Exam 4 Reproductive System Male

Sperm

male sex cells

oocytes (egg)

female sex cells

sex cells

1 set of genetic instructions fround on 23 chromosomes

somatic cells

2 sets of 46 chromosomes in other body cells

what happens when sperm and egg unite at ferltization

the genetic information carried on 46 chromosomes is restored.Sex cells are produced by a special type of division called meiosis.

meiosis vs mitosis

Gamete formation involves meiosis, which differs from mitosis

• Involves two consecutive cell divisions (meiosis I and II), but only one round of DNA replication

  • Produces four daughter cells

function of meiosis

Number of chromosomes are cut in half (46 to 23)

Introduces genetic diversity, as all daughter cells are genetically different from original cell

4 phases in meiosis 1

prophase 1

metaphase 1

anaphase 1

telophase 1

prophase 1

Involves synapsis: pairing of homologous chromosomes.

Crossover occurs: exchange of genetic material between homologous chromosomes, to produce chromosomes with genetic information from both parents.

metaphase 1

 Chromosome pairs line up on midline of spindle.

Alignment is random, with respect to maternal or paternal origin.

anaphase 1

Homologous chromosome pairs separate, each replicated member migrating to a different pole.

Each daughter cell receives only 1 replicated member of each chromosome pair; this reduces the chromosome number by half.

telophase 1

Cell divides completely, forming 2 new daughter cells.

meiosis 2 begins after telophase 1 teh division is simualr to mitosis there are 4 phases in meiosis 2

prophase 2

metaphase 2

anaphase 2

telophase 2

prophase

Chromosomes condense and reappear, still replicated.

metaphase 2

replicated chromosomes attach to spindle fibers, along midline.

Anaphase II

Centromeres separate, and chromatids migrate to opposite poles.

telophase 2

Each of 2 cells produced in Meiosis I divides into 2 daughter cells.

each cell entering meiosis could produce

4 gametes; this occurs in sperm, but not in eggs; only 1 egg cell matures, and the others degenerate.

This division ends with each sex cell having 1 set of genetic instructions, or 23 chromosomes, compared to 2 sets (46 chromosomes) in other cells.

male reproductive system functions

To develop and maintain male sex cells (sperm).

To transport sperm and fluids to outside of body.

To synthesize male sex hormones.

Primary sex organs

Gonads: Testes

Produce gametes (sex cells): sperm

Secreted androgens ( male steroid sex hormones)

acessory reprodutive organs

Ducts

Glands

External genitalia

male reprodutive system ducts

• Epididymis

• Ductus ( vas)  deferens

• Ejaculatory ducts

• Urethra

male reprodutive system glands

Seminal gland

• Prostate gland

• Bulbourethral glands

external genitalia

Scrotum, Penis

scrotum

Located outside abdominopelvic cavity

Composed of skin and superficial fascia

scortum contains

paired testes

• 3°C lower than core body temperature ( 35 C and 95 F)

• Lower temperature is necessary for sperm production

• Midline septum divides scrotum into two compartments

cremaster muscles

bands of skeletal muscle that elevate testes

structure of testes two tunics surround each testis

tunica vaginalis

tubica albuginea

tunica vaginalis

outer layer derived from peritouneum

tunica albuginea

inner layer forms fibrous capsule

• Septa divide the testis into ~250 lobules

structure of the testes lobules

Contain one to four seminiferous tubules

Seminiferous Tubules: site of sperm production

spermatogenic cells

sperm-forming cells

interstotal endocrine cells (leydig cells)

secrete testosterne

sustentacular sertoli cells

support and nourish spermatogenic cells

spermatic cord

 encloses nerve fibers, blood vessels, and lymphatic vessels that supply testes

structure of a sperm cell

head

midpeice

flagellum

sperm cell head

Nucleus ~ contains 23 chromosomes 

Acrosome~ which contain an enzyme to digest egg membrane

sperm cell midpeice

contains mitochondria and ATP

sperm flagellum

for motility; requires ATP

where does the sperm leave from

the seminiferous tubules enters the tubular network of the rete testes and moves on to the epididymis

where do male fetus testes orginate fromm

masses of tissue behind the parietal peritoneum, near the kidneys.

