Essay 2.0 Flashcards
What is the average size of a testis?
4cm length by 2.5cm width
How does the size of the testes change with age?
Size of the testes decrease with age
How many lobules are the testes divided into?
Divided into about 250-400 lobules
What do the lobules in the testes contain?
Each contain 2-4 tightly coiled seminiferous tubules - the actual sperm factories
What surrounds the seminiferous tubules?
Seminiferous tubules are surrounded by smooth muscle
What cells surround the seminiferous tubules and what do they produce?
Leydig cells surround the seminiferous tubules and produce testosterone
What is the prepuce?
Loose skin held in place by the frenulum
What is circumcision?
Circumcision is the removal of the foreskin
What are the three erectile tissues in the penis?
Corpus cavernosa x2 and corpus spongiosum
What does the corpus cavernosa do?
Makes up most of the penis and is superior to the urethra when the penis is erect
What is the function of the corpus spongiosum?
Surrounds urethra - keeps it open during ejaculation
What is the epididymis?
Highly coiled ducts - usually 6-7 cm (6m in total)
What happens to sperm in the epididymis?
Sperm leave the testis and are stored here for a 20 day journey to learn to swim
What happens to sperm during urination?
Sperm ‘constant leak’ from the epididymis and are washed away during urination
How long can sperm be stored in the epididymis?
Several months
If held longer without ejaculation, they are eventually phagocytised.
What is the color of semen attributed to?
Secretion from the prostate gland
Semen is a mixture of sperm and accessory gland fluids.
What is the pH range of semen?
7.3-7.7
Semen requires a medium for sperm to swim in. What does this medium contain?
- Nutrients - Fructose, Amino acids
- Chemicals that suppress the immune response in the females reproductive system
*Spermidine - a compound that prolongs the lifespan of sperm
What is spermidine?
A compound that prolongs the lifespan of sperm
What type of control is an erection an example of?
Parasympathetic control of arterioles
What is released to cause the dilation of arterioles during an erection?
Nitric oxide (NO)
Which structures fill with blood during an erection?
- Corpus cavernosa
- Corpus spongiosum
What characterizes the first ejaculate?
Higher sperm count; prostatic fluid
What characterizes the second ejaculate?
Low sperm count; seminal fluid
What is the typical sperm count during masturbation?
Usually low sperm count
What is the typical sperm count during intercourse?
Usually high sperm count
What happens to the bladder sphincter during ejaculation?
Constricts to prevent expulsion of urine
What physiological action forces sperm and semen into the ductus deferens during ejaculation?
Peristalsis
What is the function of Cowper’s gland?
Produces a thick clear mucus that lubricates the glans penis during sexual excitement
Also known as pre-ejaculatory fluid (pre cum), it neutralizes traces of acidic urine in the urethra just prior to ejaculation.
Where is Cowper’s gland located?
Inferior to the prostate
What is spermatogenesis?
The process of producing male gametes - spermatozoa (sperm)
Occurs in seminiferous tubules.
At what age does spermatogenesis begin?
Age II-14 (puberty)
What is the daily sperm production (DSP)?
400 million
How long does spermatogenesis take?
Around 65 days
What cells surround sperm during spermatogenesis?
Sertoli cells
What role do Sertoli cells play in spermatogenesis?
Support sperm to mature
What initiates meiosis during spermatogenesis?
Increase in testosterone levels at puberty
What does a primary spermatocyte generate?
2 secondary spermatocytes
What is produced by each secondary spermatocyte?
Two haploid spermatids
This results in a total of four spermatids.
What is spermiogenesis?
The final stage of spermatogenesis where spermatids mature into spermatozoa (sperm cells)
How many events are involved in the transformation during spermiogenesis?
7 events
Fill in the blank: During spermiogenesis, enzymes are packed by the _______.
Golgi apparatus
What forms at the front of the sperm during spermiogenesis?
Acrosome
What forms at the back of the sperm during spermiogenesis?
Flagellum
What occurs during mitochondrial multiplication in spermiogenesis?
Forms rings around the proximal portion of the flagellum
What happens to excess cytoplasm during spermiogenesis?
Sloughing off excess cytoplasm
What is the final step in the maturation of a spermatid during spermiogenesis?
Matures into spermatozoa (sperm)
What are the accessory glands associated with the male reproductive system?
Seminal vesicles and prostate
The seminal vesicles are a pair of glands, while the prostate is a single organ.
What is the length of the seminal vesicles?
