Urinary & Reproductive PP’s(4) A&P2

3 Funct of Urinary System

Excretion

•Removal of organic wastes from body fluids

2. “STORAGE” Elimination

•Discharge of waste products via micturition (URINATION)

3. Homeostatic regulation of the blood

Homeostatic Funct 1

(1)

Regulates blood volume and blood pressure

•Adjusting volume of water lost in urine

•Releasing erythropoietin (RBC) and renin (JUXTAGLOMERULAR COMPLEX)

•Regulates plasma ion concentrations

•Sodium, potassium, and chloride ions (by controlling quantities lost in urine)

•Calcium ion levels (through synthesis of calcitriol—KIDNEYS)

CALCITRIOL INC^ CALCIUM REABSORPTION GI)

PTH>KIDNEY>REABSORB CA+CALCITRIOL

Homeostatic Functions 2

(2)

Helps stabilize blood pH HCO3- takes away hydrogen(acid), acts Base

•By controlling loss of hydrogen ions and bicarbonate ions in urine

•Conserves valuable nutrients (GLUCOSE, AA, FA)

•By preventing excretion while excreting organic waste products

•Assists liver in detoxifying poisons and eliminating wastes

•Nitrogenous wastes (Urea, Uric Acid, Creatinine)—PROTEIN METABOLISM. CREATINE—MUSCLE METABOLISM

•BUN (Blood Urea Nitrogen) measures nitrogenous wastes in blood  

•Azotemia is an elevated BUN —CONCERN FOR KIDNEY FUNCTION

Anatomy of the kidney

Renal Cortex

Renal Pyramids

Renal Columns

Nephrons

Renal Papilla

Major Calyx

Renal Pelvis

Renal Cortex & Pyramids

Renal Cortex FILTRATION OF BLOOD

•Superficial portion of kidney in contact with renal capsule

•Houses majority of nephrons

•Renal Pyramids

•6 to 18 distinct conical or triangular structures in renal medulla

•Base along cortex edge

•Tip (renal papilla) projects into center

Renal Columns & Nephrons

Renal Columns

•Bands of cortical tissue separate adjacent renal pyramids

•Vessels travel through columns to the cortex

•Nephrons

•Microscopic filtering units in cortex

•Where blood is filtered and most urine production occurs

•Consists of microscopic capillaries and tubules

Renal Papilla, Major Calyx, & Pelvis

Renal Papilla

•Papillary duct discharges urine into minor calyx, a cup-shaped drain

•Major Calyx

•Larger cup formed by multiple minor calyces

•Renal Pelvis

•Large, funnel-shaped chamber

•Consists of two or three major calyces

•Connected to ureter, which drains kidney

Blood Supply to the Kidneys

Kidneys receive 20%–25% of total cardiac output

•1200 mL of blood flows through kidneys each minute

•Kidney receives blood through renal artery

The Nephron

Consists of renal tubule and renal corpuscle

Renal Tubule & Corpuscle

•Renal tubule

•Long tubular passageway that begins at renal corpuscle and ends at collecting duct

•Proximal convoluted tubule, loop of henle, and distal convoluted tubule each has distinct function

The Renal Corpuscle

•Each renal corpuscle consists of a capsule and a glomerulus

Glomerulus (Kidney)

•Glomerulus (INSIDE CAPSULE)

•Consists of 50 intertwining capillaries

•Capillaries are fenestrated (contain pores)

•Blood delivered via afferent arteriole

•Blood leaves in efferent arteriole

•Smaller than afferent arteriole

•Provides resistance to increase pressure in glomerulus

Glomerular Capsule

“Bowman’s Capsule”

•Outer wall is lined by simple squamous parietal epithelium

•Continuous with visceral epithelium that covers glomerular capillaries

•Separated by capsular space

•The Visceral Epithelium consists of podocytes

•Complex processes called pedicels wrap around glomerular capillaries

•Filtration Slits are narrow gaps between adjacent pedicels

Glomerular capillaries are…(type)

fenestrated capillaries

•Endothelium contains pores

•The Filtration Membrane

•Consists of:

•Fenestrated endothelium

•Dense layer (basal lamina)

•Filtration slits

Filtration

Blood pressure forces water and small solutes across membrane into capsular space

