9. special systems Flashcards
1
Q
sex vs gender
A
- sex tends to be considered as male or female at birth
- gender is more of a social construct- associate as a man or woman/non-binary
2
Q
genital organs
A
produce gametes and secrete hormones
3
Q
function of hormones in genital systems
A
- control the development and function of reproductive system
- development of sex-specific body form
- typical sex-specific behaviour
- for fertilisation and development of the foetus
4
Q
genital ducts
A
transport and store gametes
5
Q
accessory glands
A
produce secretions to support gametes
6
Q
gonads for male genital system and their function
A
testes
- produce sperm and hormones
7
Q
associated ducts of the male genital system and their function
A
- epididymis
- ductus deferens
- urethra
> transport, store and mature sperm
8
Q
accessory glands of genital system and their function
A
> produce seminal fluid
- seminal glands
- prostate gland
- bulbo-urethral glands
9
Q
external genitals of male reproductive system
A
- penis
- scrotum
10
Q
where do the testes develop and when do they descend?
A
develop in the foetal abdomen and descend at 7th month of development into the scrotum
11
Q
shape and size of testes
A
paired organs with a flattened egg shape
~4cm
12
Q
why are the testes located in the scrotum?
A
located in the scrotum outside the body
> 2 or 3 degrees cooler to protect sperm
13
Q
function of the testes
A
- sperm production (seminiferous tubules, sertoli and leydig cells)
- dual endocrine and exocrine function
- connected to a duct system
14
Q
spermatogenesis
A
process of sperm production
15
Q
seminiferous tubules
A
- the seminiferous tubules are the sites where spermatogenesis (sperm production) takes place
- each testis contains around 300 lobules, and each lobule contains 1-4 seminiferous tubules.
- total length of seminiferous tubules in a single testis can be around 0.5 km.
- Spermatogenesis occurs within the seminiferous tubules, where spermatogonia (stem cells) undergo mitosis and meiosis to form mature sperm cells.
16
Q
site of spermatogenesis
A
seminiferous tubules
17
Q
how many lobules in each testes?
A
~ 300 lobules / testis
> each lobule contains 1-4 seminiferous tubules
= ~0.5km of seminiferous tubules in single testis
18
Q
tunica albuginea
A
- tunica albuginea is a dense fibrous capsule that surrounds the testes
- this capsule has septa (partitions) the subdivide the testis into lobules
- it provides structural support and protection to the testicular tissues
19
Q
interstitium
A
- between the seminiferous tubules, there is a region known as the interstitium
- the interstitium consists of loose connective tissue and is where the Leydig cells are found
- Leydig cells are responsible for producing testosterone (crucial hormone for male reproductive development and spermatogenesis)
20
Q
where are Leydig cells found and what are they responsible for?
A
the interstitium between seminiferous tubules
> responsible for producing testosterone
21
Q
rete testis
A
- the rete testis is a network of tubules where the sperm drain from the seminiferous tubules after spermatogenesis
- the rete testis serves as a conduit for sperm from the seminiferous tubules toward the efferent ductules, which transport sperm to the epididymis
22
Q
efferent ductules
A
- The efferent ductules connect the rete testis to the epididymis.
- These ductules carry immature sperm from the testis to the epididymis, where sperm will mature and be stored.
23
Q
tunica vaginalis
A
- The tunica vaginalis is a serous membrane that surrounds the testis.
- It has two layers:
>Parietal layer: Lines the inside of the scrotum.
>Visceral layer: Directly covers the testis. - The space between these two layers is filled with serous fluid, which reduces friction and allows smooth movement of the testis within the scrotum.
(This structure is important for the protection and movement of the testis.)
24
Q
Epididymis
A
- The sperm that travel through the efferent ductules reach the epididymis where they are stored and mature.
- The epididymis is a tightly coiled tube that runs along the posterior surface of the testis.
- Maturation of sperm occurs in the epididymis, where they acquire motility and the ability to fertilize an egg.
25
where does maturation of sperm occur?
Maturation of sperm occurs in the epididymis, where they acquire motility and the ability to fertilize an egg.
26
stages of sperm production
Spermatogenesis
1. Spermatogonia (stem cells) undergo mitosis to produce primary spermatocytes.
2. Primary spermatocytes undergo meiosis to form secondary spermatocytes and ultimately spermatids.
3. Spermatids undergo spermiogenesis, a maturation process where they develop into spermatozoa (mature sperm).
4. Once mature, sperm are released from the seminiferous tubules and travel through the rete testis, into the efferent ductules, and into the epididymis for final maturation and storage.
27
Testosterone Production by Leydig Cells
The Leydig cells in the interstitial tissue produce testosterone, which is essential for:
- The development of male reproductive organs and secondary sexual characteristics (e.g., facial hair, deep voice).
- Stimulating spermatogenesis within the seminiferous tubules.
- Regulating the production of gonadotropins (LH and FSH) through negative feedback on the hypothalamus and pituitary gland.
28
What are the main components of the scrotum?
The scrotum consists of skin, connective tissue, and dartos muscle.
29
How does the scrotum help in temperature regulation of the testes?
The scrotum maintains the temperature of the testes by adjusting the distance of the testes from the body. Dartos muscle contracts to shrink the scrotum when cold, and cremaster muscle pulls the testes closer to the body. When warm, these muscles relax, allowing the testes to move further from the body.
30
What are the roles of the dartos and cremaster muscles in scrotal function?
