Lecture 3 (reproduction) - Exam 5 Flashcards

Question

Answer 1

bundle of fibrous connective tissue containing the ductus deferens, blood and lymphatic vessels, and testicular nerve

Answer 2

Human testes reside in the scrotum because of its cooler environment * Cannot produce sperm at core body temperature of 37°C * Must be held at about 35°C

Answer 3

* Cremaster: strips of the internal abdominal oblique muscle * Dartos fascia: subcutaneous layer of smooth muscle * Pampiniform plexus: an extensive network of veins from the testes that surrounds the testicular artery and spermatic cord

Answer 4

**Cremaster**: strips of the internal abdominal oblique muscle * In **cold temperatures, contracts** and draws testes upward toward body * In **warm temperatures, relaxes** suspending testes further from body

Answer 5

Dartos fascia: subcutaneous layer of smooth muscle * **Contracts when cold**, wrinkling the scrotum, holding testes against warm body * **Reduces surface area** of the scrotum and heat loss

Answer 6

Pampiniform plexus: an extensive network of veins from the testes that surrounds the testicular artery and spermatic cord * **Countercurrent heat exchanger**—without the pampiniform plexus, warm arterial blood would heat the testis and inhibit sperm production * Removes heat from the descending arterial blood * By the time it reaches the testis, the blood is 1.5° to 2.5°C cooler

Answer 7

Prolonged exposure of the testes to elevated temperature, fever, or thermoregulatory dysfunction can lead to temporary or permanent sterility as a result of a **failure of spermatogenesis, whereas steroidogenesis is unaltered**.

Answer 8

* **Primary**: testes * **Accesories**: i.e., the epididymis, vas deferens, seminal vesicles, ejaculatory duct, prostate, bulbourethral gland, urethra, penis)

Answer 9

* travel to the rete testes and, from there, through the efferent ductules to the **epididymis** * In **epididymis storage, protection, transport, increased motility and maturation of sperm** * Ciliary movement in the efferent ductules, muscle contraction, and the flow of fluid accomplish this **movement of sperm.**

Answer 10

* Corpus cavernosum * Dorsal vein, artery and nerve * Urethra is surrounded by corpus spongiosum

Answer 11

* nitric oxide (NO) is derived from the nerve terminals innervating the corpora cavernosa, the endothelial lining of penile arteries, and cavernosal sinuses * Causes smooth muscle relaxation-> penile erection

Answer 12

is expelled by a neuromuscular reflex that is divided into two sequential phases: **(1) emission and (2) ejaculation**

Answer 13

* **Seminal emission** moves the sperm and associated fluids from the cauda epididymis and vas deferens **into the urethra**. * Contraction of the internal bladder sphincter (by α1-adrenergic sympathetic stimulation) **prevents** the ejaculate from traveling up the urethra and into the bladder, known as **retrograde ejaculation**

Answer 14

Ejaculation is the **expulsion of the semen** from the penile urethra; it is initiated after emission.

Answer 15

* Emission: Sympathic * Secretion: Parasympathetic centers * Sensory: pudenal nerve afferents * Expulsion: motor to bulbospongiosus * Spinal ejaculation (rats): lumbar spinothalamics

Answer 16

* semen contains only 10% sperm by volume * remainder secretions of accessory glands * normal volume of semen is 3 mL * 20 to 50 million sperm per mL

Answer 17

* Pair of glands posterior to bladder w sperm * Empties into ejaculatory duct * Forms **75% of semen** * Contains **fructose** (the principal substrate for glycolysis of ejaculated sperm), ascorbic acid, and **prostaglandins** * Responsible for **coagulation** of the semen seconds **after ejaculation**

Answer 18

* Surrounds urethra and ejaculatory duct just inferior to the bladder * 30 to 50 compound tubuloacinar glands * Empty through about 20 pores in the prostatic urethra * **Thin milky secretion** (~0.5 mL) includes fibrinolysin, which is responsible for **liquefaction of coagulated semen** 15-30 minutes **after ejaculation,** releasing sperm.

Answer 19

* Near bulb of penis * During sexual arousal, they produce a clear slippery fluid that **lubricates** the head of the penis in preparation for intercourse (**pre-ejaculatory secretion**) * Protects the sperm by **neutralizing the acidity** of residual urine in the **urethra**

Answer 20

* **Spermatogenesis** produces an abundance of highly specialized, mobile sperm * **spermiogenesis**: maturation of the spermatids into sperm cell

Answer 21

* A spermatogonium becomes a mature spermatozoon after going through several rounds of **mitotic divisions**, a couple of meiotic divisions, and a few weeks of differentiation. * 200 million spermatozoa are produced daily in the adult human testes, which is about the same number of sperm present in a normal ejaculate. * While the **immune system** normally detects and **destroys defective somatic cells**, the blood–testis barrier isolates advanced germ cells from immune surveillance.