•Metabolic wastes and excess ions

•Glucose, free fatty acids, amino acids, and vitamins

•Water

•Larger solutes, plasma proteins, blood cells, and platelets remain in the blood

After filtration in Renal Corpuscle…(enters)

filtrate enters the renal tubule

•Three Functions of the Renal Tubule

1.Reabsorb useful organic nutrients and ions that enter filtrate

2.Reabsorb more than 90% of water in filtrate

3.Secrete wastes and excess ions that failed to enter renal corpuscle through filtration at glomerulus

Segments of Renal Tubule

Proximal convoluted tubule (PCT)

•Initial segment

•In cortex

•Distal convoluted tubule (DCT)

•Final segment

•In cortex

•Loop of Henle

•U-shaped tube between the PCT and DCT

•Extends partially into medulla

•Traveling along tubule, filtrate (tubular fluid) gradually changes composition

•Changes vary with activities in each segment of nephron

Each Nephron… (collect)

Empties into the collecting system

•A series of ducts that carry tubular fluid away from nephron

•Collecting ducts

•Receive fluid from many nephrons

•Each collecting duct:

•Begins in cortex and descends into medulla

•Carries fluid to papillary duct that drains into a minor calyx

•Variable reabsorption and secretion of water and some ions still occurs in collecting duct

Cortical & Juxtamedullary Nephrons

Cortical Nephrons

•85% of all nephrons

•Located mostly within superficial cortex of kidney

•Nephron loop (Loop of Henle) is relatively short

•Efferent arteriole delivers blood to a network of peritubular capillaries

•Juxtamedullary Nephrons

•15% of nephrons

•Long nephron loops extend deep into medulla

•Peritubular capillaries connect to vasa recta (long vessels which stretch down around long LOH)

•Allow kidneys to excrete very concentrated urine

Reabsorption + Secretion in Renal Tubule

Tubular Cells

•Absorb organic nutrients, ions, and/or water from tubular fluid

•Release them into peritubular fluid (interstitial fluid around renal tubule)

•Reabsorbed substanaces eventually enter the blood stream via the peritubular capillaries or the vasa recta

Proximal Convoluted Tubule (PCT)

Is the first segment of renal tubule

•Entrance to PCT lies opposite of afferent and efferent arterioles

•Cells have microvilli

•Reabsorption is the primary function (60-70% of filtrate volume reabsorbed)

•Actively reabsorbs 99-100% of organic nutrients

•Active and passive reabsorption of ions

•Passive reabsorption of water via osmosis

•Some secretion occurs

The Nephron Loop (Loop of Henle)

Renal tubule loops down toward/into renal medulla

•Descending limb

•Fluid flows toward renal pelvis  

•Ascending limb

•Fluid flows toward renal cortex

•Each limb contains:

•Thick segment lined with cuboidal cells

•Thin segment lined with squamous cells

The fluid entering the LOH (Kidney)

Does not contain glucose, AA, or other nutrients

•Osmolarity similar to blood

The Descending Limb (K-LOH)

The Descending Limb

•Permeable to water,

•Impermeable to solutes and Ions

•Water follows its osmotic gradient and moves out of descending limb

•Solute concentration (osmolarity) increases as filtrate approaches turn in LOH

The Ascending Limb (K-LOH)

The Ascending Limb

Impermeable to water and solutes

•Active transport of ions out of tubular fluid

•Decreases osmolarity of filtrate leaving the LOH

•Ensures osmolarity outside tubule stays high enough to pull water out of descending limb

•Positive feedback between descending and ascending limb action

Overall in Loop of Henle…(reabsorb)

•Overall in the LOH:

•Active transport reabsorbs 20-25% of sodium and chloride

•Osmosis allows for reabsorption of 25% of water

Distal Convoluted Tubule (DCT)

The third segment of the renal tubule

•Passses between afferent and efferent arteriole

•Cells lack microvilli

•Processes at the DCT

1.Active secretion of acids, drugs, and toxins

2.Selective reabsorption of sodium and excrete K+ by active transport (Regulated by Aldosterone)

3.Selective reabsorption of Calcium (Regulated by PTH & Calcitriol)

4.Selective reabsorption of water

•Concentrates tubular fluid (influenced by ADH)

