organ phys last chapter

Three major components of the reproductive system

Gonads, internal genitalia, and external genitalia

Germ cells vs gametes vs somatic cells

Germ cells give rise to gametes; gametes are haploid (1n); somatic cells are diploid (2n)

Zygote definition

Diploid cell formed from fusion of two haploid gametes

Functions of the ovary

Gamete production (oogenesis) and hormone secretion (estrogen, progesterone)

Function of fallopian tubes

Site of fertilization and transport of embryo via cilia and smooth muscle

Effect of impaired fallopian tube cilia

Increased risk of ectopic pregnancy due to failed embryo transport

Layers of the uterus

Endometrium (implantation), myometrium (contraction), outer connective tissue (support)

Ovarian reserve

Pool of primordial follicles present at birth

Number of follicles at birth vs ovulated

~1–2 million at birth; ~400 ovulated in lifetime

Stages of folliculogenesis

Primordial → Primary → Secondary → Antral → Preovulatory → Ovulation

Role of granulosa cells

Proliferate, produce estrogen, form follicular fluid

Role of theca cells

Produce androgens for estrogen synthesis

Trigger for ovulation

LH surge induced by high estradiol (positive feedback)

Corpus luteum function

Secretes progesterone to prepare uterus for implantation

Why cycle is 28 days despite long follicle development

Multiple follicle cohorts develop; only one becomes dominant per cycle

Ovarian cycle phases

Follicular → Ovulation → Luteal

Uterine cycle phases

Menses → Proliferative → Secretory

Hormones regulating menstrual cycle

GnRH, FSH, LH, estradiol, progesterone, inhibin

Two-cell two-gonadotropin model

Theca cells (LH) make androgens; granulosa cells (FSH) convert to estrogen

Dominant luteal phase hormone

Progesterone

Cause of menstruation

Drop in progesterone, estrogen, and inhibin due to corpus luteum degeneration

GnRH function

Pulsatile release stimulates FSH and LH secretion

Why GnRH must be pulsatile

Continuous GnRH suppresses FSH/LH release

Cause of LH surge

High estrogen causing positive feedback

Function of inhibin

Inhibits FSH secretion

Mechanism of progestin birth control

Negative feedback suppresses GnRH → ↓FSH/LH → prevents ovulation

Cells producing androgens vs estrogen

Theca cells → androgens; granulosa cells → estrogen

Aromatase function

Converts androgens to estrogen

PCOS characteristics

Anovulation, hyperandrogenism, polycystic ovaries, often insulin resistance

Chromosomal sex determination

Determined by sperm (X or Y chromosome)

Role of SRY gene

Triggers testis development

Development without SRY

Ovaries and female reproductive structures form

Müllerian duct derivatives

Fallopian tubes, uterus, upper vagina

Wolffian duct derivatives

Epididymis, vas deferens, seminal vesicles

Difference between oogenesis and spermatogenesis

Oogenesis finite and cyclical; spermatogenesis continuous

Timing of oocyte formation

Before birth; arrested until puberty

Major hormone classes

Peptide, steroid, amine

Steroid hormone mechanism

Bind intracellular receptors and alter gene transcription

Peptide hormone mechanism

Bind membrane receptors and activate second messengers

Hormonal response to exercise

↑ glucagon, catecholamines, cortisol; ↓ insulin

Why insulin decreases during exercise

Preserves circulating glucose for active tissues

Key trigger of ovulation

LH surge

Hormone maintaining early pregnancy

Progesterone

Most important feature of GnRH

Pulsatile secretion

Functional unit of ovary

Follicle

Most common reproductive disorder

PCOS

What are the types of haploid chromosome pairs?

22 pairs of homologous autosomes; 1 pair of sex chromosomes

What are the types of sex chromosomes?

XX = AFAB; XY = AMAB

How many chromosomes does a diploid cell contain?

46 chromosomes in total

What are some sex chromosomal variances?

