TTU A&P 1 Boros Exam 4

The Urinary System

Kidney-produces urine

Ureter-transports urine toward the urinary bladder

Urinary bladder-temporarily stores urine prior to elimination

Urethra- conducts urine to exterior

Functions of the Kidneys (1)

Excretion:

-removal of waste from body fluids in urine

Regulation of blood:

-ions

control blood NA^+, K^+, and CL^-

-pH

control blood H^+, and HCO3^- levels

-pressure and volume

control blood fluid volume and thus blood pressure

Functions of the Kidneys (2)

Kidneys accomplish this by three processes:

-Filtration of water, ions, nutrients, and waste products from the blood

-Reabsorption of most of the water, ions, and nutrients back into the blood

-Excretion of metabolic wastes into the urine

The kidneys are our heros

"Insensible" water loss is occurring as I speak and your breathe

-we lost water constantly through:

skin, lungs, and digestive system

The kidneys can regulate water volume in our bodies because they can

-concentrate or dilute the urine

The kidneys are responsible for our ability to survive on land without dehydration

The position of the kidneys

The kidneys are

-located on either side of the vertebral column

-partly protected by rib cage

The divisions of the kidney

Renal cortex

outer portion of the kidney

Renal medulla

inner portion of the kidney

-separated into renal pyramids by renal columns

Blood supply to the kidneys

Each kidney receives blood from a renal artery

It branches into many smaller and smaller arteries which

-travel between renal pyramids within the renal columns and

-ultimately deliver blood via arterioles to a capillary network called "glomerulus"

Facts about the blood supply to kidneys

Kidneys receive 20%-25% of total cardiac output

1.2 L of blood flows through kidneys each minute

The entire blood volume is filtered by the kidney 60 time/day

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

(99% of the filtered blood is actually returned to the cardiovascular system)

Kidney histology

The kidney is composed of:

-nephorns

-collecting duct

The kidney contains about 1.25 million "nephrons" (85 miles in combined length)

The nephron

The nephron is 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

-renal tubule

Renal corpuscle (1)

Spherical structure is composed of:

-glomerulus

-Bowman's capsule

-urinary space

Renal corpuscle (2)

-Glomerulus

intertwining network of capillaries

receives blood from the afferent arteriole

blood leaves through the efferent arteriole

Renal corpuscle (3)

Bowman's capsule

-composed of squamous epithelial cells

-sac-like structure surrounds the glomerulus

Urinary space

-Space b/w the inner layer lining of the glomerulus and the outer layer of the capsule

Filtration of fluid from blood into the nephron

Occurs in the renal corpuscle

Blood pressure

-forces water and dissolved substances out of the glomerulus into the urinary space

-produces a protein-free solution called filtrate which is similar to blood

Three layers of filtration

The glomerulus (capillary): endothelial cell layer

Middle connective tissue

Inner lining of the Bowman's capsule: epithelial cell layer

The role of the glomerular endothelial layer

Specifically, there are pores in the endothelial cells lining the glomerular capillaries

-They are small enough that they prevent passage of blood cells into the filtrate

-But they do allow some proteins to get through

Filtration slits retain proteins

The role of the podocyte later of the inner lining of Bowman's capsule (1)

However, the glomerular capillaries are surrounded by epithelial cells "foot cells" called podocytes of the inner lining of Bowman's capsule

-composed of many foot processes called pedicels

The role of the podocyte later of the inner lining of Bowman's capsule (2)

Filtration slits (narrow gaps) between adjacent pedicels of podocyte

-smaller than the pores of the endothelial cells

-They only allow water and dissolved solutes from the blood into the urinary space

Blockade of the middle connective tissue layer induces kidney diseases

The connective tissue layer between the pores and slits can become clogged with "debris"

This leads to kidney disease and to kidney failure

Renal Tubule (1)

A long u-shaped tube extending from the cortex into the medulla and back to the cortex

Renal Tubule (2)

It begins at renal corpuscle

It is composed of the:

-Proximal covuluted tubule (PCT)

-Loop of Henle

-Distal convoluted tubule (DCT)

-It ends at the collecting duct

Composition of the wall of the tubule

The wall of the renal tubule is composed of epithelial cells

-from squamous

-to columnar

-depending on the degree of activity of that portion of the tubule

Return of Filtrate from the nephron back into the blood (1)