Answer 22

Male germ cells, which undergo extensive morphologic changes in cell shape and, ultimately, meiosis to produce the haploid spermatozoa.

Answer 23

Sperm(atozoon) 4 to 5 μm long; structure contains nucleus, acrosome, and tail flagellum

Answer 24

Head: * Nucleus contains **haploid set of chromosomes** * Acrosome—enzyme cap over the apical half of the nucleus that contains enzymes that penetrate the egg **(acrosome reaction)** Tail: * Midpiece contains mitochondria around axoneme of the flagella, produces ATP for flagellar movement

Answer 25

Steroidogenesis

Answer 26

* **Testosterone** main hormone produced by **steroidogenesis** and is primarily secreted by the testes of males and the ovaries of females. * **In males**, testosterone production is about **10 times greater** than that in females and plays a key role in the **development of the testes and prostate** as well as promoting **secondary sexual characteristics**, such as increased hair growth, muscle, and bone mass. It is also essential for health and well-being as well as the **prevention of osteoporosis**

Answer 27

Testosterone is converted to dihydrotestosterone (DHT), the most biologically active androgen, and to estradiol, the most biologically active estrogen (to prevent osteoclast)

Answer 28

Testosterone is primarily synthesized in Leydig cells and is derived from cholesterol, involving many enzymatic steps. * The adrenal cortex, ovaries, testes, and placenta produce steroid hormones from cholesterol. * The major steroid produced by the testis is testosterone, but other androgens, such as androstenediol, androstenedione, and DHEA, as well as a small amount of estradiol, are also produced.

Answer 29

* a substance that stimulates the **growth of the male reproductive tract and the development of male secondary sex characteristics.** * **Anabolic** in nature - have **effects on almost every tissue**, including alteration of the primary sex structures (i.e., the testes and genital tract), stimulation of the secondary sex structures (i.e., accessory glands), and development of secondary sex characteristics responsible for masculine phenotypic expression. * Androgens also affect both sexual and **nonsexual behavior – e.g. aggression.** * relative potency ranking of androgens is as follows: **DHT > testosterone > androstenedione > DHEA**. * Enhanced androgenic activity marks the onset of **puberty**.

Answer 30

* every 28-days * Of the three estrogens (estradiol, estrone, and estriol) estradiol is the most abundant and is many times more potent * Estrogens and androgens in the blood are bound to sex hormone–binding globulin (SHBG) or with lower affinity to albumin

Answer 31

release GnRH in a pulsatile fashion

Answer 32

* GnRH produced by neurons mostly in the **hypothalamic arcuate nucleus** which is released in a pulsatile manner into the hypophyseal portal circulation to **regulate the secretion of LH and FSH** * **Puberty** begins with activation of the gonadotropin-releasing hormone (GnRH) pulse generator within the hypothalamus. * The peptide neurotransmitter **Kisspeptin** stimulates GnRH neurons. * Leptin is among the factors that stimulate Kisspeptin, **especially in females**, to signal adequate metabolic capacity for reproduction.

Answer 33

by an increase in the pulsatile secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which occurs during sleep.

Answer 34

1. **Ovaries**: produce the mature ovum and secrete progestins, androgens, and estrogens 2. **Ductal system**: transports the ovum, is the place of the union of the sperm and egg, and maintains the developing conceptus until delivery

Answer 35

**Oviduct** (fallopian tube): smooth muscle contraction, ciliary movement, and fluid secretion, all of which are under hormonal and neuronal control.

Answer 36

* Each month a single **oocyte** (mature egg) develops and is released from one of the ovaries. * A **follicle** is the functional structure in which this oocyte develops. * Most follicles in the ovary undergo atresia; however, some develop into **mature follicles, produce steroids, and ovulate.** * **As follicles mature, oocytes also mature** by entering meiosis, which produces the proper number of chromosomes in preparation for fertilization. * After rupturing, the follicle becomes a **corpus luteum**

Answer 37

1.**Stratum functionalis (functional layer)** * Changes in response to ovarian hormone cycles * Shed during menstruation 2.**Stratum basalis (basal layer)** * Unresponsive to ovarian hormones * Forms new functionalis after menstruation

Answer 38

* Germs cells (**oogonia**) actively divide by mitosis only during the **prenatal period** * By birth the ovaries contain a **finite number** of oocytes, estimated to be about 1 million. * Most oocytes degenerate and die, a process called **atresia**. * Puberty about 200,000 oocytes; Age 30 about 25,000 remain; Menopause the ovaries are essentially **devoid of oocytes**

Answer 39

* In one of the following **physiologic states**: resting, growing, degenerating, or ready to ovulate. * During each menstrual cycle, the ovaries produce a group of growing follicles, most of which fail to grow to maturity and undergo **follicular atresia**at some stage of development. * However, one **dominant follicle** generally emerges from the cohort of developing follicles and ovulates, releasing a mature haploid ovum.

