity increased - moving to three layers. Sperm moves by peristaltic action. Sperm now more concentrated. Epididymis are capable of fertilisation and move
Vas Deferens
Sperm storage. 3 muscular layers. Inner longitudinal layer, middle circular layer, outer longitudinal layer.
Just prior to the prostate gland the lumen becomes enlarged and folded with many crypts. Additional sperm storage called ampulla
Absence of Vas Deferens
Congenital absence of the Vas (CAVD). Common in men with cystic fibrosis. Usually bilateral both vas are missing and though to be due to genetic mutations
What do the ligaments suspending the uterus and ovaries do?
Position the organs because they don’t want movement and correctly align them as the fallopian tubes are connected to the uterus but not the ovaries
What does the ovarian ligament do?
Connects the ovaries to the uterus
What does the ovarian cycle do?
Allow production of oocyte that is ready to be fertilised. Oocytes are produced during gestation
What does the broad ligament do?
Stops lateral movement of the uterus
What does the suspensory ligament do?
Connects the ovaries to the pelvic wall and contains the ovarian arteries/veins
Primordial follicle
Resting - flattened granulosa cells
Primary follicle
Activated - single layer of cuboidal granulosa cells
Secondary follicle
Multilayered granulosa cells
Tertiary follicle
Antrum formed
How long does it take from the time activation to when a follicle forms an antrum and is capable of ovulation
85 days
Which position does the uterus face?
Anteverted, ie the top of the uterus faces forwards. Fetus has to turn 90º to be born via the vagina
Uterus properties
7.5cm long and pear shaped
Non-pregnant uterus has a luminal volume of 10mls
Pregnant uterus contain 5L of baby, amniotic fluid and placenta.
Uterus sections
Top of the uterus - fundus
Bottom of the uterus - cervix
3 main layers:
Serosa (perimetrium)
Muscular myometrium (largest)
Inner endometrium
Myometrium
90% of uterine tissue
Main function is the forceful expulsion of the fetus at parturition (delivery)
10mm thick and doesn’t change during the menstrual cycle
Contractions
Proliferative phase - contractions upwards aiding sperm transport
Secretory phase - contractions downwards aiding embryo transport
Decidual reaction (preparation for implantation)
Stroma of the endometrium swollen with fluid. Stroma fibroblasts expand and fill with glycogen (energy source) Occurs spontaneously each menstrual cycle
Window of implantation
Can only implant in endometrium during a 48 hour window and determined by expression of adhesion molecules that interact with trophectoderm on the blastocyst and possibility by the appearance of pinopodes. Usually on day 21
Uterine blood supply
Spiral arteries supply blood to the endometrium and the placenta during pregnancy. There are tonically active. During menstruation the spiral artery terminal segments are lost and to prevent exsanguination (bleeding out) the spiral arteries undergo spasm. In the proliferative phase the spiral arteries grow very rapidly into spring-like coils.
Ectopic implantation
Implantation not in the uterus, most common in the fallopian tube.
Cervix - ecto/endo epi
The outmost layer of the endocervix is single columnar epithelium
Ectocervix is lined by a multi-layered squamous epithelium
During a menstrual cycle the vagina induces a transitional zone between the ecto and endo cervix
Trimester dates
1st trimester - conception until 12 weeks
2nd trimester - 13 weeks until 24 weeks
3rd trimester - 25 weeks until term (36-40)
Lacunar stage days 8-12
Primitive syncytium invades the uterine decidua forming gaps in the maternal tissue or lacunae the trophoblast protrusion are called trabeculae. The lacunae tap the maternal blood vessels
Beginning of the villous period Day 12 -14
Cytotrophoblasts proliferate and invade the trabeculae - these become primary villi. Lacunar system is now the intervillous space. At day 14 the extraembryonic mesenchyme cells invade the primary villi forming secondary villi
Tertiary Villi (18 - 20 days)
Capillaries form in the villi. All villi are tertiary. The vessel connect to the umbilical vessels carrying blood to the fetus
What percent of contraception are lost in the fest few days
60%
Villus
Branch of the placenta
Trophoblasts
Epithelial cells unique to the placenta - multiple subtypes all derived from trophectoderm of the blastocyst
Villous cytotrophoblast
Trophoblast progenitor cell type found mainly in the first trimester underlying the syncytiotrophoblast
Syncytiotrophoblast
Surface layer of the placenta formed by fusion of VCTB. STB does not replicate but is replaced by fusion of additional VCTB
Extravillous cytotrophoblast
Differentiated cells that have migrated out of the villous placenta towards the maternal tissues
Primitive synctium
The invasive multinucleated cell found in the lacunar phase
Villi regression forming smooth chorion
The placenta forms a sphere surrounding the embryo but as gestation progresses:
Villi disappear to the sides and luminal aspect regress to form the smooth chorion (membrane that a baby lives in)
Only villi basal to the implantation site remain as the placenta
Anchoring villi
Anchor the placenta to the uterine tissue and also transform the maternal spiral arteries.
Anchoring villi processes
A few villi cytotrophoblasts break through the syncytiotrophoblast.