Functions of the renal tubule cells:

-reabsorb nutrients from the filtrate

-return them to the blood

Return of Filtrate from the nephron back into the blood (2)

Functions of the renal tubule cells cont.d:

-reabsorb water (90%) from filtrate

-return it to the blood

-what is left in the tubule is excreted in the urine

-filtrate travelling along the tubule composition changes

Peritubular Capillaries and Vasa Recta

The reabsorbed water and solutes returns from teh filtrate in the tubule to the blood via

-peritubular capillaries

-vasa recta

both are branches of the efferent arteriole

they drain blood into the venous system and back to the heart

PCT (Proximal Covoluted Tubule)

The first segment of renal tubule

bulk reabsorption of filtrate occurs here

-60% to 70% of the filtrate is reabsorbed here

epithelial cells have microvilli to increase surface for reabsorption

The loop of henle

Middle segment of the renal tubule

Composed of:

descending limb

-fluid flows "down" into the medulla

ascending limb

-fluid flows "back up" into the cortex

How the loop of henle concentrates urine

-Na^+ and Cl^- are actively pumped out of the ascending limb ( and back into the bloodstream)

-Water follows out of the descending limb ( and back into the bloodstream)

-tubular fluid becomes very concentrated

urea ( most abundant organic waste from amino acid breakdown) is now the main solute left in the tubular fluid, hence "urine"

The DCT (Distal Convoluted Tubule) (1)

Last segment of the renal tubule

Note that the epithelial cells lining the DCT

-are smaller than those of the PCT and do NOT have microvilli

-these cells are less active than the cells of the PCT

-but these cells are more highly specialized than the cells of the PCT

The DCT (Distal Convoluted Tubule) (2)

Further adjustments to the filtrate are made in the DCT

-very selective reabsorption occurs here

in response to hormones

-to regulate blood pressure and volume and blood pH

The juxtaglomerular apparatus

This is the endocrine structure composed of:

-macula densa

specialized epithelial cells in the DCt

-juxtaglomerular (JG) cells

specialized smooth muscle cells of the afferent arteriole

How the DCT regulates blood pressure and volume (1)

If decreased blood pressure is sensed by the JG cells

the JG cells release renin (a hormone)

renin activates angiotensin (another hormone)

How the DCT regulates blood pressure and volume (2)

Angiotensin

-causes vasoconstriction and secretion of aldosterone (mineralocorticoid hormone) by the adrenal cortex

How the DCT regulates blood pressure and volume (3)

Aldosterone causes DCT cells:

-inc. Na^+ reabsorption (water always follows Na^+)

-Both are returned to the blood

-This inc. blood pressure and volume

How the DCT regulates blood pressure and volume (4)

If increased blood pressure or volume is sensed by stretch receptors of the heart walls, the atria of the heart releases Atrial Natriurietic Peptide (ANP hormone) causes dec. in Na^+ and water reabsorption at the DCT so inc. in Na^+ and water excretion into the urine

Results in decrease blood pressure and volume

Summary:

Dec. in blood pressure leads to

-Renin -> Angiotensin-> Aldosterone->

Inc. Na+ and water reabsorption at DCT

Inc. blood volume and therefore pressure

Less water in the urine

Urine becomes more concentrated

Inc. in blood pressure leads to

-ANP->

Dec. Na^+ and water reabsorption at DCT

Dec. blood volume therefore pressure

More water in urine

Urine becomes more dilute

How the DCT regulates blood pH

The DCT controls blood pH by both

-H^+ excretion into the forming urine

-HCO3^- (bicarbonate) production and reabsorption into the blood and also buffers the blood

The collecting duct

Determine the final urine

-composition

-volume

Hypothalamic neurons are stimulated by dec blood pressure or inc blood Na^+/Cl^- concentrations:

-they release ADH (antidiurectic hormone):

causes inc. water reabsorption at the collecting duct

Overview of the functions of the components of the nephron and collecting duct

Renal corpuscle- filtration

PCT- bulk reabsorption

Loop of Henle- concentration

DCT-fine tuning with hormones

Collecting duct-fine tuning with hormones

The collecting system of the kidney

The filtrate continues to pass through the collecting duct where its

-final composition is determined

Collecting ducts converge to empty into a minor calyx, which ends at the renal papilla of each renal pyramid