The dartos muscle contracts to reduce the size of the scrotum by firming up the skin (cold temperature). The cremaster muscle pulls the testes closer to the body to conserve heat in cold conditions and allows them to hang further when relaxed (heat).
31
Why is it important for the testes to be at a cooler temperature than the rest of the body?
A cooler temperature is essential for spermatogenesis (sperm production). Spermatogenesis requires a temperature lower than the body’s core temperature to maintain optimal sperm production and quality.
32
How does cold weather affect the scrotum and testes?
In cold weather, the dartos muscle contracts and the cremaster muscle pulls the testes closer to the body, reducing the surface area of the scrotum to help preserve heat.
33
What is the raphe and septum, and how do they divide the scrotum?
The raphe is the external ridge dividing the two sides of the scrotum. Internally, the scrotum is divided by a septum, a ridge of connective tissue.
34
What is spermatogenesis and what are the key stages of sperm development?
Spermatogenesis is the process by which spermatogonia develop into spermatozoa (sperm). The process occurs in the seminiferous tubules of the testes, involving the stages of spermatogonia development, meiosis, and differentiation into mature sperm.
35
How many sperm are produced per day, and why is there a high mutation rate in spermatogenesis?
Approximately 70-100 million sperm are produced per day. There is a high mutation rate due to the large volume of sperm produced daily, increasing the likelihood of mutations during cellular division.
36
How long does spermatogenesis take, and where does it occur?
Spermatogenesis takes about 64 days and occurs in the seminiferous tubules of the testes.
37
What is the role of Sertoli cells in the seminiferous tubules?
Sertoli cells nourish and support the development of sperm within the seminiferous tubules. They also help in the regulation of spermatogenesis and the blood-testis barrier.
38
Why do sperm in the epididymis gain motility but are not fully mature?
Sperm gain motility in the epididymis but are not fully mature because they need to undergo capacitation in the female reproductive tract before they are capable of fertilization.
39
What is capacitation, and why is it necessary for sperm to fertilize an egg?
Capacitation is the final maturation step of sperm that occurs in the female reproductive tract. It enables sperm to be capable of fertilizing an egg by altering the sperm’s membrane and increasing its ability to penetrate the egg.
40
Where do the testes begin before they descend into the scrotum?
The testes begin near the kidneys before descending into the scrotum during fetal development.
41
What is cryptorchidism, and what are the potential consequences if not corrected?
Cryptorchidism is the condition where one or both testes fail to descend into the scrotum. If not corrected, it can lead to infertility and increases the risk of testicular cancer.
42
What percentage of cases of cryptorchidism resolve spontaneously?
About 70% of cryptorchidism cases resolve spontaneously.
43
Why is bilateral cryptorchidism associated with infertility and increased testicular cancer risk?
Bilateral cryptorchidism leads to both testes being undescended, which can impair spermatogenesis and result in infertility. It also increases the risk of developing testicular cancer later in life.
44
What structures pass through the inguinal canal?
The inguinal canal contains the ilioinguinal nerve and the spermatic cord, which includes the vas deferens, testicular artery, testicular veins, and autonomic nerves.
1. ilioinguinal nerve
2. spermatic cord
- vas deferens
- testicular veins
- autonomic nerves
45
What is a hernia, and how is it related to the inguinal canal?
A hernia occurs when fatty tissue or bowel protrudes through a weakness in the abdominal wall, often in the inguinal canal, creating a visible and painful lump.
46
What complications can arise from a hernia?
Complications from a hernia include obstruction or strangulation of the bowel, which may require surgery to correct.
47
What structures are found in the spermatic cord?
The spermatic cord contains the vas deferens, lymph vessels, autonomic nerves, testicular artery, pampiniform plexus of testicular veins, cremasteric artery and vein, and the deferential artery.
1. vas deferens
2. lymph vessels
3. autonomic nerves
4. testicular artery
5. pampiniform plexus
6. cremasteric artery and vein
7. deferential artery
48
What role does the cremaster muscle play in the spermatic cord?
The cremaster muscle in the spermatic cord contracts to pull the testes closer to the body, helping in temperature regulation.
49
What are the functions of the deferential artery and pampiniform plexus of veins in the spermatic cord?
The deferential artery supplies blood to the vas deferens, while the pampiniform plexus of veins helps cool the blood entering the testes by absorbing heat from the outgoing blood.
50
What are the main functions of the epididymis?
The epididymis stores sperm, allows them to mature, and facilitates the recycling of damaged sperm. It is also responsible for sperm motility.
51
How do cilia and microvilli in the epididymis contribute to sperm maturation?
Cilia and microvilli increase the surface area in the epididymis to help absorb degenerated sperm and recycle them, as well as to aid in the maturation of sperm.
52
How long do sperm mature and are stored in the epididymis?
Sperm mature and are stored in the epididymis for 12-16 days.
53
Why are sperm in the epididymis not able to fertilize an egg until capacitation occurs?
Sperm are unable to fertilize an egg because they are not fully mature in the epididymis. They must undergo capacitation in the female reproductive tract to acquire the ability to fertilize an egg.
54
What is the function of the vas deferens in the male reproductive system?
The vas deferens transports sperm from the epididymis to the ejaculatory duct, where it is mixed with fluids from the seminal vesicles and prostate to form semen.
55
What is the role of the ampulla in the vas deferens?
The ampulla is the enlarged portion of the vas deferens, where sperm is stored before being mixed with secretions from the seminal vesicles to form semen.
