Chs 24, 27 Flashcards
Insensible water loss
Water loss through breath and cutaneous transpiration
*water loss we are not conscious of
Sources of water
- metabolism (from dehydration synthesis reactions and aerobic respiration)
- Intake of preformed water
Sensible water loss
- Urine, swearing, etc
* water loss we notice
Obligatory water loss
Water output that is unavoidable
Sodium
- Principal cation of the ECF
- resting membrane potentials – Inflow is essential for depolarization
Potassium
- Principal cation in ICF
- greatest determinant in cellular osmolarity and cell volume
- outflow produces resting membrane potential and action potentials
Chloride
- Most abundant anion of ECF
- Major contributor of osmolarity of ECF
- formation of stomach acid and chloride shift that accompanies CO2 loading/unloading by RBCs
Calcium
- skeletal strength
- activates sliding filament mechanism of muscle contraction
- second messenger of some hormones/neurotransmitters
- stimulates exocytosis of neurotransmitters
- essential in blood clotting
Phosphates
Part of Nucleic acids, ATP, cAMP
Physiological buffers
System that stabilizes pH by controlling body’s output
- urinary system has greatest effect but acts over several hours - respiratory system has smaller effect but acts within minutes
Chemical buffers
Chemical that binds H+ and removes it for solution or releases it into solution as needed
- bicarbonate buffer - phosphate buffer - protein buffer system
Gametes
Sex cells produced by parents that meet and combine to form a zygote (fertilized egg)
Primary sex organs versus Secondary sex organs
Primary - gonads and sex hormones
Secondary - ducts, glands, penis, uterine tubes, uterus, vagina
Secondary sex characteristics
Physique, voice, body hair
Timing of sex differentiation in embryo
Weeks 3-8
- gonads begin to develop at weeks 5-6 beginning as gonadal ridge in medial side of mesonephros (embryonic kidney)
Two ducts of mesonephros
- Mesonephric ducts (Wolffian duct)
- Paramesonephric ducts (Mullerian ducts)
SRY gene and effect on sex differentiation
The Y chromosome contains the SRY gene that stimulates the gonadal ridge to produce testis-determining factor (TDF) to become a testis
- weeks 7-8, the testis produces Mullerian-inhibiting factor to atrophy the Paramesonephric ducts
- if androgen is NOT present, female development occurs at 8-9 weeks
What does it mean to say that external genitalia development arises from homologous structures?
Male and female external genitalia develops from the same embryonic origin
Clitoris – Penis
Greater vestibular glands – bulbourethral glands
Paraurethral glands – prostate glands
Androgen-insensitivity syndrome
- female shows usual signs of puberty but does not menstruate due to presence of testes in the abdomen and XY karyotype
- testes produce androgen but the receptors are insensitive to it
Descent of gonads
Weeks 6-10 - begins
- a connective tissue cord called the gunernaculum extends from the gonad to the floor of the abdominopelvic cavity
- 7th month testes pass through inguinal canal to the scrotum
- inguinal canal is a common site of herniation in males
Cryptorchidism
Undescended testes
Scrotum
Pouch of skin, muscle, and fibrous connective tissue containing the testes
Testes
- Each testis is divided into 250-300 lobules, each containing 1-3 seminiferous tubules that flow into the urete
Seminiferous tubules
Layers of germ cells plus sustentacular cells (aka Sertoli cells) that support and nourish developing germ cells and also form the blood-testis barrier to prevent antibodies from destroying the haploid cells
Spermatic ducts (4 types)
- Efferent ductules - ~12, carry sperm to the epididymis via ciliated cells that move the sperm along
- Duct of epididymis - the epididymis is the site of sperm maturation and storage - remain fertile for 40-60 days
- Ductus deferens - muscular tube that widens into a terminal ampulla - innervated by sympathetic nerve fibers
- Ejaculatory duct - empties into urethra
Accessory glands of the male anatomy (3 sets)
(1) seminal vesicles (constitutes ~60% of semen)
(2) prostate gland (~30% of semen)
(3) bulbourethral gland (produces fluid for lubrication)
Timing of puberty male versus female
10-12 years for male, 8-10 for females
Role of GnRH in Sperm Production
GnRH –> LH –> interstitial cells to secrete androgen
GnRH –> FSH –> Sertoli cells to secrete androgen-binding protein (ABP)
Androgen + ABP = spermatogenesis
Primordial Germ Cell Formation
- the very first blood cells and early reproductive cells are formed by the yolk sac
- the primordial germ cells migrate into the gonadal ridges to become spermatogonia
Three Principal Events of Spermatogenesis
- triggered by rise in testosterone secretion at puberty
- takes place in seminiferous tubules
- three principal events:
(1) division and remodeling of a large germ cell into four small, mobile cells with flagella (mitosis)
(2) reduction of chromosome number by one-half (meiosis)
(3) shuffling of genes so each chromosome of sperm carries new gene combinations (meiosis)
Steps of Spermatogenesis
(1) type A spermatogonium provide lifetime supply of stem cells while type B migrate away from wall (both undergo mitosis)
(2) Type B enlarge to form primary spermatocytes
(3) Primary spermatocytes undergo meiosis I to form haploid secondary spermatocytes
