Functions of the Urinary System
Functions include:
1. Storage of urine (nitrogenous waste)
2. Excretion of urine
3. Regulate blood volume
4. Regulate ion balance/acid-base balance.
Kidney Anatomy
Kidneys are bean-shaped organs.
Located in a retroperitoneal position (posterior abdomen) and protected by the floating ribs.
Stabilization and Protection of Kidneys
In addition to ribs, the kidney is protected by adipose tissue and a tough fibrous capsule.
Two layers of adipose:
Perinephric fat (deep; near fibrous capsule)
Paranephric fat (more superficial).
Fibrous capsule (or renal capsule) is outer surface of kidn
Basic Kidney Structure
Renal cortex is outer layer (deep to fibrous capsule). Deep to that is renal medulla.
The concave medial surface is the hilum. Ureter and renal artery/vein enter and exit kidney here.
Extensions of renal cortex between renal medulla are renal columns and
Kidney Blood Supply
Renal arteries branch several times, travel through renal columns to afferent arterioles. The afferent arterioles form a capillary network called glomerulus. Once some blood plasma is filtered, exits via efferent arteriole.
Nephron
- Smallest functional unit of the kidney.
- Produces urine through: 1) filtration, 2) resorption and 3) secretion.
- Millions of nephrons in each renal pyramid.
2 types of nephrons:
Cortical - ~85%
Juxtamedullary - ~ 15%
Juxtamedullary nephrons - very long loops; contribute to ability to concentrate urine.
Nephron has 2 main parts:
1) Glomerulus + Glomerular capsule* = Renal corpuscle (yellow).
2) Renal tubules (blue): contains proximal convoluted tubule, nephron loop (Loop of Henle), distal convoluted tubule, collecting duct.
Renal Corpuscle: Filtration
Renal corpuscle is designed for filtration of blood.
Glomerulus is a capillary bed.
Afferent arterioles bring blood in
Glomerular capsule captures filtrate pushed out of capillaries.
Blood exits out efferent arteriole,
Filtrate (water, salts, waste) trave
Structure of Renal Tubules:
Filtrate enters tubules from the renal corpuscle. Travels through tubule:
1) Proximal convoluted tubule: reabsorption and secretion.
2) Loop of Henle:
Reabsorption of water and solutes.
3) Distal convoluted tubule:
Secretes ions mostly but some reabsorpti
Flow of urine out of kidney
Urine is made in pyramids. The remaining structures just transport the urine to the ureter.
Travels through papilla to minor calyx,
major calyx, renal pelvis and to ureter.
Urinary Tract
Transports urine to outside of body. The kidney is not part of the urinary tract.
Includes:
Ureters
Bladder
Urethra
Ureters
Urine exits kidneys via ureters, which are fibromuscular tubes. They are retroperitoneal (behind the parietal peritoneum).
Ureters go from kidney to bladder, located in pelvis.
Urine is transported from the kidney to the bladder by both gravity AND perist
Kidney Stones
A.k.a., Renal calculus.
Minerals filtering through the kidneys accumulate to form crystals.
Identified by location (kidney, ureter or bladder) or by type. More common in men.
Extremely painful.
Related to dehydration, abnormal pH of urine, oversaturation
Urinary Bladder
The bladder is expandable muscular sac that stores and expels urine.
Lies on pelvic floor posterior to pubic symphysis. Trigone, a stationary region that directs urine to urethra is located posteriorly between openings for ureters.
Wall is composed of muc
Urethra
Fibromuscular tube lined with smooth muscle/mucosa - drains urine from bladder.
Thickening of detrusor muscle forms internal urethral sphincter at bladder-urethra junction (involuntary).
External urethral sphincter surrounds urethra with skeletal muscle s
Micturition (urination)
Urination is expulsion of urine from bladder.
Controlled by the brain (pons)
When bladder is distended (full), stretch receptors send signals to pons.
Detrusor muscle is stimulated to contract, squeeze out urine to urethra.
Internal sphincter relaxation i
Perineum
Perineum is diamond-shaped space between thighs, divided into two triangles:
1) Urogenital triangle from the pubic symphysis to the ischial tuberosities. Contains urethral and vaginal orifices.
2) Anal triangle is bound by ischial tuberosities and coccyx.
Sex Organ Terminology
General: genitalia
Primary sex organs: gonads, which produce gametes (eggs or sperm).
Primary male sex organs (gonads): testes. Produce sperm
Primary female sex organs (gonads): ovaries. Produce eggs.
Overall function of reproductive system: produce offsp
External Genitalia
Male external genitalia:
penis + scrotum
Female external genitalia:
vulva (mons pubis, labia, clitoris, structures associated with vestibule).
Clitoris of female is homologous to penis in male, contains erectile tissue including corpora cavernosa.
Labia m
Gonads and Hormones
Gonads function as endocrine glands (produce hormones) that develop and maintain sex organs and influence sexual function.
Ovaries release estrogen and progesterone; testes produce testosterone.
Development
Male and female homologues are structures that developed from same embryological structures.
Sex differentiation begins in utero around week 7. Fully differentiated by week 20.