56
How does a vasectomy work and what is its impact on male fertility?
A vasectomy involves cutting and ligating the vas deferens, which prevents sperm from entering the urethra during ejaculation. This results in permanent sterility.
57
Where does the ejaculatory duct empty, and what is its function in ejaculation?
The ejaculatory duct empties into the prostatic urethra, where sperm is mixed with seminal fluids for ejaculation.
58
What is the ductus (vas deferens), and what is its function?
The ductus (vas deferens) is a strong muscular tube that is part of the spermatic cord. Its main function is to transport sperm from the epididymis to the urethra during ejaculation.
59
What type of epithelium lines the vas deferens, and what is its role?
The vas deferens is lined with pseudostratified columnar epithelium with stereocilia. The stereocilia help with the absorption of fluid and the movement of sperm.
60
Describe the path of the vas deferens from the epididymis to the prostatic urethra.
The vas deferens ascends from the epididymis, passes through the inguinal canal, and reaches the pelvis. It enlarges posteriorly to form the ampulla, joins the seminal vesicle duct to form the ejaculatory duct, and empties into the prostatic urethra.
61
What is the ampulla in the vas deferens, and what role does it play?
The ampulla is the enlarged posterior and proximal part of the vas deferens. It stores sperm before ejaculation.
62
What is the significance of the vas deferens in a vasectomy?
In a vasectomy, the vas deferens is cut and ligated, preventing sperm from traveling to the urethra, thus achieving sterilization.
63
Where are the seminal vesicles located in the male reproductive system?
The seminal vesicles are paired glands located posterior and inferior to the urinary bladder.
64
What is the function of the seminal vesicles in semen production?
The seminal vesicles produce and store semen. They secrete a fluid that is rich in fructose and prostaglandins, which nourish sperm and aid in their motility.
65
What percentage of the semen volume is contributed by the seminal vesicles?
The seminal vesicles contribute about 60% of the semen volume.
66
What is the composition of the seminal vesicle secretion, and how does it support sperm?
The seminal vesicle secretion contains fructose (providing energy to sperm), prostaglandins (helping sperm motility), and alkaline secretions (to neutralize the acidic environment of the female reproductive tract).
67
How does the secretion of the seminal vesicles help sperm during ejaculation?
The secretion provides sperm with nutrients and an alkaline environment, which helps protect the sperm and supports their movement through the female reproductive tract.
68
What is the size and location of the prostate gland?
The prostate is about the size of a walnut, 2-4 cm in diameter, and is located inferior to the bladder.
69
How does the prostate contribute to semen production?
The prostate contributes about 30% of the semen volume. It produces slightly alkaline secretions that help liquefy semen, allowing sperm to move more freely.
70
What is the role of prostate-specific antigen (PSA) in semen?
PSA is a protein that liquefies semen after ejaculation, allowing sperm to swim freely.
71
What are common diseases associated with the prostate, and how do they affect male health?
Common diseases of the prostate include prostatitis, benign prostatic hyperplasia (BPH), and prostate cancer. These conditions can lead to urinary problems, pain, and, in severe cases, infertility or cancer.
72
What is the function of the bulbourethral glands in male reproduction?
The bulbourethral glands secrete an alkaline mucus that neutralizes any remaining urine in the urethra and lubricates the urethra, providing a protective environment for sperm during ejaculation.
73
How do the secretions of the bulbourethral glands help sperm during ejaculation?
The alkaline mucus neutralizes the acidity of any residual urine in the urethra and provides lubrication, which helps protect and nourish the sperm during ejaculation.
74
What are the dual functions of the male urethra?
The male urethra has dual functions: it carries urine from the bladder during urination and semen during ejaculation.
75
What are the three segments of the male urethra, and what is their role?
The three segments of the male urethra are:
1. Prostatic Urethra: Receives ejaculatory and prostatic ducts.
2. Membranous Urethra: The shortest segment of the urethra.
3. Spongy (Penile) Urethra: Passes through the penis and receives the duct of the bulbourethral glands.
76
What is hypospadias, and how does it affect male reproductive health?
Hypospadias is a birth defect where the opening of the urethra is located on the underside of the penis, which can affect urination and sexual function.
77
What are the main parts of the penis, and what are their functions?
The penis consists of the root and bulb (which connect the penis to the pelvic bones), the shaft (which contains erectile tissue), and the glans (the head of the penis). The shaft is involved in erectile function, and the glans plays a role in sexual arousal.
78
Describe the structure of the erectile tissue in the penis.
The erectile tissue includes the corpus spongiosum (ventral) and corpus cavernosa (paired, dorsal-lateral), which are columns of vascular tissue that fill with blood during erection.
79
What is the prepuce, and what role does circumcision play in male health?
The prepuce (foreskin) is the skin covering the glans of the penis. Circumcision involves the removal of the foreskin, often for religious, cultural, or health reasons.
80
How much semen is expelled during ejaculation, and what is its composition?
Typically, 2-5 ml of semen is expelled during ejaculation. Semen contains sperm (5% by volume) and fluid from accessory glands (95%), including secretions from the seminal vesicles, prostate, and bulbourethral glands.
81
What is the normal concentration of sperm in semen, and what is considered infertile?
A normal sperm concentration is 50-150 million sperm per ml. A concentration of less than 20 million/ml is considered infertile.
82
How does ejaculation occur in terms of smooth muscle contractions?
Ejaculation is triggered by peristaltic contractions of smooth muscle in the vas deferens, seminal vesicles, prostate, pelvic floor, and base of the penis.