10-15 cm long tubular structure, coiled to measure 4-5 cm in length
What is the primary function of the fluid secreted by the seminal vesicles?
Neutralises vaginal acidic pH
The fluid comprises approximately 70% of semen volume and contains fructose and absorbic acid.
What components enhance sperm motility in seminal fluid?
Fructose and absorbic acid
Where do sperm and seminal fluid mix during ejaculation?
Ejaculatory duct
What is the size of the prostate gland?
3x4x2 cm
What percentage of semen fluid is secreted by the prostate?
30%
What is the role of prostate-specific antigen (PSA) in semen?
Makes semen thinner
What hormone is secreted by the prostate to ensure sperm cell motility?
Spermine
What is dihydrotestosterone (DHT) in relation to testosterone?
Biologically active form of testosterone
What is a key characteristic of the chemical composition of semen?
Responsible for the characteristic odour of semen
What are the ovaries?
Pair organs located on either side of the uterus
Ovaries are essential for producing oocytes and hormones.
What are ovarian follicles?
Tiny sacklike structures embedded within the cortex of the ovaries
Each follicle contains an immature egg called an oocyte.
List the stages of maturation of ovarian follicles.
- Primordial follicle
- Primary follicle
- Secondary follicle
- Late secondary follicle
- Graafian follicle
These stages are distinguished by their structure.
What is the Graafian follicle?
A mature follicle that extends from the cortex and bulges from the surface of the ovary
It is involved in ovulation.
What occurs during ovulation?
One follicle ejects its oocyte from the ovary
After ovulation, the ruptured follicle transforms into the corpus luteum.
What is the female duct system?
Includes the fallopian tubes, uterus, and vagina
These structures are involved in the reproductive process.
What is the function of the fallopian tubes?
Receive the ovulated oocyte and are the site where fertilisation usually occurs
The tubes are approximately 10cm long and 1-4mm in diameter.
What are fimbriae?
Finger-like projections on the fallopian tubes that help catch the released oocyte
Fimbriae are important for the fertilization process.
What is the size of the uterus in adults?
7.5cm in length, 5cm in width, and 2.5cm in thickness
The size can be smaller in women who have never been pregnant.
What are the three layers of the uterine walls?
- Perimeterium
- Myometrium
- Endometrium
These layers have distinct functions in the reproductive process.
What is the vagina?
A thin-walled tube, 8-10cm long, lying between the bladder and rectum
It serves as the birth canal.
What is the pH of the vagina, and why is it important?
pH 4, helps keep it healthy
The acidic environment protects against infections.
In virgins, what happens to the mucosa near the vaginal orfice?
Forms an incomplete partition called the hymen
What is the function of the uterus?
To receive, retain, and nourish a fertilised ovum
What is the hymen?
Thin fold of mucous membrane which extends across the vaginal opening (introitus)
The actual function of the hymen remains unclear.
What happens to the hymen during coitus?
Ruptures, leaving small tags of tissue around the introitus, termed hymenal carunuculae
What are the components of the external genitalia (vulva)?
- mons pubis
- labia
- clitoris
- Bartholin’s gland
- Skene’s gland
What is the function of Bartholin’s gland?
Secretes fluid to lubricate the vagina
Where do the ducts of Bartholin’s gland open?
On the surface of the vulva
What is the function of Skene’s gland?
Secretes fluid to lubricate the urethral opening and anti-microbial factors to protect the urinary tract from infections
What is the Tanner scale used for?
To classify the stages of puberty
What is the Tanner stage 2?
Breast bud stage, increased areola
What occurs in Tanner stage 3?
Further enlargement of breast and areola
Describe Tanner stage 4.
Areola and papilla (nipple) form secondary mound above level of breast
What defines Tanner stage 5?
Mature stage: projection of papilla only, related to recession of areola
What is oogenesis?
Series of events to produce a secondary oocyte
How long does oogenesis take to complete?
Takes years to complete
How many polar bodies are produced during oogenesis?
Up to 3 polar bodies
What happens to the polar bodies produced during oogenesis?
They eventually degenerate and contain little or no cytoplasm
What is the purpose of polar bodies in oogenesis?
Ensures that the secondary oocyte has all the nutrients for its 6-7 day journey to the uterus
How many oocytes originally exist?
Approximately 7 million
How many oocytes are programmed to die?
About 5 million
How many oocytes remain inactive for around 14 years?
2 million
How many oocytes remain at puberty?
250,000
What hormone activates several oocytes each month?
LH (Luteinizing Hormone)
What happens to the activated oocytes each month?