Homologues
Female:
Labia majora
Labia minora
Glans clitoris
Bulb of vestibule
Corpora cavernosa
Ovaries
Male:
Scrotum
Scrotal midline
Glans penis
Corpus spongiosum
Corpora cavernosa
Testes
Muscles of Pelvic Floor
Bulbospongiosus muscle covers corpus spongiosum (male) and bulb of vestibule (female). Bulb of vestibule ? corpus spongiosum
Ischiocavernosus muscle covers corpora cavernosa (male and female).
Female Reproductive System
The functions of the female reproductive system:
Produce gametes
Support developing embryo and fetus
Ovaries
The ovaries are lateral to the uterus.
Held in place by mesenteries and ligaments, including suspensory ligament and ovarian ligament. All of these structures are within the broad ligament (peritoneum that hangs over uterus).
Suspensory ligament attaches
Uterine Tubes
Also called Fallopian tubes or oviducts. The uterine tubes begin at the infundibulum (receives the egg) and end at the uterus.
Ciliated fimbriae surround infundibulum and help egg to pass into uterine tube/oviduct.
Just medial to infundibulum is expansion
Ovulation and Uterine Tubes
Ovulated egg is released into peritoneal cavity, close to but NOT directly into infundibulum.
Infundibulum bends over ovary and fimbriae sweep ovarian surface. This produces currents in peritoneal fluid that help bring egg into uterine tube.
Cilia and smo
Uterus
Located in pelvic cavity, anterior to rectum. Held in place by broad ligament and round ligament.
Hollow, thick walled, pear-shaped.
Main portion is body. Rounded top is fundus.
Narrow region inferior to body is isthmus.
Neck of uterus is cervix - cervix
Wall of the Uterus
Uterine wall has three layers, from superficial to deep:
perimetrium
myometrium
endometrium.
Perimetrium is outer serous membrane, continuous with broad ligament.
Myometrium is smooth muscle layer - pushes fetus out during childbirth.
Endometrium is linin
Vagina
Thin-walled tube, inferior to uterus, anterior to rectum, posterior to urethra and bladder. Inner wall is stratified squamous epithelium, has acidic environment
Receives penis/semen during intercourse.
Aka birth canal because infant passes through during
Mammary Glands
Pigmented skin around nipple is areola.
Technically part of the integument: modified sweat glands.
Present in males and females (functional only in females).
Divided into lobes and smaller lobules. Lobules have alveoli that produce milk.
Lobules and alveo
Male Pelvis
The testes produce sperm.
Sperm travel through the epididymis, the ductus deferens, the ejaculatory duct and out via the urethra.
Along the way they pass the accessory sex glands: seminal vesicle, the prostate gland and bulbourethral glands.
Scrotum
Testes are housed in scrotum (external sac, outside body cavity), divided into two compartments by a septum. Scrotum helps maintain temperature of testes for sperm development (body temp is too high).
Two structures found in spermatic cord also help with
Spermatic Cord
Spermatic cord = ductus deferens, cremaster muscle, fascia, testicular vessels and nerves.
Extends from scrotum to inguinal canal.
Medial opening = superficial inguinal ring;
Deep inguinal ring is where ductus deferens and testicular
vessels enter abdomen
Testes: Descent
Gubernaculum (fibrous tissue cord) extends from caudal end of developing testes through body wall and into skin of future scrotum.
Testes follow this path towards scrotum.
Spermatic cord (blood vessels, nerves and ductus deferens) follow testes.
Testes
Inside scrotum, each testis is surrounded by a tunica vaginalis.
Deep to tunica vaginalis is fibrous tunica albuginea.
Testes are subdivided into 250-300 lobules containing seminiferous tubules.
Seminiferous tubules converge and sperm travels to rete test
Seminiferous tubules
Located within testes. Seminiferous tubules contain support cells (Sertoli cells) and dividing germ cells (future sperm).
Epididymis
The epididymis is site of sperm maturation and storage: protein secretions nourish sperm and help maturation.
Ejaculation - smooth muscle in walls of epididymis contract, expel sperm into ductus deferens.
Ductus deferens
Ductus deferens (aka vas deferens) transports sperm during ejaculation.
Extends from epididymis into pelvic cavity. It travels through spermatic cord, superior and then posterior to bladder.
Joins duct of seminal gland to form ejaculatory duct, then passe
Urethra (males)
In males, urethra carries both urine and sperm. Three parts:
1. Prostatic urethra, surrounded by prostate
2. Membranous urethra, surrounded by urogenital diaphragm
3. Spongy urethra, located within penis.
Accessory Glands: Prostate and Seminal Vesicles
Seminal vesicles (posterior to bladder) produce portion of seminal fluid. Join with ductus deferens to form ejaculatory duct.
Prostate (inferior to bladder) also produces some of seminal fluid. Holds prostatic urethra.
Secretions from seminal, prostate an
Penis
Penis delivers sperm into the female reproductive tract.
The root of the penis is the base - where it attaches to the pelvis. The body is the free portion.
The glans penis is the enlarged end.
Skin covering penis is loose.
Where it extends around the glan
Erectile Tissues
Penis is composed of erectile tissues. Erectile tissue is spongy connective tissue with vascular spaces.
Corpora cavernosa makes crura found in root, also found in body.
Corpus spongiosum is found in bulb within root of penis, body of penis and the glans.