83
How is spermatogenesis regulated by the brain during puberty?
During puberty, GnRH stimulates the pituitary to release LH and FSH, which act on the testes to initiate and support spermatogenesis.
84
What is the role of GnRH, LH, FSH, and testosterone in spermatogenesis?
GnRH from the hypothalamus stimulates the release of LH and FSH from the pituitary. LH stimulates Leydig cells in the testes to produce testosterone (T). Testosterone and FSH promote the function of Sertoli cells, which support the development of germ cells (sperm).
85
How do Sertoli cells regulate spermatogenesis through inhibin production?
Once spermatogenesis reaches sufficient levels, Sertoli cells produce inhibin, which inhibits the production of FSH by the pituitary, helping to regulate and reduce spermatogenesis.
86
What are endocrine disruptors, and how can they affect male reproductive development?
Endocrine disruptors are chemicals that interfere with the body's endocrine system, potentially affecting male reproductive development, particularly in utero.
87
How do endocrine disruptors impact the testes, penis, and overall fertility?
These disruptors can alter the structure of the testes, interfere with sperm production, affect the development of the penis, and increase the risk of testicular cancer and fertility issues.
88
What is the current understanding of the effects of endocrine disruptors on male health?
The exact mechanisms of how endocrine disruptors affect male health are still not fully understood, but research suggests they can impact male fertility, testicular structure, and risk of reproductive cancers.
89
what is the site of fertilisation?
ampulla
90
What is the main function of granulosa cells?
Oestrogen production
91
Which structure is homologous to the prostate?
Skene’s glands
92
During which phase does LH peak?
Ovulation
93
Describe the stages of oogenesis and highlight when meiosis is arrested and resumed.
Oogenesis is the process by which female gametes (oocytes) are formed in the ovaries.
Prenatal Phase:
- In fetal development, ~5 million oogonia are produced.
- These develop into primary oocytes, which enter meiosis I but arrest in prophase I.
- They are stored in primordial follicles.
- By birth, this number drops to ~2 million, and many degenerate before puberty.
Puberty Onwards:
- At puberty, under FSH stimulation, a cohort of follicles begins to mature each month.
- One becomes dominant and forms a primary follicle, then secondary follicle, and finally a tertiary (Graafian) follicle.
- The oocyte completes meiosis I, producing a secondary oocyte and a polar body.
Ovulation
- The secondary oocyte begins meiosis II, but is arrested in metaphase II.
- This oocyte is ovulated and will only complete meiosis II if fertilisation occurs.
Post-fertilisation:
- On sperm entry, meiosis II completes → ovum + second polar body.
- Fusion of male and female pronuclei results in a zygote
94
Compare the histology and function of the uterine tube and uterus.
UTERINE (FALLOPIAN) Tube:
Function: Transports the oocyte from ovary to uterus, site of fertilisation (usually in ampulla).
Histology:
Mucosa: Simple columnar epithelium with ciliated cells to move the oocyte.
Muscularis: Smooth muscle (inner circular, outer longitudinal) for peristalsis.
Serosa: Outer serous membrane.
UTERUS
Function: Site of implantation and support for fetal development.
Histolgy:
Endometrium: Simple columnar epithelium + lamina propria; has:
Stratum basalis (permanent layer)
Stratum functionalis (sheds during menstruation)
Myometrium: Thick smooth muscle layer responsible for contractions.
Perimetrium: Outer serous layer (peritoneum).
Both have smooth muscle layers and epithelial linings, but uterus has complex glandular structure for implantation.
The uterine tube is more involved in transport, while the uterus supports implantation and fetal growth.
95
Discuss the hormonal regulation of the menstrual cycle.
The menstrual cycle (~28 days) is regulated by hypothalamic-pituitary-ovarian axis.
Hormonal sequence:
1. GnRH from the hypothalamus stimulates the anterior pituitary.
2. Anterior pituitary releases:
FSH: Stimulates follicle growth
LH: Causes ovulation and supports corpus luteum
Cycle phases:
- Follicular Phase (Days 1–13):
FSH promotes follicle development
Follicles produce oestrogen
High oestrogen eventually causes LH surge
- Ovulation (Day 14):
LH surge triggers release of secondary oocyte from dominant follicle
- Luteal Phase (Days 15–28):
LH maintains corpus luteum, which secretes progesterone + oestrogen
These hormones maintain endometrium
If no fertilisation, CL (corpus leteum) degenerates, hormones fall, menstruation begins
Oestrogen and progesterone exert negative feedback on FSH/LH
Hormonal contraceptives mimic this to prevent ovulation
96
Explain the impact of PCOS on ovulation and fertility
Polycystic Ovary Syndrome (PCOS):
- A hormonal disorder affecting 1 in 5-10 women
Ovarian impact:
- Many immature follicles (~<8mm) develop but do not mature.
- Ovulation does not occur regularly due to disrupted hormonal signaling.
Hormonal profile:
- High androgen (testosterone) levels
- Irregular LH and FSH ratios
- Low or absent progesterone due to lack of corpus luteum formation
Consequences:
- Anovulation → infertility
- Menstrual irregularities
- Associated with insulin resistance, weight gain, acne, hirsutism
- Increased risk of diabetes, cardiovascular disease, and endometrial cancer
97
What are the external female genitalia?
Clitoris, labia majora, labia minora, and vestibular glands.
98
What are the internal female reproductive organs?