Control of Urine Volume

Controlled by water reabsorption

•PCT and descending LOH: Water permeable - Osmosis

•Obligatory water reabsorption

•Water movements that cannot be prevented

•Recovers 85% of filtrate volume

•DCT and Collecting System: Relatively impermeable to water

•Facultative water reabsorption

•ADH inserts aquaporins to enhance rate of osmotic movement in DCT and collecting system

The Juxtaglomerular Complex (JGC)

An endocrine structure that secretes:

•Hormone erythropoietin (released when oxygen to kidneys decreases, stimulates erythropoiesis)

•Enzyme renin

•Causes afferent arteriole constriction

•Formed by:

•Macula densa

•Juxtaglomerular cells

Macula Densa (JGC)

Epithelial cells of DCT, near renal corpuscle

•Tall cells with densely clustered nuclei

Juxtaglomerular Cells (JGC)

Smooth muscle fibers in wall of afferent arteriole

•Associated with cells of macula densa

•Together with macula densa forms juxtaglomerular complex (JGC)

Juxtaglomerular Complex (JGC):

of JGC:

Maintaining homeostatic GFR

•Adenosine:

•Released when GFR is too high

•Leads to smooth muscle contraction in afferent arteriole

•Renin:

•Released in response to a decrease in glomerular filtration rate (GFR)

•Converts Angiotensinogen to angiotensin I (ACE converts Angiotensin I to Angiotensin II)

•Angiotensin II increases blood volume and pressure to increase GFR

Transport maximum (Tm) & Renal Threshold

If nutrient concentrations in tubular fluid increase:

•Reabsorption rates increase until carrier proteins are saturated (saturation = Tm)

•Tm determines the renal threshold for that substance

•Blood concentration that correlates with Tm

•Concentration higher than transport maximum:

•Exceeds reabsorptive abilities of nephron

•Some material will remain in the tubular fluid and appear in the urine

Renal Threshold & for Glucose

Renal Threshold

•Is the plasma concentration above which a specific compound begins to appear in urine

•Varies with the substance involved

•Renal Threshold for Glucose

•Is approximately 180 - 220 mg/dL

•If plasma glucose is greater than 180 mg/dL:

•Tm of tubular cells is exceeded

•Glucose appears in urine “Glycosuria” (in diabetes mellitus)

Renal Threshold for Amino Acids

Is lower than glucose (65 mg/dL)

•Amino acids commonly appear in urine

•After a protein-rich meal

•Aminoaciduria

The Process of Glomerular Filtration

Involves passage across a filtration membrane

•Three components of membrane

1.Capillary endothelium

2.Dense layer

3.Filtration slits

Filtration Pressures (Glomerular)

Glomerular filtration is governed by the balance between:

•Hydrostatic pressure (fluid pressure)

•Colloid osmotic pressure (of materials in solution)

Hydrostatic Pressure (Glomerular)

Glomerular hydrostatic pressure is blood pressure in glomerular capillaries

•Tends to push water and solute molecules

•Out of plasma

•Into the filtrate

•Is significantly higher than capillary pressures in systemic circuit due to arrangement of vessels at glomerulus

•Remember smaller efferent arteriole?

•Averages 50 mmHg

Capsular Hydrostatic Pressure (CsHP) (Glomerular)

Opposes glomerular hydrostatic pressure

•Pushes water and solutes

•Out of filtrate

•Into plasma

•Pressure of fluid in capsular space and tubule

•Resistance to flow along nephron tubule and conducting system produce pressure

•Averages about 15 mm Hg

Net Hydrostatic Pressure (NHP) (Glomerular)

Is the difference between:

•Glomerular hydrostatic pressure and capsular hydrostatic pressure

•50-15 = 35mmHg

•Colloid Osmotic Pressure

•Is the osmotic pressure resulting from the presence of suspended proteins

•Blood colloid osmotic pressure (BCOP)

•Results because of plasma proteins that remain in capillaries

•Tends to draw water out of filtrate and into plasma (Opposes filtration)

•Averages 25 mmHg

Net Filtration Pressure (NFP) (Glomerular)

Is the average pressure forcing water and dissolved materials:

•Out of glomerular capillaries

•Into capsular spaces

•At the glomerulus is the difference between:

•Net Hydrostatic pressure and blood colloid osmotic pressure

•35 – 25 = 10 mmHg

The Glomerular Filtration Rate (GFR)