Answer 40

in a mature graafian follicle.

Answer 41

* acquire receptors for FSH and start producing small amounts of estrogen * The mature graafian follicle contains the oocyte surrounded by granulosa cells and the internal and external theca cell layers.

Answer 42

* Follicular theca cells under the control of luteinizing hormone (LH) * Produce androgens that diffuse to the follicular granulosa cells, where they are converted to estrogens via a follicle- stimulating hormone (FSH)-supported aromatization reaction.

Answer 43

* Androgens are diffused to the granulosa cells, where they are converted to estrogens via a follicle- stimulating hormone (FSH)-supported aromatization reaction * Granulosa cells lack of the enzyme 17α-hydroxylase and **cannot convert** progesterone to androstenedione (indicated by the X)

Answer 44

* Oogonia (2n ovarian stem cells) multiply by mitosis and store nutrients * Primary oocytes develop in primordial follicles * Primary oocytes begin meiosis, but **stall in prophase I** | Think P for primary for P for prophase I

Answer 45

Remain stalled in prophase I

Answer 46

* Ovulation alternates between left and right ovaries * Every month a few primary oocytes are activated * One is selected each month to resume meiosis I (dominant follicle) which result is two haploid cells: **Secondary oocyte + First polar body** * The secondary oocyte ovulated **(arrested in metaphase II)**=> does not complete until fert. * Secondary oocyte gets released from its follicle upon ovulation

Answer 47

* The elevated levels of FSH act on a cohort of follicles recruited 20 to 25 days earlier from the resting pool * During the midfollicular to late follicular phase, **rising estradiol and inhibin** from the dominant follicle **suppress FSH** release **inducing atresia in the nonselected follicles.** * The **dominant follicle** is saved by virtue of its **high density of FSH receptors**, the **accumulation of FSH** in its follicular fluid and the acquisition of LH receptors by the granulosa cells

Answer 48

* **LH surge causes ovulation** * The midcycle surge of LH is short lived (24 to 36 hours) and results from **positive feedback by estradiol.** * The mechanism(s) that transforms estradiol from a negative to a positive regulator of LH to induce the LH surge is incompletely understood. ## Footnote Increase in estrogen (from granulosa cells)-> LH surge-> OVULATION

Answer 49

* As the **corpus luteum matures**, it increases **progesterone production** and reinitiates **estradiol secretion** * After the **demise of the corpus luteum** on days 24 to 26, **estradiol and progesterone levels plunge**, causing the **withdrawal of support of the uterine endometrium**, culminating within 2 to 3 days in **menstruation**.

Answer 50

Ovarian steroids estradiol and progesterone

Answer 51

* Coincides with the mid to late follicular phase of the ovarian cycle. * Under the influence of **rising plasma estradiol concentrations,** the stromal and epithelial layers of the uterine **endometrium** undergo **hyperplasia and hypertrophy**, increasing in size and thickness. * The **endometrial glands elongate** and are lined with columnar epithelium. * The **endometrium becomes vascularized with more spiral arteries** developing to provide a rich blood supply to this region. * Estradiol also induces the expression of **progesterone receptors** and increases myometrial excitability and contractility.

Answer 52

* The **secretory phase** begins on the day of ovulation and coincides with the early to midluteal phase of the ovarian cycle. * Under the combined action of **progesterone and estrogen,** the endometrial glands become coiled, store glycogen (energy source for zygote), and secrete large amounts of carbohydrate-rich mucus. * The stroma **increases in vascularity** and becomes edematous, and the spiral arteries become tortuous * **Peak** secretory activity, edema formation, and overall thickness of the endometrium are reached on days 6 to 8 after ovulation in preparation for implantation of the blastocyst. * Progesterone antagonizes the effect of estrogen on the myometrium to reduce spontaneous myometrial contractions.

Answer 53

* sloughing of entire **functional layer** of endometrium (menses) * begins with **ischemia** in the endometrial tissue initiated by the **declining levels of progesterone and estradiol** that result from **regression of the corpus luteum.** * The **arteries constrict**, reducing the blood supply to the superficial endometrium. * Leukocytes and macrophages invade the stroma and begin to **phagocytose** the ischemic tissue.

Answer 54

* Increased production of **vasoconstrictor prostaglandins** * Prostaglandins induce **vasospasm** of the spiral arteries, and the proteolytic enzymes digest the tissue. * Eventually, the **blood vessels rupture and blood is released,** together with cellular debris. * The endometrial tissue is **expelled** through the cervix and vagina, along with blood from the ruptured arteries.