Ovaries, fallopian tubes, uterus, and vagina.
99
What are the two main functions of the ovaries?
Produce oocytes (gametes) and secrete hormones (endocrine).
100
What ligaments support the ovaries?
Suspensory ligament (to pelvic wall) and ovarian ligament (to uterus).
101
What are the two regions of the ovarian stroma?
Outer cortex (with follicles) and inner medulla (with vessels and nerves).
102
What epithelium lines the ovary?
Simple cuboidal germinal epithelium.
103
When do primary oocytes first begin meiosis?
During fetal life.
104
At what stage is meiosis I arrested in oocytes?
Prophase I.
105
When is meiosis II arrested in the oocyte?
Metaphase II, until fertilisation.
106
How many oocytes are ovulated in a lifetime?
Around 400.
107
What triggers completion of meiosis II?
Fertilisation by sperm.
108
What do granulosa cells do?
Support oocyte and secrete oestrogen.
109
What do theca interna cells produce?
Androgens
110
What is the antrum?
Fluid-filled space in a mature follicle.
111
What is the corpus luteum?
A temporary endocrine gland formed after ovulation that secretes progesterone and oestrogen.
112
What is PCOS?
A condition where multiple immature follicles develop but do not ovulate.
113
What hormone is elevated in PCOS?
Testosterone
114
Name two symptoms of PCOS.
Irregular periods and hirsutism.
115
What is the function of the fallopian tubes?
Transport the oocyte and site of fertilisation.
116
ampulla
In the female reproductive system, the ampulla is a wide, curved section of the fallopian tube where fertilization typically occurs. It's located between the fimbria and the isthmus, serving as the primary site where sperm and egg meet. The ampulla plays a crucial role in gamete transport and the initial stages of embryonic development
117
What epithelium lines the fallopian tubes?
Ciliated simple columnar epithelium.
118
Where does fertilisation usually occur?
In the ampulla of the fallopian tube.
119
What is an ectopic pregnancy?
Implantation of an embryo outside the uterus.
120
What are the three main parts of the uterus?
Fundus, body, and cervix.
121
What are the three layers of the uterine wall?
Perimetrium, myometrium, and endometrium.
122
Which layer of the endometrium is shed during menstruation?
Stratum functionalis.
123
What hormone maintains the endometrium after ovulation?
Progesterone
124
What does retroflexion of the uterus mean?
The uterus is tipped backward instead of forward.
125
What is the role of cervical mucus?
Acts as a barrier to pathogens and regulates sperm entry.
126
What causes most cervical cancers?
HPV infection.
127
What cells are found in the upper and lower cervix?
Columnar (upper) and squamous (lower).
128
What is the vaginal epithelium type?
Stratified squamous epithelium.
129
What is the function of rugae in the vagina?
Allow expansion during intercourse and childbirth.
130
What pH does the vagina typically have?
Acidic
131
What structures are found in the vestibule?
Urethral and vaginal openings, mucous glands
132
What is the clitoris made of?
Erectile tissue (corpora cavernosa).
133
What is the female homolog of the scrotum?
Labia majora.
134
What is the male homolog of the labia minora?
Spongy urethra.
135
What gland in females corresponds to the prostate in males?
Skene’s gland.
136
What hormone triggers ovulation?
LH surge.
137
What does FSH do?
Stimulates follicle development and oestrogen production.
138
What hormone maintains the corpus luteum during early pregnancy?
hCG.
139
What produces progesterone after ovulation?
The corpus luteum.
140
What hormonal feedback does oestrogen have at high levels?
Negative feedback on FSH and LH.
141
What happens during the menstrual phase?
Shedding of the endometrial lining.
142
What hormone is dominant in the follicular phase?
Oestrogen.
143
When does ovulation occur?
Around day 14.
144
What hormone dominates the luteal phase?
Progesterone
145
What causes endometriosis to grow outside the uterus?
Unknown
146
Do women have ovarian stem cells?
Still debated—new research ongoing.
147
What triggers the start of puberty?
Unknown – complex interplay of genes and environment.
148
Why do some embryos implant in ectopic sites?
Mechanism unclear; risk factors include smoking and PID.
149
What is the difference between sensation and perception?
Sensation is the detection of a stimulus and the recognition that an event has occurred. Perception is the interpretation and conscious experience of that stimulus.
150
Can perception change even if the sensory input remains the same?
Yes, perception can change due to context, attention, or interpretation.
151
What is the basic flow of the sensory pathway?
Stimulus → Sensory receptor → Afferent neuron → CNS → Integration/perception
152
What are descending vs ascending pathways?
Descending = goal-directed (top-down), Ascending = stimulus-driven (bottom-up)
153
Name the five types of sensory receptors by modality.
Chemoreceptors, Thermoreceptors, Nociceptors, Mechanoreceptors, Photoreceptors
154
How are sensory receptors classified by distribution?
General senses are widely distributed; special senses are localized to the head.
155
How are sensory receptors classified by origin of stimuli?
Interoceptors (internal), Proprioceptors (position/movement), Exteroceptors (external)
156
What is meant by sensory receptors being “transducers”?
They convert physical/chemical stimuli into receptor potentials via ion channels.
157
How is stimulus intensity encoded?
By the number of activated receptors and the frequency of action potentials.
158
What does the morphology of receptors tell us about specificity?
Free nerve endings = low specificity; receptors synapsing on ganglion cells = high specificity
159
Do all sensory pathways cross to the other side of the brain?