Is the amount of filtrate kidneys produce each minute

•Includes all renal corpuscles

•In both kidneys

•Averages 125 mL/min

•About 10% of fluid delivered to kidneys

•Leaves bloodstream

•Enters capsular spaces

Filtration Pressure (Glomerular)

Glomerular filtration rate depends on filtration pressure

•Any factor that alters filtration pressure alters GFR (Hemorrhage, dehydration, blood pressure changes)

•Control of the GFR

•Three interacting levels of control

1.Autoregulation (local level)

2.Hormonal regulation (initiated by kidneys)

3.Autonomic regulation (by sympathetic division of ANS)

Autoregulation of the GFR

Maintains GFR despite changes in local blood pressure and blood flow

•Reduced blood flow or glomerular blood pressure(reduced GFR) triggers:

•Dilation of afferent arteriole

•Dilation of glomerular capillaries

•Constriction of efferent arterioles

Autoregulation of the GFR (Local)

Local rise in renal blood pressure or flow:

•Stretches walls of afferent arterioles

•Causes smooth muscle cells to contract

•Constricts afferent arterioles

•Decreases glomerular blood flow and pressure

Hormonal Regulation of the GFR

By hormones of the:

•Renin–angiotensin-aldosterone system

•Natriuretic peptides (ANP and BNP)

Renin–Angiotensin-Aldosterone System

Juxtaglomerular complex releases renin due to

•Decline in blood pressure at glomerulus

•decrease in blood volume

•fall in systemic pressures

•Sympathetic Stimulation

•Angiotensinogen – Angiotensin I – Angiotensin II

Angiotensin II

ANGIOTENSIN II:

Constricts efferent arterioles of nephron

•Stimulates reabsorption of sodium ions and water

•Stimulates thirst

•Systemic vasoconstriction

•Stimulates secretion of aldosterone by adrenal cortex

•Reabsorption of sodium and water

•Triggers release of antidiuretic hormone (ADH)

•Stimulates reabsorption of water in distal portion of DCT and collecting system

Hormonal Regulation of GFR (Blood Vol)

Increased Blood Volume

•Automatically increases GFR

•To promote fluid loss

•Hormonal factors further increase GFR

•Accelerating fluid loss in urine

Hormonal Regulation of GFR (NAT Pep)

Natriuretic Peptides

•Are released by the heart in response to stretching walls due to increased blood volume

•Atrial natriuretic peptide (ANP) is released by atria

•Brain natriuretic peptide (BNP) is released by ventricles

•Trigger dilation of afferent arterioles and constriction of efferent arterioles

•Elevate glomerular pressures and increase GFR

•Inhibit NaCl reabsorption

Reabsorption & Secretion (3)

Micturition

•Elimination of urine

•Diuresis

•Is the elimination of large volumes of urine

•Diuretics

•Are drugs that promote water loss in urine

•Diuretic therapy reduces:

•Blood volume

•Blood pressure

•Extracellular fluid volume (edema)

Urine

Urine:

•Results from filtration, absorption, and secretion activities of nephrons

•Organic nutrients are typically completely reabsorbed

•Other compounds (e.g., creatinine, urea) are actively secreted into tubular fluid

•Is a clear, sterile solution, yellow color (urobilin from urobilinogen breakdown)

•Urinalysis, the analysis of a urine sample, is an important diagnostic tool

Urine Transport, Storage, and Elimination

Take place in the urinary tract

•Ureters

•Urinary bladder

•Urethra

The Ureters

Are a pair of muscular tubes

•Extend from kidneys to urinary bladder

•Begin at renal pelvis

•Are retroperitoneal, attached to posterior abdominal wall

•Penetrate posterior wall of the urinary bladder  

•Pass through bladder wall at oblique angle

•Ureteral openings are slit-like rather than rounded

•Shape helps prevent backflow of urine when urinary bladder contracts

Peristaltic Contractions

Begin at renal pelvis

•Sweep along ureter

•Force urine toward urinary bladder

•Every 30 seconds

The Urinary Bladder

Is a hollow, muscular organ

•Functions as temporary reservoir for urine storage

•Full bladder can contain 1 liter of urine

The Bladder Mucosa

Mucosa of the urinary bladder, has folds (rugae) that disappear as bladder fills

The Trigone of the Urinary Bladder

Is a triangular area of thick, smooth mucosa

•Bounded by:

•Openings of ureters

•Entrance to urethra

•Acts as a funnel

•Channels urine from bladder into urethra

The Urethral Entrance

Lies at apex of trigone

•At most inferior point in urinary bladder

The Neck of the Urinary Bladder

Is the region surrounding urethral opening

•Contains a muscular internal urethral sphincter

•Smooth muscle

•Provides involuntary control of urine discharge

The Urethra

Extends from neck of urinary bladder

•To the exterior of the body

The Male Urethra

Extends from neck of urinary bladder to tip of penis (Longer, 7–8 in.)