Only one is selected to produce two haploid cells: one first polar (smaller) and one secondary oocyte (larger)
Describe the process of sperm penetration during oogenesis
An ovum is produced, and there is a joining of 23 paternal and 23 maternal chromosomes
What happens to the oocyte during oogenesis if there is no sperm penetration?
The oocyte simply deteriorates
How many oocytes are typically released in a woman’s lifetime?
Only around 500 oocytes are released out of the 250,000 available
Define the ovarian cycle
The ovarian cycle consists of events associated with oocyte maturation, split into 2 phases: the follicular phase and the luteal phase
What occurs during the follicular phase of the ovarian cycle?
Lasts from days 1 to 14, during which the oocyte is released from the Graafian follicle around day 14, marking ovulation
Explain the process of ovulation
When the ovary expels the secondary oocyte, which is triggered by increased levels of LH
What percentage of women ovulate more than one oocyte, and what can this result in?
1-2%
May result in fraternal (non-identical) twins
How do identical twins occur?
Result from 1 sperm fertilising one oocyte, and the egg splits early on after fertilisation
Describe the luteal phase of the ovarian cycle
Lasts from days 14 to 28, during which the ruptured Graafian follicle collapses to form the corpus luteum
What is the function of the corpus luteum?
Secretes oestrogen and progesterone
What happens to the corpus luteum if pregnancy occurs?
The corpus luteum persists until the placenta is ready to take over hormonal-producing duties
What occurs to the corpus luteum if there is no pregnancy?
The corpus luteum degenerates in about 10 days, forming the corpus albicans
Define corpus albicans
A fibrous scar that results from the involution of the corpus luteum if fertilisation does not occur;
It’s Latin for ‘whitening body’ due to the white appearance of the fibrous tissue
Describe the menstrual phase for the uterine cycle
Occurs from day 1 to 5, during which menstruation takes place. The endometrium detaches due to hormone dependence, leading to bleeding that lasts for 3-5 days
What happens to the ovarian follicle by day 5 of the uterine cycle?
The growing ovarian follicle begins to secrete oestrogen
How does the endometrium change from day 6 to 14 of the uterine cycle?
The endometrium rebuilds itself, influenced by oestrogen
What role does cervical mucus play during days 6 to 14 of the uterine cycle?
Cervical mucus thins during this phase, facilitating the passage of sperm into the uterus
When does ovulation occur in the uterine cycle and what triggers it?
At the end of the follicular phase (days 6-14) in response to LH from the anterior pituitary
What transformation occurs to the ruptured follicle after ovulation?
After ovulation, LH converts the ruptured follicle into a corpus luteum
What is the primary function of the endometrium during the secretory phase (days 15-28)?
The endometrium prepares for embryo implantation
What happens during the secretory phase and what is its source?
Progesterone increases during the secretory phase, produced by the corpus luteum
How does the anterior pituitary respond to increased progesterone levels?
In response to increased progesterone levels, the anterior pituitary reduces LH secretion
What happens to the corpus luteum if fertilisation does not occur?
The corpus luteum degenerates towards the end of the secretory phase
What occurs to the corpus luteum if progesterone levels decrease?
The endometrium sheds, leading to menstruation
Describe the process from oocyte to zygote during fertilisation in terms of timing and location
Fertilisation usually occurs in the fallopian tube, with sperm needing to reach the oocyte within 24hrs and the fertilising power of sperm lasting 24-48hrs
Describe the role of sperm chromosomes in zygote formation
Zygote formation occurs when the sperm’s chromosomes combine with those of a secondary oocyte, producing a diploid zygote
How does capacitation affect sperm before fertilisation?
Sperm must be capacitated over 10hrs, which makes the sperm membranes fragile and initiates the breakdown of acrosomes to release enzymes necessary for fertilisation
During the acrosomal reaction for fertilisation what are oocytes encapsulated by?
Corona radiata
Zona pellucida
Explain the acrosomal reaction during fertilisation
Sperm attach to a receptor (ZP3) on the zona pellucida, causing the acrosomal heads to break and release enzymes that digest holes in the zona pellucida
What mechanisms prevent polyspermy during fertilisation?
Polyspermy is prevented by the release of Ca2+ from the oocytes endoplasmic reticulum, which triggers a cortical reaction that destroys the ZP3 receptors on the zona pellucida, preventing further sperm entering the oocyte
Describe the cleavage and blastocyst formation process after fertilisation
Within 36hrs after fertilisation, the zygote undergoes cleavage to produce 2 identical cells called blastomeres, which continue to divide 4,8,16 (morula)
This allows for nutrient uptake and waste disposal
What happens to the zona pellucida by day 4 after fertilisation?