Usually 1 – 2 months before birth, testosterone produced by the developing testes triggers their descent into the Scrotum.

gubernaculum

aids the descent through the inguinal canal. (testes)

After descent, spermatic cord contains the ductus deferens, blood vessels, and nerves.

cryptorchidism

is a condition in which the testes are not descended; may result in sterility

Testicular cancer

Rare, but most common cancer in men age  15–35

• Having mumps that lead to orchitis (inflammation
  of testis) could be a risk factor

• Cryptorchidism(undescended testicle)  is most common risk factor

Sign: painless, solid mass in testis

90% cured by surgical removal of testis and
often radiation or chemotherapy

male duct system

Ducts carry sperm from testes to body exterior

• Epididymis

• Ductus (vas) deferens

• Ejaculatory duct

• Urethra

epididymis

• Paired

• Long coiled tube on the posterior surface of each testis

  • Microvilli (stereocilia) absorb testicular fluid and pass nutrients to stored sperm

Sperm complete maturation here 

• Nonmotile sperm enter and pass slowly through (~ 20 days), become motile

• Can be stored for several months

• During ejaculation, epididymis contracts, expelling sperm into ductus deferens

ductus defernens/was deferns

• Paired Muscular tubes, 45 cm long.

• Extends from epididymis into abdominal cavity through inguinal canal, over and down behind the urinary bladder to join the ejaculatory duct

• Smooth muscle in walls propels sperm from epididymis to urethra (persitalsis)

Vasectomy

cutting and ligating ductus deferens

Nearly 100% effective form of birth control

Ejaculatory Ducts

• Paired

• Receive sperm from the ductus deferens and the secretions of the seminal glands

• Pass through the prostate gland

• Empties into urethra

Urethra

Conveys both urine and semen 

(at different times)

prostatic urethra

intermediate part of the urethra membaonous urethra)

spongey urethra

prostatic urethra

surrounded by prostate

intermediate part of the urethra (membranous urethra)

in urogenital diaphram

spongy urethra

runs through penis; opens at external urethral orifice

male accesory glands

seminal glands

• Prostate gland

• Bulbourethral glands

Seminal glands/vesicles

Paired, on the posterior bladder surface

Contains smooth muscle that contracts during ejaculation

Produces viscous alkaline seminal fluid 

Fructose, citric acid, coagulating enzyme (vesiculase), and prostaglandins

Comprises 70% volume of semen

Duct of seminal gland joins ductus deferens to form ejaculatory duct

Prostate Gland

❖Encircles urethra inferior to bladder

• ❖Size of peach pit

• ❖Consists of smooth muscle that contracts during ejaculation

• ❖Secretes milky, slightly acid fluid

  • Contains citrate, enzymes, and prostate-specific antigen (PSA)

  • Plays a role in sperm activation

  • Enters prostatic urethra during ejaculation

  • Makes up one-third of semen volume

 Prostate Gland Functions

As a muscle: propel seminal fluid through the urethra and out of the penis during ejaculation. 

prostate gland functions

• The muscle part of the prostate also acts as a “gate” for the flow of urine. 

• There are two shut-off valves that control urination, one (internal sphincter) at the junction of the bladder and the upper part of the prostate, the other (external sphincter) at the base (apex) of the prostate. 

• Both are required to prevent incontinence . 

• The upper shut-off valve also prevents seminal fluid from “shooting backwards” into the bladder during ejaculation (retrograde ejaculation). 

Prostatitis:

inflammatory disorders

• Bacterial infection; acute and chronic; treated with antibiotics

chronic prostatitis

• also called pelvic pain syndrome
  is most common form; two types:

  • Inflammatory type: urinary tract infection symptoms;  pain in external genitalia and lower back; leukocytes
    in urine

  • Noninflammatory type: same as inflammatory but
    no leukocytes or bacteria in urine

Benign prostatic hyperplasia ( BPH)

May be age-related

Distorts urethra

Treated with surgery, but newer options include:

Using microwaves or drugs to shrink prostate

Balloon compression

Radio-frequency radiation

prostate cancer

Second most common cause of cancer death in males

Digital exam screening, PSA levels

Biopsy if abnormal

Treated with surgery and sometimes radiation, castration, drugs.