Most do (decussate), except olfactory and gustatory pathways.
160
What is the role of the thalamus in sensory systems?
Acts as a relay station, with specific nuclei for each sense.
161
What is sensory magnification?
Some body parts (e.g., fingers, lips) have overrepresented areas in the cortex due to their sensitivity.
162
Where are olfactory receptors located?
In the olfactory epithelium in the nasal cavity.
163
Do olfactory signals decussate?
No, they stay ipsilateral.
164
Where do olfactory signals project in the brain?
Piriform cortex, entorhinal cortex, and amygdala (involved in memory and emotion).
165
Where are taste receptors located?
In taste buds on the tongue’s papillae.
166
What are the five taste qualities?
Sweet, Sour, Salty, Bitter, Umami
167
What is the pathway of taste information to the brain?
Taste buds → Cranial nerves → Solitary nucleus → Thalamus (VPM) → Gustatory cortex (insula)
168
What photoreceptors are in the retina and what do they detect?
Rods (low light, grayscale), Cones (color, high acuity)
169
What is the primary visual pathway?
Retina → LGN (thalamus) → Primary Visual Cortex (V1)
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What other areas receive visual input?
Superior colliculus (eye movement), Suprachiasmatic nucleus (circadian rhythm)
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What structures amplify sound in the middle ear?
Tympanic membrane and ossicles (malleus, incus, stapes)
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What is the function of the cochlea?
Converts mechanical sound into neural signals via hair cells in the Organ of Corti.
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How does the basilar membrane respond to sound?
Different parts vibrate in response to different frequencies.
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Describe the auditory pathway.
Hair cells → Vestibulocochlear nerve → Brainstem → MGN (thalamus) → Auditory cortex
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What senses linear acceleration and gravity?
Utricle and Saccule using otolith crystals
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What senses rotational acceleration?
Semicircular canals using cupula-bending hair cells
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Where do vestibular signals project?
Spinal cord (posture), Cerebellum (coordination), Colliculus (eye movement), Somatosensory cortex (self-movement)
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What does the CNS use sensory input for?
To create a representation of the external and internal environment.
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Which type of pathway brings sensory input to the brain?
Ascending (afferent) pathways.
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What are descending pathways responsible for in sensory systems?
Goal-directed modulation of sensory processing (e.g., attention, filtering noise).
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What determines the specificity of a sensory receptor?
Its morphology and its connection to ganglion cells.
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What are receptor potentials?
Graded changes in membrane potential generated by stimuli.
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How do receptor potentials lead to action potentials?
If the receptor potential reaches threshold, it triggers APs in connected neurons.
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What is neural coding?
The way neurons encode stimulus intensity and duration through frequency and duration of APs.
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What do chemoreceptors respond to?
Chemical substances (e.g., taste, smell, CO₂ levels).
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What do mechanoreceptors respond to?
Physical deformation (e.g., touch, pressure, sound vibrations).
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What do photoreceptors respond to?
Light (e.g., vision).
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What do thermoreceptors respond to?
Changes in temperature.
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What do nociceptors detect?
Painful or damaging stimuli.
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Where are general sense receptors distributed?
Throughout the body (skin, muscles, joints, viscera).
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Where are special sense receptors located?
In specialized organs in the head (eyes, ears, tongue, nose).
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What do interoceptors monitor?
Internal body conditions (e.g., pH, blood pressure).
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What do proprioceptors monitor?
Position and movement of the body.
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What do exteroceptors detect?
External stimuli such as light, sound, temperature.
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Which two special senses do not relay through the thalamus?
Olfaction (smell) and Gustation (taste).
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What is the function of the thalamus in sensory processing?
It acts as a relay center for sensory information to the cortex.
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What is the role of the sensory cortex?
To interpret sensory information and generate perception.
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What is somatotopy?
The spatial mapping of the body in the somatosensory cortex.
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What kind of neurons are olfactory receptor cells?
Bipolar neurons.
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Where does olfactory processing begin?
In the olfactory bulb’s glomeruli.
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What are mitral cells?
Second-order neurons that relay olfactory information to the cortex.
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Which cranial nerve carries olfactory input?
Cranial Nerve I (Olfactory nerve).
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What is the significance of the olfactory-limbic connection?
Links smell with memory and emotion (via amygdala and hippocampus).
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What structures contain taste buds?
Gustatory papillae on the tongue.
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How many receptor cells are in a single taste bud?
About 50–150.
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What is the function of taste cell microvilli?
Extend into the taste pore and contact dissolved tastants.
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What determines the specificity of a taste receptor cell?
The shape and ion charge of the tastant molecule.
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Which part of the brain integrates taste and smell for flavour perception?
Orbitofrontal cortex.
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What is the photopigment in rods called?
Rhodopsin
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What are the three types of cones and what wavelengths do they detect?
S (short, blue), M (medium, green), L (long, red).
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How do photoreceptors respond to light?
They hyperpolarize (unlike most sensory receptors which depolarize).
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Which retinal cells send action potentials?
Retinal ganglion cells (RGCs).
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Where does the optic nerve partially decussate?
At the optic chiasm.
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What are the subcortical visual targets aside from the primary visual cortex?
Superior colliculus, suprachiasmatic nucleus (SCN).
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What is the function of the ossicles?
Amplify vibrations from the tympanic membrane to the inner ear.
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rods vs cones
Rods are highly sensitive to light and are responsible for vision in dim light and peripheral vision. Cones are responsible for color vision and high visual acuity, particularly in bright light and central vision
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Where are auditory receptors located?