•Prostatic urethra passes through center of prostate gland

•Membranous urethra includes short segment that penetrates the urogenital diaphragm

•Spongy urethra (penile urethra)extends from urogenital diaphragm to external urethral orifice

The Female Urethra

Is very short (1–2 in.)

•Extends from bladder to vestibule

•External urethral orifice is near anterior wall of vagina

The External Urethral Sphincter

In both sexes

•Is a circular band of skeletal muscle

•Where urethra passes through urogenital diaphragm

•Is under voluntary control

•Has resting muscle tone

•Voluntary relaxation permits micturition (urination)

The Reproductive System

Is the only system that

•Is not essential to the life of the individual

•Has a latent onset

The reproductive organs

•Are involved in the production of offspring by making germ cells called gametes

•Secrete the hormones that maintain normal reproductive function

Male and female reproductive are…

systems are structurally and functionally different

Female

•Produces one gamete per month

•Retains and nurtures zygote, embryo, fetus

•Nourishes infant after birth

Male

•Produces large quantities of gametes (produces 1/2 billion sperm per day)

•Not involved physiologically after sperm is released into vagina

Mitosis VS Meiosis

Mitosis:

•Cell division that occurs in almost all cells in the body

•Daughter cells produced are identical to parent cells

•Body cells have 46 chromosomes total (diploid)

•23 different chromosomes, 2 copies of each per cell

•Meiosis

•Cell division that occurs in sex cells

•Involves 2 stages (meiosis I and meiosis II)

•Produces 4 gametes with half the chromosomes

•Only 23 chromosomes (haploid)

•One copy of each chromosome

•Why is this important?

The Testes

Paired, egg shaped glands

•Hang from body in the scrotum… why?

•Cremaster muscle controls position and temperature

•Septa subdivide testis into smaller lobules

•Lobules contain about 800 slender and  tightly coiled seminiferous tubules

•Site of sperm production “spermatogenesis”

•Small ducts connect the seminiferous tubules to the epididymis

•Coiled duct where sperm go to mature

(Male) Seminiferous tubules

Seminiferous tubules are surrounded by connective tissue capsules

•Slight space between each tubule filled with:

•Areolar tissue

•Blood vessels

•Large interstitial cells (Leydig cells)

•Produce androgens, dominant male sex hormones

•Testosterone is the most important androgen

(Male) Spermatogenesis

•Is the process of sperm production

•Begins at puberty and does not stop with age

•Typical production is 500 million sperm per day

•Begins at outermost cell layer of seminiferous tubules and proceeds inward toward lumen

Spermatogenesis involves…(1)

(1)

Spermatogonia (stem cells) divide by mitosis to produce two daughter cells (____ Chromosomes)

•One remains there as a spermatogonium

•Second differentiates into a primary spermatocyte

Primary spermatocyte undergoes meiosis I and forms 2 secondary spermatocytes

Spermatogenesis involves…(2)

(2)

Secondary spermatocytes undergo meiosis II to produce 4 spermatids (immature gametes) ____ Chromosomes

•Spermiogenesis: The last step of spermatogenesis

•Spermatids become functional sperm cells (spermatozoa)

•4 spermatids are connected (no division of cytoplasm in meiosis I or II)

•Separation and differentiation occur in spermiogenesis

•Spermatozoa lose contact with wall of seminiferous tubule and enter fluid in lumen (spermiation)

Male Seminiferous tubules contain…(Cells)

…various types of cells

•Spermatogonia

•Spermatocytes at various stages of meiosis

•Spermatids

•Spermatozoa

•Large nurse cells (also called sustentacular cells or Sertoli cells)

•Are attached to tubular capsule

•Extend inwards to lumen between other types of cells

Six Major Functions of Nurse Cells

Maintain blood–testis barrier (Male)