The zona pellucida breaks down, and the inner stucture is referred to as a blastocyst
What is the significance of the cortical reaction in fertilisation?
It prevents additional sperm from entering the oocyte after the first sperm has successfully fertilised it
How many sperm typically reach the oocyte during fertilisation?
Only a few thousand
Describe the structure of a blastocyst
A fluid-filled hollow sphere composed of a single layer of larger, flattened cells, known as trophoblast cells and a cluster of 20-30 rounded cells called inner cell mass
Define the first trimester of pregnancy
Lasts from 1st day of last normal menstrual period to 12 weeks and 6 days, encompassing early pregnancy from 0-10 weeks
How is the 2nd trimester of pregnancy characterised?
Spans from 13 weeks 0 days to 27 weeks 6 days of gestation and involves several measurements known as biometry
List the routine measurements taken during the 2nd trimester biometry
*Head circumference (HC)
*Biparietal diameter (BPD)(this is the diameter of baby’s head)
*Abdominal circumference (AC)
*Femur length (FL)
What is the purpose of biometry in pregnancy?
To compute the estimated fetal weight (EFW) and may be extrapolated to find the estimated date of delivery (EDD)
How is the date of delivery (EDD) calculated?
Based on parameters such as HC,BPD,AC and FL, with a generally accepted error margin of +/-7 days
Describe the 3rd trimester of pregnancy
The final trimester in a human pregnancy, lasting from 28 weeks 0 days of gestation to term which is typically between 38-40 weeks and
In implantation, what role does human chorionic gonadotropin (hCG) play in pregnancy?
hCG, secreted by trophoblast cells, maintains the viability of the corpus luteum and is detectable in blood or urine 1-2 weeks after fertilisation
How is hCG related to pregnancy tests?
All pregnancy tests used today detect the presence of hCG in blood or urine as an indicator of pregnancy
Describe the timeline of implantation and its completion
Implantation takes about 5 days and is completed 12-15 days after ovulation, just before the endometrium normally sheds
How does the corpus luteum affect the menstrual cycle during early pregnancy?
The corpus luteum continues to secrete progesterone, which blocks the menstrual cycle
What role does the placenta play between the 2nd and 3rd month of pregnancy?
The placenta produces progesterone as the corpus luteum degrades and the ovaries remain inactive until after birth
What happens if implantation fails after about 7 days?
The blastocyst spontaneously aborts, with 30% of implanted embryos later miscarrying due to genetic problems, uterine malformation or unknown reasons
When does embryonic development from gastrula to fetus occur
During the early stages of pregnancy
What transformation occurs during implantation of embryonic development?
The blastocyst is converted to gastrula
List the extra-embryonic membranes present during early development
Amnion
Yolk sac
Allantois
Chorion
What is the function of the amnion?
Filled with amniotic fluid and the sac extends all the way around the embryo, providing protection and homeostasis for the embryo.
What is the role of the yolk sac in early development?
Serves as a source of nutrients and the earliest blood cells and vessels, and it forms part of the digestive system in later development
Describe the function of the allantois
Serves as a structural base for the umbilical cord
What does the umbilical cord contain?
*Connective tissue (Wharton’s jelly)
*2 arteries and 1 vein
What is the function of the chorion?
The chorion forms the placenta and encloses the embryonic body and all other membranes
Describe the function of the umbilical arteries in fetal circulation
The umbilical arteries carry deoxygenated, waste-laden blood from the fetus to the placenta
Explain the role of the umbilical vein in fetal circulation
Transports oxygenated, nutrient-rich blood from the placenta to the fetus
How does the ductus venosus (DV) contribute to fetal circulation?
Transports oxygenated and nutrients-rich umbilical venous blood to the brain and myocardium (bypassing the fetal liver)
Define the foramen ovale and its significance in fetal circulation
A small opening in the inartrial septum that allows blood to flow directly from the right atrium to the left atrium, bypassing the non-functional lungs of the fetal heart
What is the function of the ductus arteriosus in fetal circulation?
Blood enters the right ventricle and is pumped out the pulmonary artery.
The ductus arteriosus transfers most of the blood directly from the pulmonary artery into the artery, helping bypass the pulmonary circuit
Describe the appearance and cause of linea nigra during pregnancy?
A dark vertical line that appears on the abdomen in about 75% of all pregnancies, caused by increased melanocyte-stimulating hormone made by the placenta
What is Chadwick’s sign and when is it observed during pregnancy?