In clinical trials: cryosurgery, chemotherapy, ultrasound, proton beam therapy

bulbourethral glands

• Paired; pea sized

• Inferior to prostate gland

• Empties into urethra

• Secretion is alkaline to line the urethra just prior to ejaculation

Semen

Mixture of sperm and accessory gland secretions

• 2–5 ml semen are ejaculated containing 20–150 million sperm/ml

• Alkaline fluid neutralizes acidity of male urethra and female vagina and enhances motility of sperm

characteristics of semen

Prostaglandins; decrease viscosity of mucus in cervix and stimulate reverse peristalsis in uterus

• Hormone called relaxin and other enzymes; enhance sperm motility

• Fructose for ATP production and sperm motility

• Can suppress female immune response

• Antibiotic chemicals destroy some bacteria

• Clotting factors coagulate semen

penis consist of

Root and body/shaft that ends in glans penis

• Prepuce, or foreskin

• Internally, penis made up of spongy urethra and three cylindrical bodies of erectile tissue, spongy network of connective tissue and smooth muscle with vascular spaces

• Corpus spongiosum: 

  • surrounds urethra 

• Corpora cavernosa: 

  • paired dorsal erectile bodies

Erection

Parasympathetic 

The three masses of erectile tissue have blood sinuses

• Sexual stimulation cause CNS activation of parasympathetic neurons, which releases nitric oxide (NO) 

• Smooth muscle relaxes and penile arteries dilate, increasing  blood flow and increasing blood pressure , leading to erection

ejaculation

Sympathetic 

• Ejaculation of semen involves peristalsis of all male ducts and contraction of the prostate gland and pelvic floor

• Propulsion of semen from male duct system

Sympathetic spinal reflex

• Bladder sphincter muscle constricts, preventing expulsion of urine

• Ducts and accessory glands contract and empty their contents

• Bulbospongiosus muscles undergo rapid series of contractions that cause expulsion of semen 

spermatogenesis

in seminiferous tubules

Spermatogonia (stem cells)→ primary spermatocytes →

secondary spermatocytes → spermatids → spermatozoa ( sperm)

spermatogensis: summary of events

• Seminiferous tubules

• Epididymis – 20 feet long, 10 to 14 days to travel

• Vas deferens – 18 inches

• Ejaculatory duct

• Urethra

• Total travel time = (64 to 72 days)

The Hypothalamic-Pituitary-Gonadal (HPG) Axis

• Production of gametes and sex hormones is regulated by sequence of hormonal events involving hypothalamus, anterior pituitary gland, and testes 

HPG Axis hormones involves

GnRH, FSH, LH, testosterone, inhibin

• Without GnRH and gonadotropins, testes atrophy, and sperm and testosterone production ceases

• Before birth, male infant has testosterone levels two-thirds of adult

• Soon after birth, levels recede and remain low through childhood until puberty

hypthalmus in HPG AXIS

 releases gonadotropin-releasing hormone (GnRH) 

what does gnrh bind to in HPG Axis

anterior pituitary gondatorophic cells causing them to secrete follicle stomulating hormone, lutenizing homrone, FSH stimulates spermaogenis

LH then bind to what on HPG axis

to interstitial cells, prodding them to secrete testosterone

• Rising testosterone levels trigger spermatogenesis

testosterone role in HPG axis

Testosterone entering the blood stimulates sex organ maturation, development/maintenance of secondary sex characteristics, and libido

rising testoerone levels in HPG axis cause

levels feed back on hypothalamus to inhibit GnRH and on pituitary to inhibit gonadotropin release

inhibin role in HPG

eleased by sustenocytes when sperm count high; inhibits GnRH and FSH release

FSH

Initiates sperm production

LH

stimulates testosterone secretion from the testes

Testosterone

Promotes sperm maturation and secondary sex characteristics.

Inhibin

 Decreases the secretion of FSH to maintain a constant rate of spermatogenesis 

Mechanism and Effects of Testosterone Activity

Testosterone, synthesized from cholesterol, is transformed at some target cells

• Converted to dihydrotestosterone (DHT) in prostate and estradiol in some brain neurons 

• Prompts spermatogenesis and targets all accessory organs

• Has multiple anabolic effects throughout body

• Deficiency leads to atrophy of accessoryorgans, semen volume declines, and erection/ejaculation are impaired; treatment: testosterone replacement