The renal calyces and pelvis

Minor calyx:

-cup-like structure surrounding each renal pyramid

-collects urine from each renal pyramid

-several join to form a major calyx

Major calyx:

-collects urine from several minor calyx

-joins to form the renal pelvis

Renal pelvis:

-acts as a funnel to drain urine from the kidney to the ureter

Urine, transport, storage, and elimination

Takes place in the urinary tract:

Ureter-transports urine toward the urinary bladder

Urinary bladder- temporarily stores urine prior to elimination

Urethra- conducts urine to exterior

The ureters

muscular tubes (smooth muscle)

-collects urine from renal pelvis

-empties urine into the urinary bladder

pass through bladder wall at an angle

-prevents backflow of urine

flatten

-as the bladder is filled with urine

-and when bladder contracts to void the urine

The urinary bladder

hollow, muscular organ (smooth muscle)

temporary reservoir for urine storage

a full bladder can contain 1 L of urine

Urothelium

AKA transitional epithelium (a type of stratified epithelium)

lines the urinary bladder and ureters

composed of cells that

-are impremeable to water

-can rearrange themselves an spread out as the bladder fills with urine

Male urethra

The male urethra is 7 to 8 inches long

Begins at the inferior pole of the bladder

-passes through the prostate gland and penis

Female urethra

The female urethra is much shorter

-1 to 2 inches long

Therefore, a female is prone to more frequent infections of urinary bladder than is the male

The external urethral sphincter

in both sexes:

-skeletal muscle surrounds the urethra

relaxation permits micturition (urination)

Components of the female reproductive system

Ovaries

Uterine tubes

Uterus

Vagina

External genitalia

-Labia

minora

majora

The ovaries (1)

the ovaries are small, almond-shaped organs

composed of:

-an outer cortex

contains follicles

-an inner medulla

contains blood vessels

Composition of follicle

-a female germ cell

"oocyte", which is surrounded by

-an epithelium layer

the epithelium type and function depends on the development

Ovary Oocyte Production Oogenesis (1)

Begins from oocyte stem cells called "oogonia"

Oogonia undergo mitosis to produce oocytes before birth

-(in spermatogonia, mitosis occurs throughout adult life)

Oogonia "sleep" until puberty

Female has all her oocytes by birth

Primordial follicle

From birth until puberty the ovary contains only primordial follicles

Composition:

-a simple squamous epithelium surrounding

-an oocyte

Primary follicle

At puberty and each month in response to FSH, about 12 primordial follicles mature into primary follicles

Epithelial cells of a primary follicle (now called "granulosa cells")

-enlarge

-divide to form a stratified epithelium

-begin to produce estrogen

Secondary follicle

Primary follicles mature into bigger secondary follicles

Epithelial cells of the secondary follicle

-continue to produce estrogen and

-begin to secrete fluid which accumulates in many small cavities between epithelial cells

Tertiary follicle

Each month, only 1 of the 12 maturing follicles develops into a bigger tertiary follicle

-the rest atrophy and degenerate

small cavities b/w epithelial cells fuse into a single large cavity of fluid called the antrum (can become an inch in diameter)

The oocyte

-bulges into the antrum

-separates from the follicle

-then floats free in atrum

Epithelial cells of a tertiary follicle produce a lot of estrogen, leading to an estrogen surge

Ovulation

The estrogen surge leads to a LH surge

The LH surge leads to:

-Ovulation: the release of oocyte from the follicle

The empty tertiary follicle (only epithelial cells left) is transformed into the corpus luteum

The Corpus Luteum (1)

Corpus luteum (yellow body)

-its epithelial cells start to produce progestrone which prepares uterine lining for pregnancy

Corpus albicans

If fertilization does not occur

-the corpus luteum:

degenerates about 12 days after ovulation

fills with scar tissue

thus becomes the corpus albicans (white body)

Hormonal Regulation of the Ovary

view image

Summary of the hormones stimulating ovarian development

FSH causes:

-follicle maturation

LH causes:

-ovulation

-corpus luteum formation

Summary of the phases of the ovarian cycle

The follicular phase

-Primordial through tertiary follicles

-stimulated by FSH

-Estrogen is the primary sex hormone produced by ovaries during this phase

The luteal phase

-corpus luteum and albicans formation

-associated with LH

-progestrone is the primary sex hormone produced by ovaries during this phase

Summary of the functions of the ovaries

Produce female gametes: oocytes

Secrete female sex hormones

-estrogen

-progestrone

Fun Facts

Several million oogonia are orginally produced

Most die in the fetus

At birth:

-the ovaries contain about 2 million primordial follicles

this is all they will every produce

each containing an oocyte

By puberty:

-the number of follicles drop to about 40,000

By menopause:

-the number has dropped to 500

Probably only about 6-10 oocytes are fertilized and only 1/2 of those results in a new born

This means the safety factor for your existence is in the range of 1,000,000

The uterine tubes (1)

AKA fallopian tubes or oviducts

Hollow, muscular tubes

Transport oocyte from ovary to uterus

-oocyte transport takes 3-4 days

Tubes aren't directly connected to the ovaries

The uterine tubes (2)

Fertilization occurs in the uterine tubes near its entrance into the uterus

Unfertilized oocytes degenerate

Tubal pregnancy

Components and Functions of the uterus

Body

-largest portion of uterus

Cervix ("neck")

-distal end projecting into the vagina

The uterus provides

-protection

-nutrition

-waste removal

for a developing fetus

Three layers of the uterine wall (1)

Perimetrium

-outer layer

epithelium and connective tissue

-continuation of the broad ligament

Myometrium

-middle very thick, smooth muscle layer

-provides the force to move the fetus out of the uterus into the vagina

Three layers of the uterine wall (2)

Endometrium

inner glandular and vascular layer

-support the growing fetus

(becomes mother's portion of the placenta)

-estrogen and progesterone produced from ovary cause the glands and blood vessels of the endometrium to develop and grow each month

-if the oocyte is not fertilized, part of it is sloughed

The uterine cycle

Also called menstrual cycle "Period"

A repeating series of changes in the endometrium

Lasts from 21 to 35 days:

-average 28 days

Responds to hormones of the ovarian cycle

Consists of 3 phases

Menses (1)

the destruction of the superficial layer of the endometrium

results in

-release of blood and tissues

stimulated by decrease in progestrone

Menses (2)

Endometrial sloughing lasts 1-7 days

Sheds 35-50 mL of blood

The deeper portion of the endometrium remains to regrow the superficial portion of the next cycle

The proliferative phase

follows menses

results in

-repair and regulation of the endometrium

stimulated by

-estrogen secreted by the ovarian follicles

The secretory phase (1)

begins at ovulation

results in

-secretion by the glands

-rapid growth of the arteries

stimulated by

-progesterone secreted by the ovarian corpus luteum, persisting as long as corpus luteum does

-prepare for embryo

The secretory phase (2)

In preparation for implantation of the fertilized embryo

-the secretions will provide it nourishment

-the vessels will provide the blood ( and oxygen)

Generally lasts about 12 days if fertilization does not occur

Then the cycle is repeated and menses occurs

Summary of the relationship b/w the uterine cycle and the ovarian cycle

3 phases of uterine cycle

-menstrual phase (menses)

-proliferative phase

both occur during follicular phase of the ovarian cycle

-secretory phase

occurs during luteal phase of the ovarian cycle

The vagina

An elastic, muscular tube

Extends from the cervix to the vestibule

Between the

-urethra

-rectum and anus

Funcitions:

-

for mentrual fluids

for spermatozoa

birth canal

The clitoris

Erectile tissue (a plexus of veins)

The female external genitalia (1)

Labia majora

-contains adipose tissue

-protects inner structures

-covered with pubic hair

Labia minora

- medial to the labia major

-not covered with pubic hair

The female external genitalia (2)

Vestibule

-space between the 2 labia minora

-contains the openings for the:

urethra

vagina

The mammary glands (1)

Lie in pectoral fat pads deep to skin of chest

Composed of lobes

-each containing several secretory lobules

which drain their secretory product (milk) into lactiferous duct

most breast cancer is assoc. with the ducts

The mammary glands (2)

Nipple

-contains the openings of the lactiferous ducts

Areola

-reddish brown skin around each nipple

Secrete milk to nourish an infant (lactation)