In the Organ of Corti in the cochlea.
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What is the function of stereocilia?
Detect movement and initiate neurotransmitter release.
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What determines which part of the basilar membrane vibrates?
The frequency of the sound.
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What structure relays auditory information to the cortex?
Medial Geniculate Nucleus (MGN) of the thalamus.
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What are otoliths and where are they found?
Calcium carbonate crystals in the utricle and saccule that respond to linear acceleration.
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What is the cupula and where is it found?
A gelatinous structure in the semicircular canals that detects rotational movement.
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Which cranial nerve carries vestibular information?
Vestibulocochlear nerve (Cranial Nerve VIII).
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Where are vestibular signals sent in the brain?
Spinal cord (posture), cerebellum (coordination), superior colliculus (eye movement), somatosensory cortex (self-motion perception).
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What are stem cells?
Cells that divide indefinitely but remain in an undifferentiated state, producing daughter cells that can become specialized.
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What is the Hayflick limit?
The finite number of times a normal cell can divide before dying, discovered by Leonard Hayflick in 1965.
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Do stem cells obey the Hayflick limit?
Many stem cells are not subject to the Hayflick limit and can divide indefinitely.
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Why are stem cells important?
They maintain differentiated cell numbers, replace dead or injured cells, and are essential for tissue renewal.
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What are the 3 types of stem cells based on life stage?
Embryonic, Umbilical, Adult/Child stem cells.
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What are the 4 levels of potency in stem cells?
Totipotent, Pluripotent, Multipotent, Unipotent.
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What does 'potency' mean in stem cell biology?
The potential of a stem cell to differentiate into different cell types.
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What are totipotent stem cells?
Cells that can become any type of cell, including embryonic and extraembryonic tissues (e.g., morula).
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What are pluripotent stem cells?
Cells that can become any tissue of the organism except placenta (e.g., blastocyst).
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What are multipotent stem cells?
Cells that can become multiple types within a specific family (e.g., hematopoietic stem cells).
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What are unipotent stem cells?
Cells that can differentiate into only one specific cell type (e.g., skin stem cells).
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What type of potency do morula cells have?
Totipotent
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What type of potency do blastocyst cells have?
Pluripotent
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What type of potency do umbilical cord stem cells have?
Pluripotent and multipotent.
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What potency do adult/child stem cells have?
Multipotent and unipotent.
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What are ESCs?
Stem cells from the inner cell mass of a blastocyst that can become over 200 cell types
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When were human ESCs first isolated?
1998
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Can we currently control ESC differentiation?
No, not fully.
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What are the sources of embryonic stem cells?
IVF surplus embryos, therapeutic cloning (e.g., somatic cell nuclear transfer).
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What are the ethical concerns of using hESCs?
Debates over when life begins, destruction of embryos, and balancing research benefits with ethical issues.
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What is therapeutic cloning?
A technique using somatic cell nuclear transfer to produce stem cells genetically identical to a patient.
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What was the first UK center to get a therapeutic cloning license?
Newcastle Centre for Life.
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What was the therapeutic aim at the Newcastle Centre for Life?
To create insulin-producing cells for Type 1 diabetes treatment.
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What are umbilical cord stem cells used for?
Treatment of blood cancers (leukemia, lymphoma), immune disorders, and sickle cell disease.
249
Should all parents store cord blood?
There's no strong evidence supporting private storage; public banks (e.g., NHS cord bank) promote altruistic donation.
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What is the potency of adult stem cells?
Multipotent or unipotent.
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Where are adult stem cells found?
In tissues like bone marrow, skin, stomach, and intestinal lining.
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What are hematopoietic stem cells?
Blood-forming stem cells found in bone marrow; can become red or white blood cells.
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Why are adult stem cells hard to identify?
They look similar to surrounding cells and exist in low numbers (~1 in 100,000).
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How do adult stem cells divide?
By symmetrical or asymmetrical division depending on need.
255
What is asymmetrical division?
A process where one daughter cell remains a stem cell, and the other becomes a progenitor cell.
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What influences the fate of a daughter stem cell?
Intrinsic (genetic) and extrinsic (environmental) factors.
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When might stem cells divide symmetrically?
During injury repair when new stem cells are needed to restore tissue.
258
What controls stem cell division and renewal?
Molecular signals, integrins, growth factors, and division rates.
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Why is control of stem cell division important?
Uncontrolled division can lead to cancer; stem cells may become cancer stem cells.
260
What are iPSCs?
Adult cells (usually skin or blood) reprogrammed to an embryonic-like pluripotent state.
261
How are iPSCs created?
By introducing genes (Oct4, Sox2, Klf4, c-Myc) using viruses to reprogram fibroblasts.
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Are iPSCs used in therapy?
Not yet clinically, but widely used in laboratory research.
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What is stimulus-triggered acquisition of pluripotency (STAP)?
A controversial method claiming to induce pluripotency via stress (e.g., acid exposure).
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What happened with STAP cell research?
The 2014 Obokata study was retracted due to scientific misconduct and irreproducibility.
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What was the first clinical use of adult stem cells?
Bone marrow transplants.
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What is leukemia?
A cancer where bone marrow produces abnormal white blood cells.
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What does leukemia treatment involve?
Chemotherapy and/or radiation to destroy diseased cells, followed by bone marrow transplant.
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Why are stem cells needed after chemotherapy or radiation?