The bluish discolouration of the cervix, vagina and vulva due to increased blood flow, observed 6-8 weeks after conception
Occurs in 95% of pregnancies
How do the hepatic veins and ductus venosus interact in fetal circulation?
Both the hepatic veins and ductus venosus empty into the inferior vena cava, which conveys oxygenated blood to the right atrium
Explain the significance of the umbilical arteries and vein in the context of maternal-fetal exchange
The umbilical arteries carry waste and deoxygenated blood away from the fetus to the placenta, while the umbilical vein brings oxygenated blood and nutrients from the placenta to the fetus
Describe the process of parturition (birth)?
Occurs approximately 280 days after the last menstrual period and involves a series of events that expel the infant from the uterus, known as labour
How does oestrogen influence the myometrium during parturition?
Increased oestrogen stimulates myometrial cells (middle layer of uterus) to form many oxytocin receptors and antagonises progesterones influence leading to weak, irregular contractions known as Braxton Hicks contractions
Define Braxton Hick contractions
Weak, irregular uterine contractions that occur during pregnancy often referred to as false labour
What role do oxytocin and prostaglandin play in labour?
Both are released close to birth; oxytocin makes the myometrium sensitive and sustains labour, while prostaglandin triggers true labour
How does the hypothalamus contribute to the labour process?
Activates the posterior pituitary to increase oxytocin release, which is part of a positive feedback mechanism that enhances uterine contractions
This oxytocin weakens the placental grip on the endometrial wall
Explain the stages of labour
Stage 1: cervix dilates to about 10cm
Stage 2: expulsion, lasts from full dilation to delivery
Stage 3: delivery of placenta
What occurs during stage 1 of labour?
Cervix dilates to about 10cm, contractions of uterus and vagina occur, and the infants head moves into the pelvic region, a process called engagement
How long does stage 1 of labour typically last?
6-12 hours
Describe the events of stage 2 labour?
Lasts from full dilation to delivery, with contractions occurring every 2-3 minutes, each lasting about 1 minute and this stage lasts approximately 50 minutes to 2 hours
What is crowning in the context of childbirth?
When the baby’s head distends to the vulva during the expulsion stage of labour
Describe the placental stage of delivery
Delivery of placenta and its attached fetal membrane, also known as the afterbirth, and typically lasts about 30 minutes
How can postpartum bleeding occur after delivery?
If some placenta remains inside the uterus after delivery
Define the neonatal period
4-week period immediately after birth
What is assessed in an infant’s physical status 1-5 minutes after birth?
Based on appearance (skin colour), pulse (heart rate), grimace (reflex irritability), activity (muscle tone), respiration, known as the APGAR score
How is a premature infant defined?
One born before 37th week of gestation and weighing less than 250g (5.5lb)
What challenges do premature infants face regarding lung function?
More difficulty keeping their lungs inflated due to insufficient surfactant production, which typically occurs during the last months of prenatal life
What is the transitional period after birth?
Occurs 6-8hrs after birth, characterised by alternating periods of increased activity and sleep, along with frequent gagging as the baby regurgitates mucus and debris
How often do waking periods for a newborn typically occur?
Typically proceed with hunger periods every 3-4hrs
What is meconium?
Occurs within 48hrs after birth.
Is the baby’s first faeces, characterised by, almost tar-like consistency, made up of mucus, amniotic fluid, and everything the baby ingested while in the uterus
Define lactation
The production of milk by the mammary glands
Describe the role of prolactin during pregnancy?
Promotes the production of milk and its increased levels inhibit the ovarian cycle by dampening the release of GnRH from the hypothalamus, which in turn reduces FSH and LH from the pituitary
What is colostrum and its significance?
A yellowish fluid secreted initially after childbirth during the lactation period, containing antibodies that protect the infant
How does oxytocin function in milk ejection?
Causes the let down reflex, which is the actual ejection of milk from the mammary glands
Define the relationship between prolactin and the ovarian cycle
Increased levels of prolactin inhibit the ovarian cycle by suppressing the hypothalamic release of GnRH, leading to decreased levels of FSH and LH from the pituitary
What stimulates the anterior pituitary to secrete prolactin during pregnancy?
Increased oestrogen and progesterone at the end of pregnancy stimulates the anterior pituitary to secrete prolactin
What hormonal changes occur at the end of pregnancy related to lactation?
There’s an increase in oestrogen and progesterone, which are important for the initiation of lactation