•Support mitosis and meiosis

•Support spermiogenesis

•Secrete inhibin

•Secrete androgen-binding protein (ABP)

•Secrete Müllerian-inhibiting factor (MIF)

Maintenance of Blood–Testis Barrier

MAINTENANCE Done by Nurse Cells (Male)

•Nurse cells are joined by tight junctions that create the blood-testis barrier

•Blood-testis barrier isolates inner compartment (luminal compartment) of the seminiferous tubules

•Cells are kept in a protected, tightly regulated environment

•Nurse cells produce and regulate the composition of the luminal fluid

•Blood-testis barrier allows luminal fluid to have very different composition than surrounding interstitial fluid

Nurse Cells Support…(M & M)

…Mitosis and Meiosis (Male)

•Nurse cells are stimulated by:

•Follicle-stimulating hormone, FSH (from _________)

•Testosterone (from ___________)

•Stimulated nurse cells promote:

•Division of spermatogonia

•Division of spermatocytes

Male Support of Spermiogenesis

Nurse cells (Male)

•Surround and enfold spermatids

•Provide nutrients and chemical stimuli needed for development

•Phagocytize cytoplasm shed by developing spermatids

Male Nurse Cells Secrete Inhibin

MALE

•Inhibin

•Is a peptide hormone secreted by nurse cells in response to factors released by sperm

•Depresses:

•Pituitary production of FSH

•Spermatogenesis

•Regulation of FSH and GnRH by inhibin:

•Gives nurse cells negative feedback control of spermatogenesis

•Sperm production, increased inhibin production, decreased FSH, GnRH, decreased sperm

Head & Acrosome Spermatozoa (Male)

Head

•A rounded portion that contains the nucleus and chromosomes

•Acrosome

•A cap-like structure at tip of head

•A membranous compartment that contains enzymes essential to fertilization of the egg

•Made of fused saccules from spermatid’s Golgi apparatus

Middle Piece & Tail Spermatozoa (Male)

Middle piece

◦Attached to head by short neck

◦Contains mitochondria in spiral around microtubules

◦Provides ATP to move tail (flagellum)

◦Tail

◦Is the only flagellum in the human body

◦Is a whiplike organelle that moves cell from one place to another

◦Has complex, corkscrew motion

Sperm Maturation

Testes produce spermatozoa that are physically mature, but not functionally mature

•Spermatozoa in lumen of seminiferous tubule are incapable of locomotion or fertilization

•Are moved into the epididymis by cilia lining the efferent ductules

•Other parts of reproductive system are responsible for functional maturation, nourishment, storage, and transport of spermatozoa

The Epididymis (Male)

The Epididymis

•Is the start of male reproductive tract

•Is a coiled tube almost 7 m (23 ft) long bound to posterior border of testis

•Three Functions of the Epididymis

•Monitors and adjusts fluid produced by seminiferous tubules

•Recycles damaged spermatozoa

•Stores and protects spermatozoa facilitating functional maturation

Spermatozoa leaving Epididymis are…

…are mature, but remain immobile

•To become motile (actively swimming) and fully functional, spermatozoa undergo capacitation

•Two Steps in Capacitation

•Spermatozoa become motile when mixed with secretions of seminal glands

•Spermatozoa become capable of fertilization when exposed to female reproductive tract

The Accessory Glands (Male)

Produce components of semen

•A mixture of secretions from many glands

•Acts as a vehicle for sperm transport

•Important glands include:

•  Seminal glands

•  Prostate gland

•  Bulbo-urethral glands

Semen contains…

…contains

•20 – 100 million sperm per mL

•Seminal fluid

Seminal Fluid

•Transportation medium for sperm

•High concentrations of fructose easily metabolized by spermatozoa (Energy!)