To replace the hematopoietic stem cells destroyed during treatment.
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Name 3 types of stem cells and one use for each.
1. Embryonic: Potential for regenerating damaged tissues (e.g., nerve cells).
2. Umbilical: Treating leukemia and other blood disorders.
3. Adult: Bone marrow transplants.
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List stem cell potencies from most to least.
Totipotent → Pluripotent → Multipotent → Unipotent.
271
What is required for the development of new cardiovascular drugs?
Identification of novel targets and a deep understanding of the pathophysiology of the disease.
272
Why are positive inotropic agents associated with side effects?
Because they increase intracellular calcium, which can lead to arrhythmias and cell damage.
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What might be a safer alternative to positive inotropic agents?
Targeting downstream events in cardiac contraction (e.g., calcium sensitizers) to improve contractility without increasing calcium levels.
274
For every 10 people diagnosed with hypertension, how many go undiagnosed?
7 people.
275
What diseases can be caused by untreated high blood pressure?
Stroke, coronary heart disease, chronic kidney disease, and vascular dementia.
276
What are some new vasodilator ligands being studied for hypertension?
Acetylcholine (Ach) and bradykinin.
277
What cell interaction is being targeted for new hypertension therapies?
The interaction between endothelium and vascular smooth muscle cells.
278
What is the dual mechanism of action of Riociguat?
Stimulates sGC in both NO-dependent and -independent manners to enhance cGMP synthesis, causing vasodilation.
279
What conditions is Riociguat used to treat?
Chronic thromboembolic pulmonary hypertension and pulmonary arterial hypertension (PAH).
280
What does aspirin block in the arachidonate pathway?
Cyclooxygenase (COX), preventing conversion of AA to cycloendoperoxides
281
What are key derivatives of the arachidonate pathway in various cells?
- Platelets: Thromboxanes
- Endothelium: Prostacyclin
- Smooth muscle: Prostaglandins
- Leukocytes: Leukotrienes
282
What was the first prostacyclin analog approved for hypertension?
Epoprostenol (IV administration, short half-life).
283
What are advantages of Treprostinil over Epoprostenol?
Longer half-life and can be administered subcutaneously.
284
What is Treprostinil Diethanolamine's current status in the UK?
In Phase III clinical trials.
285
What is Endothelin-1?
The most potent vasoconstrictor ever identified.
286
What type of antagonist is Bosentan?
A non-selective endothelin receptor antagonist (blocks ETa and ETb).
287
Why was Sitaxentan withdrawn?
Due to risk of fatal liver damage.
288
What does Rho-kinase inactivate to increase vascular tone?
MLC phosphatase, increasing phosphorylated MLC.
289
What is the precursor drug to Fasudil?
Azaindole-1.
290
How is Fasudil administered to avoid systemic vasodilation?
By inhalation.
291
What is the role of eNOS in vascular tone?
It produces nitric oxide to maintain normal vascular tone.
292
Name two potential eNOS couplers.
a) Tetrahydrobiopterin (BH4)
b) Cicletanine hydrochloride
293
What effect do potassium channel openers (KCOs) have on vascular smooth muscle?
Hyperpolarize the membrane, reduce calcium entry, and promote relaxation.
294
What is special about Nicorandil?
Acts as both a KCO and an NO donor.
295
What are the clinical uses of Nicorandil?
Angina and arrhythmias.
296
What are the advantages of gene therapy?
Potential for one-time treatment with lifelong effect and full compliance.
297
What are non-viral methods of gene delivery?
Liposomes, naked DNA, electroporation, salt-shock (CaCl₂).
298
What are common viral vectors used in gene therapy?
Adenovirus, AAV, retrovirus, lentivirus, helper-dependent AAV.
299
What makes lentiviruses particularly useful for gene therapy?
Large cassette size and stable transfection.
300
What is a gene target in hypertension gene therapy?
Components of the Renin-Angiotensin System (e.g., angiotensinogen, ACE).
301
What are the main intrinsic factors in cardiac contraction?
Intracellular calcium, ion channel entry, Na+/Ca2+ exchange, SR calcium storage.
302
Why is Digoxin risky?
It has a low therapeutic index and potential for serious side effects.
303
What interactions increase Digoxin plasma concentration?
Amiodarone, verapamil, quinidine.
304
What interaction can increase Digoxin toxicity?
Diuretics (due to hypokalemia).
305
What is Levosimendan’s mechanism of action?
Binds troponin C to increase calcium sensitivity during systole, also acts as PDE inhibitor and K+ channel opener.
306
What is the status of Levosimendan in the UK?
In Phase III trials; licensed in some EU countries.
307
When is Levosimendan used post-cardiac surgery?
At the end of surgery with agreement from cardiac surgeon and anaesthetist.
308
What inflammatory cytokine is elevated in heart failure?
IL-1β (interleukin-1 beta).
309
What does Anakinra do?
Blocks IL-1α and IL-1β signalling, reducing post-MI inflammation and improving heart function.
310
What is Canakinumab and what was shown in the CANTOS trial?
Monoclonal antibody against IL-1β; reduced CV events when administered every 3 months.
311
Why is personalized medicine important in CV disease treatment?
Because current treatments are not equally effective for all patients.
312
What remains a major threat to cardiovascular health?
The rise in type 2 diabetes.
313
What are newer drug classes for type 2 diabetes that help CV health?
DPP-4 inhibitors (gliptins), GLP-1 receptor agonists, SGLT2 inhibitors (flozins).
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