Anatomy Lecture Exam 4 (URINARY & FEMALE REPRODUCTIVE SYSTEMS)

Components of the Urinary System:

• kidney (produces urine)

• ureter (transports urine to the urinary bladder)

• urinary bladder (stores urine before the urine exits the body)

• urethra (conducts urine to the exterior, lets urine leave your body)

How did urine get its name?

the primary component of urine is uric acid

From Drinking to Urine:

1.) Drinking (liquid is absorbed by the GI tract and transferred to the….)

2.) Blood (the blood circulates to…..)

3.) The Renal Arteries (which supply to….)

4.) Kidneys (which produce….)

5.) Urine 

Reabsorption: 

• when fluid is pulled back into the blood and recirculated

• happens depending on our needs for blood levels 

Function of the Kidneys:

• Excretion

• Blood Regulation

• Filtration

• Reabsorption

• Excrete

Excretion (kidneys):

• removal of waste from the body, in the form of urine

Blood Regulation (kidneys):

Ions

• controls Sodium (Na+), Potassium (K+), and Chlorine (Cl-) levels in the blood

pH

• controls Hydrogen (H+) and Bicarbonate (HCO3-) levels in the blood

Pressure and Volume

• controls blood fluid, therefore controlling blood pressure

Filtration (kidneys):

• filtration of water, ions, nutrients, and waste products from the blood

Reabsorption (kidneys):

• reabsorption of most of the water, ions, and nutrients back into the blood

Excrete (kidneys):

• the metabolic waste in the form of urine

Importance of our Kidneys:

• the kidneys are responsible for maintaining fluid levels in the body

We lose water constantly through everything like:

• skin

• lungs

• digestive system

Our kidneys regulate water by: 

• Concentration

• Dilution

Concentration (kidneys):

• if we need more water to maintain a blood volume then the kidneys will pull more water from the urine and concentrate the urine

Dilution (kidneys):

• if we need to dispose of fluid the kidneys are responsible for diluting the urine and allowing more water to exit out body

Divisions of the Kidney:

Renal Cortex:

• OUTER portion of the kidney

Renal Medulla:

• INNER portion of kidney separated into the RENAL PYRAMIDS by RENAL COLUMNS

Blood Supply to Kidneys:

• each kidney receives blood from a renal artery

• renal artery branches into smaller arteries, that travel between and within renal pyramids and columns

• finally blood is delivered via arterioles to a capillary network called the glomerulus

Kidney Fun Facts:

• kidneys receive 20-25% of cardiac output (per heartbeat a quarter of your blood visits the kidneys)

• 1.2 liters of blood flow through the kidneys every minute

• your entire blood volume is filtered by the kidney 60 times a day

• if the blood filtered by the kidney were entirely excreted, your entire blood volume would be excreted in 25 minutes

• 99% of the filtered blood is returned back to your cardiovascular system

Kidney Histology:

The kidney is composed of the:

Nephron: the functional unit of the kidney , the kidney contains 1.25 nephrons

Collecting System: the tubing that comes after the nephron

The Nephron:

• the functional unit of the kidney

URINE production begins in the nephron

• blood is filtered into the nephron

• composition changes during the process

Composed of:

• renal corpuscle: first portion of the functional unit (the ball)

• renal tubule: follows the renal corpuscle (tubing)

Renal Corpuscle:

Composed of:

1.) Glomerulus

2.) Bowman’s Capsule

3.) Urinary Space

Glomerulus:

• intertwining network of capillaries

• receive blood from the afferent arteriole and leaves through afferent arteriole

Bowman’s Capsule:

• simple squamous epithelial tissue

• create sac like structure surrounding the glomerulus

• encloses the urinary space

Urinary Space:

• space between the inner layer lining of the glomerulus and the outer layer of the capsule

• where the filtrate is pulled off

Filtration from Blood to Nephron:

Occurs in the renal corpuscle

• blood pressure forces liquids and dissolved substances out of the glomerulus and into the urinary space

• produces a protein free solution called filtrate

3 Layers of Filtration:

1.) The glomerulus (capillary): endothelial cell layer

2.) Middle connective tissue layer

3.) Inner lining of Bowman’s capsule: epithelial cell layer

The glomerulus (capillary): endothelial layer

• there are pores in the endothelial cells that line the glomerular capillaries

• main purpose » keep out proteins and red blood cells

• allow SOME proteins to get through 

Middle connective tissue layer:

• can become clogged with “debris” due to being between the pores and slits

• can lead to kidney disease and kidney failure, leading to a kidney transplant

Inner lining of Bowman’s capsule: epithelial cell layer

• “foot cells” called podocytes

• spacing between them is too small to allow proteins to pass

• filtration slits: between pedicles of podocyte

a.) smaller than the endothelial cell pores

b.) only allow H20 and dissolved solutes from the blood into the urinary space, making urine sterile, contaminant free, and protein free

Renal Tubule:

• a long u-shaped tube from the cortex into the medulla and back into the cortex

• begins in the renal corpuscle

Composed of:

• Proximal Convoluted Tubule (PCT) beginning

• Loop of Henle: transgresses into medulla

• Distal Convoluted Tubule: rise back into the cortex 

• ends at the collecting duct

Composition of the tubule wall:

• composed of epithelial cells

• from squamous (thin)

• to columnar

• depending on the degree of activity of the portion of the tubule

Return of Filtrate from Nephron into Blood:

Functions of the renal tubule cells:

• reabsorb nutrients from the filtrate

• return the nutrients back into the blood

• reabsorb 90% of the water from the filtrate

• return the water to the blood

• what is left in the tubule is leaving the body in the form of urine

• filtrate traveling along the tubule, composition changes

Components of the Renal Tubule:

• Proximal Convoluted Tubule (PCT): bulk absorption

• The Loop of Henle: concentrates urine

• Distal Convoluted Tubule (DCT): fine tuning

Proximal Convoluted Tubule (PCT):

• 1st segment of the renal tubule

• bulk reabsorption of the filtrate occurs

• 60-70% of filtrate is reabsorbed here

• epithelial cells have microvilli to increase surface areas for reabsorption

The Loop of Henle:

• middle segment of the renal tubule

Composed of:

• » descending limb: fluid flows down into the medulla & H20 follows out of the descending limb (back into bloodstream)

• » ascending limb: fluid flows back into the cortex & Na+ and Cl- are pumped out of ascending limb (into bloodstream)

• tubular fluid becomes concentrates, “urea” is the main solute left in the tubular fluid

Distal Convoluted Tubule (DCT):

• last segment of the renal tubule

• epithelial cells line the DCT & do not obtain microvilli, less active, more highly specializes

• further adjustments to filtrate and made in the DCT

» selective reabsorption in response to hormones

» regulate the blood pressure, volume, and pH

How DCT regulates blood pH:

• the DCT controls blood pH by both:

» H+ excretion into the forming urine

» HCO3- production and reabsorption into the blood, buffers the blood

The Juxtaglomerular Apparatus:

• endocrine structure is composed of:

» Macula densa: specialized epithelial cells in the DCT

» Juxtaglomerular (JG) cells: specialized smooth muscle cells in the afferent arteriole located in the lining

How DCT regulates blood pressure & volume:

1.) Decreased BP is sensed by JG cells

2.) JG cells release renin (a hormone)

3.) Renin stimulates the release of angiotensin (hormone)

» causes vasoconstriction of the smooth muscle

» stimulates the secretion of aldosterone by the adrenal cortex

4.) Aldosterone

• causes DCT cells

• increases NA+ reabsorption

• H20 and Na+ are returned to the blood

• this increases blood pressure and blood volume

5.) An increase in BP is sense by stretch receptors of the heart walls, the atria of the heart releases Atrial Natriuretic Peptide (ANP)

• ANP causes decrease of Na+ and H2p reabsorption by DCT

• so Na+ and H20 excretion into the urine

• resulting in decreased blood pressure and volume

Collecting Ducts:

The collecting ducts determine the final urine:

• composition

• volume

Hypothalamic neurons are stimulated by:

• decreased blood pressure or increased blood Na+ and Cl- concentration

• the hypothalamus releases ADH, causing increased water reabsorption at the collecting duct

• the collecting ducts converge to empty into a minor calyx, which ends at the renal papilla of each renal pyramids 

Renal Calyces & Pelvis:

• Minor Calyx

• Major Calyx

• Renal Pelvis

Minor Calyx:

• cup-like structure surrounding each renal pyramid

• collects urine from each renal pyramid

• several join to form larger “funnel” shape chambers called major calyx

Major Calyx:

• collects urine from minor calyces

• join and form renal pelvis

Renal Pelvis:

• dumps into the ureter through a funnel like structure

Ureters & Urinary Bladder:

• The ureters

• The Urinary Bladder

• Urothelium

The Ureters: muscular (smooth muscle) tubes

• collect urine from renal pelvis

• empties urine into urinary bladder

• pass through bladder wall at an angle

» prevents back flow

» flatten as the bladder fills

The Urinary Bladder: hollow, muscular organ (smooth muscle)

• temporarily stores urine

• a full bladder can contain 1 liter of urine

Urothelium: transitional epithelium

• lines ureters and urinary bladder

• composed of cells that:

» are impermeable in water

» can rearrange themselves as the bladder fills with urine

Urethras:

Male Urethra:

• 7 to 8 inches long

• begin at the inferior pole of the bladder

• passes through the prostate gland and penis

Female Urethra:

• 1 to 2 inches long

• more prone to more frequent urinary tract infections 

External Urethral Sphincter: in both sexes

• skeletal muscle » surrounds the urethra 

• voluntary muscle » under conscious control for final exit 

• relaxation of this muscle will permit micturition/ urination 

Components of the Female Reproductive System:

Internal:

• ovaries

• uterine tubes (fallopian tubes)

• uterus

• vagina

External

• labia (minora & majora)

The Ovaries:

Composed of:

An outer cortex:

• which also contains the follicles at many different stages, the “egg nest” of the ovary, most of the time only 1 or 2 of them actually mature into eggs

An inner medulla:

• which contains the blood vessels of the ovary which carry the hormones used for ovarian activity 

Also known as the female gonads, female sex organs 

Mitosis:

• where a cell replicates itself: a normal human body cell has 46 chromosomes so in mitosis we have 2 daughter cells each having 46 chromosomes

Meiosis:

• this only occurs in gametes (germ cells). What happens here is the chromosomes get divided in half so gametes contain 23 chromosomes and the fusion of the male and female gametes produces a zygote with 46 chromosomes

Female germ cell:

oocyte

Male germ cell:

spermatozoa

Composition of follicle:

• female germ cell “oocyte” surrounded by an epithelium layer

• the function of the epithelium depends on the stage of development

Oocyte production:

Oogonia: these are the stem cells

• they undergo mitosis and produce oocytes before birth 

• these oocytes are all of the ones a female will ever have and they are produced before birth 

• the oocytes go to bed until puberty (the hormones wake them up) 

Meiosis 1:

• after puberty begins, this occurs at ovulation (the release of an oocyte from the ovary)

• menses

Meiosis 2:

• this only occurs if fertilization happens

The ovarian cycle:

• Primordial follicle

• Primary follicle

• Secondary follicle

• Tertiary follicle

Primordial follicle:

• from birth until puberty the ovary only contains primordial follicles (the sleeping oocytes)

• contents: simple squamous epithelium surrounding an oocyte

Primary follicle:

• each month around 12 primordial follicles mature into primary follicles in response to FSH (follicle stimulating hormone from the anterior pituitary)

» the boundary between oocyte and epithelium gets a bit larger and the epithelium becomes stratified

» estrogen is produced here

Secondary follicle:

• the main difference between primary and secondary is the pockets around the epithelium. These pockets provide the cells with protection and nutrients

» continue to produce estrogen

Tertiary follicle:

• usually 1 of the 12 secondary follicles becomes a tertiary follicle

» what happens is the oocyte pops off the wall and becomes loose in the fluid called the antrum

» by now you have a surge in the hormone estrogen

Ovulation:

• the surge in estrogen leads to a LH (luteinizing hormone also from the anterior pituitary)

• this triggers the release of the oocyte from the follicle (the egg bursts out of follicle)

Corpus luteum:

• means “yellow body” its the aftermath of the burst which is a bunch of epithelial cells

• they produce progesterone (pregnancy hormone)

» prepares the uterine wall for pregnancy by bringing more arterial supply and makes more padding and blood to the uterus for pregnancy

Corpus albicans:

• if fertilization does not occur the corpus luteum degenerates and fills with scar tissue. This is due to a lack of estrogen and progesterone and your body sloughs off the tissue it created in the corpus luteum phase » menses

Internal Female Reproductive parts:

Uterine tubes:

• hollow muscular tubes that transport oocyte from ovary to uterus

• this is where egg fertilization happens through the fertilized egg actually sticks in the uterus

Uterus:

• body, cervix

• the uterus provides protection nutrition and waste removal

Three layers of the uterine wall:

Perimetrium: outer layer that is epithelium and connective tissue

Myometrium: the middle muscle layer (moves fetus out of vagina)

Endometrium: the inner layer, this is the layer that preps for pregnancy

Menses:

• this is the “period” its a release of blood and tissues that is stimulated by the decrease in progesterone

• the uterine cycle that produces menses lasts on average 28 days, actual menses only last 1-7 days

The phases of menses:

• The proliferative phase

• The secretory phase

The proliferative phase:

• follows menses and is the regeneration of the endometrium stimulated by estrogen

The secretory phase:

• begins at ovulation and is where arteries are growing really fast so glands are secreting nutrients

• stimulated by progesterone and lasts as long as the corpus luteum does

Vagina:

• elastic muscular tube between the urethra and the anus

• a passageway for menstrual fluids, spermatozoa, and a birth canal

Vestibule:

• the inner region that houses the labia minora and vagina

Clitoris:

• erectile tissue with a plexus of veins that can engorge similar to the penis

Labia majora (external genitalia):

• protects the inner structures and covered in pubic hair

• adipose tissue

Labia minora (external genitalia):

• medial to the labia majora and are not covered in pubic hair

The mammary glands:

• lie in pectoral fat composed of lobes that secrete milk into lactiferous ducts stimulated by oxytocin

Nipple » opening for the lactiferous duct

Areola » reddish brown skin around each nipple

Female sexual response:

Parasympathetic activation:

• engorgement of clitoris

• increase secretion of mucus glands in the cervix

The female orgasm:

• contractions of the smooth muscle in the uterus and vagina (sympathetic)

• contractions of skeletal muscles around the clitoris