Klinefelter (XXY) or Turner (X0) syndromes

What does Sertoli cells do?

Secretes anti-Müllerian hormones which causes regression of Müllerian duct.

What do interstitial cells do?

Secrete testosterone which controls the development of Wolffian ducts and male external genitalia by DHT

Which hormones aid in male development in the fetus?

Testosterone and Anti-Müllerian hormone

What are Primordial Germ Cells (PGC)?

the common origins of spermatozoa and oocytes

How does PGC work?

PGC uses “ameboid” movement from the yolk sac to colonize an area along the dorsal body wall called the genital ridge; the arrival of PGC initiates the formation of bipotential gonads

What happens if the PGC develops into a female?

Gonadal cortex forms ovary, gonadal medulla regresses, Wolfian duct regresses, and Müllerian duct becomes the female genitals

What happens if the PGC develops into a male?

Gonadal cortex regresses, gonadal medulla forms a testis, Wolfian duct forms male genitals, and Müllerian duct regresses

What happens during external genitalia development in females?

Genital tubercule forms clitoris; urethral folds and grooves form labia minors and opening of the vagina and urethra; labioscrotal swellings form labia majora

What happens during external genitalia development in males?

Genital tubercule forms glans penis; urethral folds and grooves form shaft of penis; labioscrotal swellings form shaft of penis and scrotum

What are the germ layers of the embryo?

Endoderm, mesoderm, and ectoderm

What comes from the endoderm?

Digestive system, lungs, and endocrine system

What comes from the mesoderm?

Muscles, skeleton, cardiovascular, reproductive system

What comes from the ectoderm?

Nervous system, reproductive tract, skin and hair

What part of the brain controls hormones?

The pituitary gland

What hormones come from the posterior hypophysis?

Oxytocin and ADH

What hormones come from the anterior hypophysis?

LH, FSH, PRL, GH, TSH, and ACTH

What does Follicle stimulating hormone (FSH) do?

Regulates gametogenesis in gonads

What does Luteinizing hormone do?

controls production of steroid hormones

Which hormones do both sexes produce?

androgen and estrogen

Which sex predominately produces androgen?

Males

Which sex predominately produces estrogen?

Females; progesterone is also dominant in females

What is cryptorchidism?

the failure of both testes to descend

What is thyroid hormone?

Mostly nuclear receptors; long half life

What are catecholamines?

Cell surface receptor; short half life

What are peptide hormones?

Large inactive precursors that are cleaved to inactive prohormones; bind to cell membrane receptors; hydrophilic but cannot freely cross membranes

What are steroid hormones?

Synthesized as needed from cholesterol; NOT STORED; lipophlilic (readily cross membranes); Cytoplasmic/nuclear receptors

What kind of steroid hormone can cross cell membrane?

Only unbound hormones can diffuse into the target cell

How do steroid hormones work?

By altering gene transcription

What are the three main pathways involving hypothalamus and pituitary gland control endocrine system?

Hypothalamic Pituitary Thyroid axis (HPT), Hypothalamic Pituitary Adrenal axis (HPA), Hypothalamic Pituitary Gonadal axis (HPG); operate by negative feedback loops

Where are regularity hormones from?

Released from hypothalamus; acts on anterior pituitary

Where are stimulating hormones from?

Released from anterior pituitary; acts on another endocrine gland

Where are non-tropic hormones from?

Released from an endocrine glad; acts on target cells/tissues

What does prolactin do?

Principally responsible for lactation; concentration increases 20-40x during pregnancy

What does dopamine antagonists do to prolactin?

Increases prolactin secretion

What does dopamine agonists do to prolactin?

MAO inhibitors (block dopamine metabolism) decrease prolactin secretion

What are the effects of thyroid hormone?

Growth and development, calorigenic effects, cardiovascular effects, metabolic effects

What is cretinism?

Failure of thyroid to develop during infancy due to deficiency in iodine