Answer 55

* The menstrual flow lasts **4 to 5 days** and averages 30 to 50 mL in volume. * The menstrual blood flow **does not clot** due to the presence of fibrinolysin released from the necrotic endometrial tissue.

Answer 56

* is the cessation of ovarian function and reproductive cycles * Defined as 12 months following the completion of her final menstrual period * Usually age 45 – 55.

Answer 57

* The decline in ovarian function is associated with a **decrease in estrogen secretion** and a concomitant **increase in LH and FSH,** which can be used as a diagnostic tool * **Osteoporosis** increases the risk of hip fractures, and estrogen replacement therapy reduces the risk.

Answer 58

* LH: incease * FSH: increase * Estradiol: decrease

Answer 59

Cilia and smooth muscle transport the gametes toward each other within the female genital tract.

Answer 60

Max 3 day window

Answer 61

Fertilization begins as the sperm attaches to the zona pellucida and undergoes the acrosomal reaction

Answer 62

(1) The sperm cell weaves past follicular cells to sperm receptors in the zona pellucida **(sperm-binding)** (2) Intracellular calcium rises in the sperm initiating the **acrosomal reaction**. (3) Proteolytic enzymes released from the acrosome digest the zona pellucida. (4) The sperm penetrates the oolemma, stimulating a rise in intracellular calcium in the egg, which initiates the **cortical reaction (block to polyspermy). ** (5) The rise in intracellular calcium initiates the **completion of the second meiotic division** and generation of the female pronucleus and second polar body. (6) The sperm head enlarges to become the male pronucleus, which **fuses** with the female pronucleus.

Answer 63

* 2 days: 4 cell stage * 3 days: Morula (a solid ball of bastomeres) * 4 days: Early blastocyst (morula hollows out, fills with fluid and hatches from the zona pellucida) * 7 days: Implanting blastocyst (consists of a sphere of trophoblast cells and an eccentric cell cluster called the inner cell mass)

Answer 64

contains the 3 layers: ectoderm, mesoderm and endoderm

Answer 65

**Amnion**: epiblast cells form a transparent sac filled with amniotic fluid * Provides a buoyant environment that protects the embryo

Answer 66

Yolk sac: a sac that hangs from the ventral surface of the embryo * Forms part of the digestive tube * Source of the earliest blood cells, blood vessels, and germ cells

Answer 67

**Allantois**: a small outpocketing at the caudal end of the yolk sac * Structural base for the umbilical cord * Becomes part of the urinary bladder

Answer 68

**Chorion**: helps form the placenta * Encloses the embryonic body and all other membranes * Provides for gas exchange, nutrient exchange

Answer 69

* Maternal portion of placenta (decifua basalis) * Fetal portion of placenta (chorion) * Oxygenated: umbillical vein and Deoxygenated: umbillical arteries

Answer 70

* The intervillous space behaves like a giant capillary, with fresh maternal arterial blood entering from the uterine spiral arteries and leaving via the placental veins * Chorionic villus

Answer 71

The early peak of **chorionic gonadotropin (hCG)** rescues the **corpus luteum**, which is responsible for the early rise in progesterone secretion

Answer 72

Estrogen secretion begins later because maturation of the fetal adrenal glands, which supplies androgen precursors to the placenta, is necessary for estrogen production

Answer 73

Detectable in urine 8 to 9 days after conception by home pregnancy test kits

Answer 74

* Uterus expands, occupies most of abdominal cavity * Lordosis occurs, change in the center of gravity * Weight gain (~ 28 lb) * **Relaxin**: pelvic ligaments & pubic symphysis relax to ease birth passage

Answer 75

hCS is the primary hormone in pregnancy that induces a state of insulin resistance in the mother to promote availability of glucose and fatty acids for the fetus but this increases the risk of developing gestational diabetes mellitus (i.e., the observation of hyperglycemia in a pregnant woman with no prior history of diabetes).

Answer 76

* maturation of the breasts, fetal growth, and glucose sparing in the mother * Human chorionic thyrotropin (hCT) * increase maternal metabolism

Answer 77

* Morning sickness due to elevated levels of estrogen and progesterone * Heartburn and constipation are common * Increase Urine production due to increase metabolism and fetal wastes * Stress incontinence may occur as bladder is compressed

Answer 78

* Estrogens may cause nasal edema and congestion * Tidal volume increases * Dyspnea (difficult breathing) may occur later in pregnancy

Answer 79

* Blood volume increase 25 – 40% * Blood pressure and pulse rise * Venous return from lower limbs may be impaired

Answer 80

* **Suckling inhibits the GnRH** pulse generator, which suppresses FSH and LH release and also suppresses the menstrual cycle in most mothers who are breast-feeding. * Usually **resume menstrual cycles** about 2 months after giving end of breast-feeding.

Answer 81

Residual lung volume, FRC, and TLC (since you need RV)