•Prostaglandins stimulate smooth muscle contractions in female to help spread sperm

•Seminogelin forms temporary clot in fluid to keep semen in vagina

•Secreted as proseminogelin, activated by enzymes from prostate

Sperm Motility

Sperm Motility

•Requires alkaline pH

•Spermatic ducts are acidic

•Vagina is acidic

•Upon ejaculation, alkaline secretions from prostate activate motility

•Energy source

•Provided from fructose from seminal vesicles

•Mixing sperm with seminal fluid initiates first step in capacitation

•Spermatozoa begin beating flagella, become highly motile

•“Swim” up the vagina and uterus

Hormones & Male Reproductive Function

Beginning at puberty, the hypothalamus produces Gonadotropin-releasing hormone (GnRH)

•Released in pulses every 60-90 minutes

•Gonadotropin-releasing hormone (GnRH) stimulates theAnterior pituitary gland to release

•Follicle-stimulating hormone (FSH)

•Luteinizing hormone (LH)

FSH, Test, Luteinizing Hormones (Male)

FSH and testosterone

◦Target nurse cells of seminiferous tubules

◦Promote spermatogenesis and spermiogenesis

Luteinizing Hormone

◦Targets Leydig Cells / interstitial cells of testes

◦Induces secretion of:

◦Testosterone

◦Other androgens

Negative Feedback Reg (Male)

Negative Feedback (Male)

•Spermatogenesis is regulated by:

•GnRH, FSH, and inhibin

•GnRH and FSH stimulate spermatogenesis

•As spermatogenesis accelerates, Inhibin secretion increases

•Inhibin selectively inhibits FSH

•Slows spermatogenesis

•Does not decrease production of testosterone (because it does not inhibit release of LH)

Testosterone

Testosterone

•Is the most important androgen

•Stimulates libido (sexual drive) and related behaviors

•Stimulates metabolism

•Establishes male secondary sex characteristics

•Distribution of facial hair

•Increased muscle mass and body size

•Characteristic adipose tissue deposits

•Maintains accessory glands and organs of male reproductive tract

•High testosterone inhibits GnRH release

Female Reproductive System

Produces sex hormones and functional gametes

•Ovaries

•Protects and supports developing embryo

•Uterus

•Nourishes newborn infant

•Breasts

Ovaries

Are small, almond-shaped organs near lateral walls of pelvic cavity

•Three main functions

1.Production of immature female gametes (oocytes)

2.Secretion of female sex hormones (estrogens, progestins)

3.Secretion of inhibin, involved in negative feedback control of pituitary FSH

Oogenesis (Female)

Oogenesis (Female)

•Also called ovum production

•Begins before birth then pauses during fetal development

•Resumes/Accelerates at puberty and continues in a monthly ovarian cycle

•Ends at menopause

Process of Oogenesis

Between third and seventh months: (Female)

•Primary oocytes prepare for and begin meiosis

•Stop at prophase of meiosis I

•Primary oocytes remain in suspended development until puberty

•At puberty:

•Rising FSH triggers start of ovarian cycle

•Each month thereafter, some primary oocytes are stimulated to develop further

Oogenesis: Two Characteristics of Meiosis

(Female)

Cytoplasm of primary oocyte divides unevenly

•Producing one ovum (with original cytoplasm)

•And two or three polar bodies (that disintegrate)

2.Ovary releases secondary oocyte (not mature ovum)

•Suspended in metaphase of meiosis II

•Meiosis is completed upon fertilization

Female reproduction involves 2 cycles

Ovarian Cycle

Uterine Cycle

The Ovarian Cycle

(Female)

Monthly series of events in ovaries that occur during and after the maturation of oocyte

•After puberty, a different group of primordial follicles is activated each month

•Controlled by hormones from the anterior pituitary

•Is divided into:

•Follicular phase (preovulatory phase)

•Luteal phase (postovulatory phase)

The Ovarian Cycle Structures

Ovarian Follicles are specialized structures in cortex of ovaries where oocyte growth and meiosis I occur

•Primary oocytes are located in clusters called egg nests

•Each primary oocyte in an egg nest is surrounded by follicle cells

•Primary oocyte and follicle cells form a primordial follicle

The Uterus

Provides for developing embryo (weeks 1–8) and fetus (week 9 through delivery)

•Mechanical protection

•Nutritional support

•Waste removal

The Uterine Wall

Has a thick, middle, muscular myometrium

•Has a thin, inner, glandular endometrium (mucosa)

•The perimetrium

•Is an Outermost serous membrane continuous with peritoneal lining  

•Covers fundus and posterior surface of uterine body and isthmus

The Myometrium (Female)

(Female)

The Myometrium

•The thickest portion of the uterine wall

•Constitutes almost 90% of the mass of the uterus

•Arranged into longitudinal, circular, and oblique layers

•Provides force to move fetus out of uterus into vagina during birth