A&P 2 Lab Exam 4

Body composition of males compared to females:

Water:

• Males: 60%

• Females 50%

Men have more muscle mass = more water content

What are the electrolytes in body fluids?

ECF (extracellular) ions: Na⁺, Cl^-, HCO₃^-

ICF (intracellular) ions: K⁺, PO₄^3-, Mg⁺

What is the main regulator of water gain?

volume of intake

When are thirst centers in the the hypothalamus stimulated?

when water loss > water gain

What is metabolic water regulated by?

ATP production

What happens when blood volume decreases during dehydration?

Decreased blood volume → decreased blood pressure → baroreceptors in aortic arch and carotid sinus detect low BP → increased sympathetic nervous system activity.

• Acute response: vasoconstriction

• Chronic response: kidneys release more renin → angiotensinogen to angiotensin I → increased angiotensin II (increases thirst and helps body conserve water)

osmolarity

how concentrated blood is

• less water → more concentrated

What happens when osmolarity increases during hydration?

Increased osmolarity → increased osmoreceptors (hypothalamus) → increased antidiuretic hormone release → more water reabsorption in the kidneys (less urine output, more water retention)

What happens when saliva production decreases?

less saliva production → dry mouth → stimulates thirst centers (hypothalamus)

What activates the Renin-Angiotensin-Aldosterone System (RAAS)?

the kidneys detect decreased effective circulating volume (dehydration) and release renin.

What is the RAAS pathway sequence?

• Liver → angiotensinogen

• Kidneys → renin → angiotensin I

• Lungs → Angiotensin-Converting Enzyme (ACE) converts Angiotensin I → Angiotensin II

What does Angiotensin II do?

• stimulates the hypothalamus which increases thirst and increases ADH

• stimulates the adrenal gland which increases aldosterone and causes vasoconstriction

What is the overall effect of RAAs on the kidneys?

• Aldosterone increases Na⁺ reabsorption

• ADH increases water reabsorption

• leads to less Na⁺ and water excretion which increases blood volume

What is the goal of the RAAS system?

restore effective circulating volume by increasing Na⁺ and water retention and thirst.

elimination of excess water and solutes occurs through

urination

Hormonal regulation occurs through renal reabsorption of ___ and ___.

solutes; water

____ and ____ promote reabsorption of Na⁺ and Cl^- and an increase in fluid volume when blood volume is low. The concentration of these hormones decreases when blood volume is high (ie. after a salty meal)

Angiotensin II; aldosterone

_____ promotes natriuresis or increased urinary excretion of Na⁺ and Cl^- which decreases blood volume.

ANP (atrial natriuretic peptide)

• increased BV → increases atrial stretch volume → increased ANP secretion

Secretion of ADH is increased by:

• large decrease in blood volume

• severe dehydration (from drop in blood pressure)

• vomiting, diarrhea, heavy sweating, burns

Secretion of ADH is decreased by:

• water intake

• alcohol intake

Scrotum

• loose skin that houses the testes

• two muscles which assist in temperature regulation of testes:

  • Dartos muscle: contraction causes wrinkling

  • cremaster muscle: contracts/relaxes to adjust distance of testes from body

    • scrotum raises or lowers testes from abdomen

    • reduced temp critical for spermatogensis

Penis

• Consists of 3 cylindrical masses: 2 corpus cavernosum (filled with blood), 1 corpus spongiosum (surrounds urethra and keeps it open during ejaculation)

• Glans: enlarged region at distal end

___% of testes composed of seminiferous tubules.

~80

seminiferous tubules

tightly packed loops containing 4 cell types:

1. Spermatogonia: stem cells (precursors) for sperm

2. Spermatocytes/spermatids: in process of becoming mature sperm

3. Spermatozoa: mature sperm

4. Sertoli cells: provides nutrients for developing sperm

___% of testes composed of leydig cells and connective tissue.

~20

leydig cells

synthesize and secrete male sex hormone testosterone.

Rete Testis

network of small tubes in the testicle that helps move sperm from the testicle to the epididymis.

epididymis

thin, tightly coiled tube located at the posterior surface of the testes

• primary location for sperm maturation and storage

vas deferens

45 cm long muscular tube that connects epididymis to prostate

• propels sperm during ejaculation via peristaltic contractions

• also a site for sperm storage

ejaculatory duct

formed at the junction of the ampulla of vas deferens and seminal vesicles

• enters the prostate gland (located inferior to the bladder)

• passageway to urethra

urethra

carries semen (and urine) prior to exit through penis

• has 3 regions: prostatic, membranous, spongy

How is sperm stored and transported?

1. sperm created in seminiferous tubule

2. emptied into rete testis

3. moves into epididymis

4. travels through vas deferens

5. ejected into ejaculatory duct

6. exit through urethra

How does erection work?

• parasympathetically modulated

• PNS nerves produce and release nitric oxide → vascular smooth muscle dilation

How does ejaculation work?

• sympathetically modulated

• during ejaculation, urinary sphincter of bladder closes

  • failure of sphincter to close causes retrograde ejaculation (sperm goes into bladder instead of out of the penis)

• peristaltic contractions propel semen into urethra

  • at ejaculation, sperm expelled through vas deferens and then urethra

Mons pubis

adipose tissue anterior to pubic bone

Urethra

passageway for urine

clitoris

highly innervated sexual organ above the urethra

labia majora/minora

longitudinal skin folds

• encloses and protects the external structures

lower 2/3 of vagina

intercourse and childbirth

what are the functions of the ovaries?

• produce sex cells (ovum)

  • oogenesis: formation/development of oocytes (eggs)

  • fertilized by sperm

• produce and secrete sex hormones

  • cells responsible for this:

    • theca cells: progesterone

    • granulosa cells: estrogen

fallopian tubes

• 3 regions: infundibulum, ampulla, isthmus

• allows passage ovum from ovaries to uterus

• fertilization occurs in the ampulla

Which part of the fallopian tube connects to the uterus?

isthmus

Which part of the fallopian tube connects to the ovaries?

infundibulum

uterus

• 3 divisions: cervix, body, fundus

• 3 layers

  • perimetrium: outer, thin

  • myometrium: middle thickest

  • endometrium: inner, vascular

• protect and nourish developing embryo and fetus

• menstruation

Ovum Production

1. developing follicles in ovary (born with a certain number of follicles)

2. ejected from ovary (ovulation)

3. fimbriae draw egg in

4. travels through fallopian tube