(4) secondary spermatocytes undergo meiosis II to form four spermatids per spermatogonium
(5) spermatids undergo spermiogenesis
Spermiogenesis
Spermatid differentiates into a single spermatozoon - sheds cytoplasm to be left with head (DNA), body (mitochondria), and tail
Sperm count
Semen usually has a sperm count of 50-120 million/mL
Gland contribution to semen
Prostate: calcium, citrate, phosphate, clotting enzyme, protein-hydrolyzing enzyme (serine protease)
Seminal vesicles: fructose, prostaglandins
Fetal egg cells
- during 5th month of pregnancy, fetus carries 6-7 million egg cells
- this drops down to 2 million at birth
- ~400,000 remain at puberty
Uterine wall
- Perimetrium - external Serosa
- Myetrium - smooth muscle
- Endometrium
- site of implantation
- stratum functionalis is shed during menstruation
- stratum basalis regenerates the stratum functionalis
Oogenesis
- release of one egg per month
- primordial germ cells from the yolk sac travel via the gonal ridge to become oogonia before birth
- shortly before birth oogonia transform into primary oocytes (egg or ovum)
- FSH stimulates oocytes to complete meiosis I to produce two daughter cells: a secondary oocyte and a first polar body
- secondary oocytes arrests at metaphase II until after ovulation
- if secondary oocyte is fertilized, it completes meiosis II and sheds a second polar body
Atresia
Degeneration of primary oocytes
First and second polar bodies
First polar body is one of the two daughter cells produced by primary oocytes through meiosis I
- some will go on to meiosis II but ultimately degenerates
Second polar body is shed by a secondary oocyte completing meiosis II
Sexual Cycle
- Ovarian cycle
- Menstrual cycle
Phases of Ovarian Cycle
(1) Follicular phase
- day 1-14 (spans beginning of menstruation to ovulation)
- FSH stimulates development of follicles that secrete estrogen
- LH surges ~day 14 to stimulate ovulation
(2) Ovulation
(3) Luteal phase
- Days 15-28
- corpus luteum develops to secrete progesterone
- degenerates into corpus albicans if no pregnancy occurs
Phases of Menstrual Cycle (Run concurrently with Ovarian Cycle)
(1) Menstrual phase - 5 days
- endometrial discharge
- day 1 of new cycle
(2) Proliferative phase 6-14
- estrogen stimulates regrowth of stratum functionalis and progesterone receptors
(3) Secretory phase - 15-26
- progesterone stimulates uterine glands to secrete glycogen-rich fluid in the event of pregnancy
- Lamina propria swells
- endometrium prepared for implantation
(4) Premenstrual phase 27-28
- drop in progesterone results in endometrial ischemia
Endometriosis
Endometrial tissue escapes the cervix, enters surrounding organs, and begins to grow
Blood supply to uterus
Uterine artery that branches off the internal iliac artery
Define:
Thelarche
Pubarche
Menarche
Thelarche - development of breasts (estrogens)
Pubarche - development of hair, glands (androgens)
Menarche - first menstrual period
Stages of Labor
(1) Dilation
- cervical dilation/effacement
- water breaking
(2) Expulsion
- crowning
(3) Placental stage
- afterbirth
“Window” of Fertilization
- 48 hours before to 14 hours after ovulation
Capacitation
Process sperm must undergo to be able to penetrate an egg (can take around 10 hours)
Acrosmal reaction
Sperm encountering eggs exocytize the acrosome with hyaluronidase and acrosin
Fast versus Slow Block
Fast block = when egg and sperm bind, Na+ channels depolarize the egg membrane to inhibit further binding by other sperm
Slow block = secretory vesicles respond to Ca++ inflow to push away other sperm
Major stages of prenatal development
(1) Preembryonic stage
(2) Embryonic stage
(3) Fetal stage
Preembryonic stage of Fetal Development
Fertilization –> Embryo (first 16 days)
- Cleavage
Blastomeres –> Morula –> Blastocyst - Implantation
6 days after ovulation - Embryogenesis
Layers of Blastocyst
Trophoblast - outer layer of squamous cells that becomes part of the placenta
- secretes HCG to stimulate corpus luteum to release progesterone and estrogen to suppress menstruation
Embryoblast - inner mass of cells that develops into the embryo
Implantation
Trophoblast separates into two layers:
(1) cytotrophoblast
(2) syncytiotrophoblast
Embryogenesis - primary germ layers
(1) Ectoderm –> epidermis, nerve tissue, lens
(2) Mesoderm –> dermis, muscle, blood, skeleton
(3) Endoderm –> mucosal epithelium of GI tract, respiratory tract
Embryonic Stage of Fetal Development
2 weeks to end of 8th week
- organogenesis
Four Embryonic Membranes
(1) Amnion
- protects from trauma, infection, temperature/pressure changes
- allows for movement and symmetrical growth
(2) Yolk sac
- first blood cells, germ cells, contributes to formation of digestive tract
(3) Allatois
- foundation of umbilical cord and becomes part of urinary bladder
(4) Chorion
- outermost membrane
- forms fetal portion of the placenta
Three forms of Prenatal Nutrition
(1) Uterine milk
(2) Trophoblastic nutrition
(3) Placenta
Fetal Stage of Prenatal Development
9 weeks –> birth
- fetal circulation from 2 umbilical arteries and 1 umbilical vein
Ductus Venosus
Allows circulation to bypass liver
Foramen ovals
Oval opening between right and left atria of heart
Ductus arteriosus
Opening between pulmonary trunk and aorta
Neonatal circulation
Foramen ovale –> fossa Ovalis
Ductus arteriosus –> ligamentum arteriosum
Ductus Venosus –> ligamentum Venosum