-controlled by oxytocin

Female Sexual Response

Parasympathetic activation leads to:

-engorgement of erectile tissue of the clitoris

-increased secretion of mucus glads in the cervix and vestibule

The female orgasm is accompanied by:

-peristaltic contractions of smooth muscle in the uterus and vagina due to sympathetic activation

-rhythmic contractions of skeletal muscles surrounding the clitoris due to somatomotor activiation

Components of the male reproductive system

Testes

produce sperm portion of the semen

Duct system

transport the semen

Glands

produce fluid portion of the semen

External genitalia

penis: release the semen

scrotum

Testes

Testes (male gonads)

-egg shaped structures

-suspended in the scrotum

-contains seminiferous tubules

(1/2 mile of these tightly coiled tubules/each side) where sperm are produced in the walls of the tubules

A section through a sminiferoiu tubule: cytology

Contents of sminiferous tubules:

Spermatogonia

sperm stem cells

Sperm at different stages

Sertoli cells

Leydig cells (interstitial cells)

Spermatogensis: Sperm development

the continuous process of sperm production

-begins at puberty

-continues into old age (past 70)

begins at the outermost cell layer in seminiferous tubules

proceeds towards lumen

sperm are released into the lumen

Steps in spermatogensis

Spermatogonia

-sperm stem cells

-undergo mitosis and become into

Spermatocytes

-undergo meiosis and become into

Spermatids

-undergo physical maturation and become into

Spermatozoa (AKA sperm):

-lose contact with wall of the seminiferous tubule

-enter the lumen (about 9 weeks after it was generated by a spermatogonium)

Physical maturation of a sperm

view image

A mature sperm

Head:

-contains nucleus which carries chromosomes

all other organelles are lost, no energy reserves

must absorb nutrients from the surrounding fluid

-the tip of the head is covered by an acrosomal cap essential for fertilization

Middle piece:

-contains mitochondria to provide energy ATP to move the tail

Tail:

-is the only flagellum in the human body, a whip-like organelle to move the cell

Sertoli cells

-extended from the outer capsule to the lumen

-are supporting cells

Support spermatogensis nurture the developing sperm:

provide nutrients and chemical stimuli for development

phagocytize cytoplasm shed by developing sperm

-stimulated by hormones:

FSH and testosterone

Maintain blood-testis barrier

-formed by tight junctions between sertoli cells

-isolated developing sperm cells from blood and immune system since sperm develop after the immune system

Leydig Cells: Not inside the tubules

in the connective tissue surrounding the seminiferous tubules

stimulated by LH to produce testosterone

-the male sex hormone

Male sex hormone: testosterone

is the most important androgen

has many functions:

-stimulates spermatogenesis (maturation of spermatozoa) but not until puberty

-promotes libido (sexual drive) and related behaviors

-establishes male secondary sex characteristics

distribution of facial hair

increased muscle mass and body size

-maintains the glands and organs of male reproductive tract

Summary

Function of Testes

produce male gametes: sperm

produce male sex hormone: testosterone

Semen

Semen= Sperm + fluids

Semen is delivered by the duct system

Along the duct system taken by sperms, fluids are secreted by several exocrine glands

Pathway taken by spermatozoa the duct system: deliver semen to penis

Epididymis

Ductus deferens

Ejaculatory duct

Urethra

prostate gland portion

penis portion

The epididymis

The first part of the duct system next to the testis

a coiled tube almost 7 m long

the primary storage of sperms

-protects sperm

-recycles damaged spermatozoa

sperms leaving the epididymis are still immobile

The ductus deferens

The second part of the duct system begins at the tail of the epididymis about 18 in long

can store sperm for several months:

-in state of suspended animation (low metabolic rates)

contains smooth muscles in its wall, muscular contraction propels semen (sperm and fluid)

travels through the inguinal canal as part of spermatic cord

The spermatic cord

is the name of all of these components that follow the testes, including

-ductus deferens

-nerves

-blood vessels

-and the surrounding layers of the anterior body wall including muscles (e.g cremaster) and connective tissues

The inguinal ligament canal

The inguinal ligament forms inguinal canal

a passageway out the anterior abdominal wall through which the spermatic cord must pass

a weak point in the anterior abdominal wall