The cytotrophoblast spread laterally around the implantation site forming a cytotrophoblast shell
The trophoblast shell remains in contact with the maternal tissue throughout gestation
Columns of cytotrophoblast continue to stream out of these anchoring villi to invade the decidua and spiral arteries during the first and second trimesters
Floating villi (nearly all are in early gestation)
Do not have contact with the maternal tissues but are suspended in the intervillous space. They are responsible for the exchange and barrier functions of the placenta
Trophoblasts transforming the spiral arteries
Extravillous trophoblasts break through the syncytiotrophoblast layer of the placental villous and invade the spiral arteries
The spiral arteries transform to wide-bore tubes with no muscular wall, lined by trophoblasts and can’t respond to stimuli
What happens if a pregnant mother contracts her blood vessels?
The spiral arteries contract and the baby loses its blood supply. Thats why the spiral arteries need to be hollowed out.
Decidual reaction
The stromal cells of the decidua are swollen and store glycogen and upon implantation this reaction is enhanced
Layers of decidua
Decidua basalis - the decidua underlying the implantation site
Decidua capsularis - the decidua overlying the implantation site
Decidua peritalis - the decidua around the remainder of the uterus
What happens as gestation progresses?
The amniotic cavity enlarges filling the uterine cavity.
The decidua capsularis fuses with the decidua peritalis
Umbilical Cord
-Whartons jelly -> provides turgor
- Consists of a network of myofibroblasts
- Spaces are filled with mucopolysaccharides
Formation of the umbilical cord
Formed from the yolk sac and allantois. The vessels of the umbilical cord are derived from the allantois. 2 arteries (deoxygenated) and 1 vein (oxygenated)
Breast tissue
Mammary glands are modified sweat glands. Derived from tissue that is first in mammary crests that arise in the embryo between the armpit and groin. Abnormal breast development is likely to occur along the lines of the mammary crests
Breast development begins with the formation of mammary buds at 6 weeks
Primary breast bud formation
First development takes place as a down growth of the epidermis
Secondary breast buds
Develop from primary breast bud and then become lactiferous ducts
Derivation of the breast
As gestation progresses the buds develop lumens (become canalised). Canalisation is induced by placental steroids and by birth 15-20 lactiferous ducts are present
Explain breast development and milk production
By birth the breasts are fully developed and could potentially make milk. Milk production requires hormonal stimulus and since the fetus has been exposed to placental and maternal hormones some babies make a secretion called witch’s milk (first 2-3 days after birth)
Structure of the breast
Body - different shapes determined by pectoral fat pad.
Nipple - lactiferous ducts join the skin at the nipple
Areola - Contains sebaceous glands with no oil or hair
15-20 lobes of milk secreting lobules. Each lobule connects to a single lactiferous duct.
Internal breast structures
Adipose tissue of the pectoral fat pad
Supported by ligaments called Cooper’s ligaments. Affect by ages and hormones in pregnancy and become less supportive
Lactiferous ducts
Runs towards the nipple and expands into a lactiferous sinus. The sinuses (15-20) open onto the nipple to allow extraction of milk
Development of the breast
Until puberty the breast ducts don’t have alveoli. They start to develop during puberty due to oestrogen. Resting breasts are dominated by the duct system and fat - not alveoli
Oestrogen and progesterone promote the growth of alveolar buds
Hormones influencing breasts
Oestrogen - essential for breast growth
Progesterone - induces side branching of ducts
Prolactin - necessary for alveolar development but also stimulates casein and lactalbumin mRNAS
Growth hormone - relate to prolactin
Insulin and cortisol - stimulate alveolar epithelial cell division
Breast weights
Non-pregnant woman - 200g
Near term pregnant- 400-600g
Lactating 600-800g
Progesterone and milk
Progesterone seems to prevent major milk production and is a smooth muscle relaxant and prevent milk ejection. Prevents myometrium from contracting as well.
Endocrine control of lactation
Prolactin is produced in large amounts in pregnancy and falls at birth.
Suckling of infant induces secretion of prolaction by the anterior pituitary.
Prolactin is stimulated by a neuroendocrine reflex, cutting the nerves to the nipple prevents this reflex
Prolactin and milk
Prolactin induce production of milk proteins. Duration and extent of suckling correlates with prolactin secretion. Prolactio correlates with level of milk produced.
Milk ejection response
Suckling stimulates synthesis and secretion of oxytocin by the posterior pituitary.
Oxytocin induces the contraction of myoepithelial cells of alveoli causing ejection of milk.
Stimulation of female reproductive tract can induce oxytocin release.
Stimuli such as crying and smell of baby can induce MER
Lactation and fertility (Prolactin suppresses)
Prolactin suppresses secretion of gonadotropins, FSH and particularly LH. Lactating women have no or irregular menstrual cycles.
Supernumerary Nipples
Additional breast tissue can be found along the line of the embryonic milk ridge. Additional nipples can occur on the ridge.
Route of Ejaculate
Testes: Sperm is produced.
Epididymis: Sperm matures and is stored.
Vas Deferens: Sperm travels through this tube during ejaculation.
Seminal Vesicles: Add seminal fluid to nourish the sperm.
Prostate Gland: Adds additional fluid to help sperm mobility.
Ejaculatory Duct: Sperm passes through, mixing with fluids from the seminal vesicles and prostate.
Urethra: Sperm is expelled through the penis during ejaculation.
