BIO 202: Chapter 10.1 - 10.6 Male Reproduction

reproductive system

only system in the body that produces new cells genetically different from the rest of the body’s cells

mitosis

process where daughter cells are identical to the parent cell for the purpose of growth, repair, and maintenance of body tissues 

• produces two diploid cells identical to parent cell (46 chromosomes)

prophase

first phase of mitosis in which chromatin condenses into chromosomes, spindle fibers form, and nuclear envelope breaks down

metaphase

second phase of mitosis in which chromosomes align at the cell’s equator, attached to spindle fibers at the centromeres 

anaphase

third phase of mitosis in which sister chromatids separate and move to opposite poles

telophase

fourth phase of mitosis in which chromosomes uncoil into chromatin, nuclear envelopes reform, and cytokinesis completes the division

cytokinesis

final step of cell division in which the cytoplasm splits to create two separate daughter cells 

meiosis

process that reduces the number of chromosomes by half to produce four genetically unique haploid gametes (23 chromosomes)

• meiosis I: separation of homologous chromosomes

• meiosis II: separation of sister chromatids

homologous chromosomes

matching chromosome pairs 

• one from each parent

• same size, shape, and gene sequence but may carry different versions of those genes 

s phase

phase before meiosis I in which DNA replicates to form pair of sister chromatids

prophase I

first phase of meiosis I in which chromatin condenses, homologous chromosomes pair to form tetrads and cross over at chiasmata to exchange DNA, spindle fibers form, and nuclear envelope breaks down

chisamata

points where homologous chromosomes physically connect during meiosis to allow segments of genetic material to be exchanged 

metaphase I

second phase of meiosis I in which tetrads align at the equator

anaphase I

third phase of meiosis I in which homologous chromosomes separate

telophase I and cytokinesis

fourth phase in meiosis I in which two haploid cells form, each with 23 chromosomes 

prophase II 

first phase of meiosis II in which chromosomes condense and spindle fibers reforn

metaphase II

second phase of meiosis II in which chromosome align at the equator 

anaphase II

third phase of meiosis II in which sister chromatids separate to opposite poles

telophase II and cytokinesis 

fourth phase of meiosis II in which four haploid gametes form that each have 23 single-stranded chromosomes 

zygote

fertilized egg that forms when male and female gametes combine 

• has full set of 46 chromosomes 

gonads

primary reproductive organs that produce gametes

• testes in males

• ovaries in females

gametogenesis

process of forming new gametes through meiosis 

external reproductive organs

located in the perineum in both males and females

perineum

diamond shaped area between the thighs in males and females

• bordered by pubic symphysis, coccyx, and left and right ischial tuberosities

• divided into anterior triangle and posterior triangle 

chromatid

one half of a duplicated chromosome

sister chromatids

identical copies joined after DNA replication 

centromere

region where sister chromatids are held together and spindle fibers attach during cell division

short arm (p)

shorter section of the chromosome above the centromere

long arm (q)

longer section of the chromosome below the centromere

telomeres

repetitive DNA sequences at the chromosome ends that protect genetic material

kinetochore

protein structure on the centromere where spindle fibers attach

gene

sequence of deoxyribonucleic acid that contains instructions for making a protein or RNA molecule 

• has a specific locus on a chromosome

alleles

variations of a gene that may produce different traits

scrotum

external sac that houses the testes

• composed of skin, connective tissue, and subcutaneous layer of smooth muscle 

dartos muscle

smooth muscle in the scrotum that contracts in response to cold temperatures to help converse heat

94 F

sperm production requires a temperature of about ____

connective tissue septum

runs along the midline to divide the scrotum into two chambers that each contain one testis

spermatic cord

serves as a passageway for structures that support the testes and passes through the inguinal canal

• deep to scrotum

• layer of connective tissue

inguinal canal

narrow tube about 4 cm long with two openings

• external inguinal ring 

• internal inguinal ring 

external inguinal ring

inferior opening from the scrotum into the inguinal canal

internal inguinal ring

superior opening from the inguinal canal into the pelvic cavity

cremaster muscle

smooth muscle fibers interwoven with the spermatic cord that contract to move the testes closer or farther from the body

• regulate temperature for optimal sperm production

tunica vaginalis

superficial serous membrane producing fluid to reduce friction

• one of the coverings of the testes deep to the cremaster muscle

tunica albuginea

deep, dense connective tissue layer that divides each testis into 250-300 wedge shaped lobules

• one of the coverings of the testes deep to the cremaster muscle

testicular artery

supplies oxygenated blood to the testes

• originates from the abdominal aorta

pampiniform venous plexus

network of slender veins surrounding the testicular artery

• drains deoxygenated blood from the testes

• acts as countercurrent heat exchanger

• lowers arterial blood temperature

testicular vein

after passing through the inguinal canals, the pampiniform venous plexus merge to form this vein

• right drains into inferior vena cava

• left drains into left renal vein

ductus vas deferens

muscular tube that transports sperm from the epididymis toward the ejaculatory duct

• loops posteriorly and superiorly around the urinary bladder

testicular nerves

mixed sensory and motor fibers that innervate the testes

lymphatic vessels

drain excess fluid and help maintain tissue health

testicular torsion

condition in which the spermatic cord can twist and cut off blood supply to the testis

• can cause permanent testicular damage and often requires surgical intervention to untwist and secure the testis

seminiferous tubules

tightly coiled within each testicular lobule

• converge into the rete testis

rete testis

network near the superior portion of the testis that serves as an initial site where sperm cells begin partial maturation

• exits via 12 small efferent ductules

efferent ductules 

contain clusters of ciliated cells that help propel sperm toward the next structure 

epididymis

primary site of sperm maturation and storage

• had three regions (head, body, tail) that immature sperm migrate through to complete maturation before moving into the ductus deferens

vasectomy

surgical method of male contraception in which a short segment of the ductus is cut and sealed

• interrupts the passage of sperm from the epididymis to the urethra so semen no longer contains sperm but other components are still present

ampulla of ductus deferens

widen, enlarged terminal region of the ductus deferens on the posterior surface of the bladder

• serves as a reservoir for sperm

ejaculatory duct

formed by the union of the ampulla of the ductus deferens and the seminal vesicle duct

• passes through the prostate gland and empties into the prostatic urethra

male urethra

prostatic urethra → membranous urethra → spongy urethra

• enters the corpus spongiosum of penis

• terminates at the external urethral orifice at tip of penis

seminiferous tubule → rete testis → efferent ductules → epididymis → ductus deferens → ampulla of ductus vas deferens → ejaculatory duct → urethra → external urethral orifice

pathway of spermatic ducts

seminal vesicles 

paired exocrine glands posterior to the urinary bladder 

• empty into the ejaculatory ducts 

• secretion is rich in fructose to nourish sperm and substances that enhance sperm motility 

prostate gland

single exocrine gland that surrounds the prostatic urethra and ejaculatory ducts

• empties into the prostatic urethra

• thin, milky secretion contains enzymes, citric acid, and antimicrobial agents to help activate and protect sperm

benign prostatic hypertrophy

noncancerous enlargement of the prostate that is common in older men

• can compress the urethra and obstruct urine flow

90%

seminal vesicles and prostate gland together produce about ___ of semen volume which supply nutrients, maintain optimal pH, and help propel sperm

bulbourethral glands

pair of small, brownish glands at the root of the penis

• empty into the membranous urethra 

• secrete alkaline fluid before ejaculation to neutralize acidity

• secrete clear fluid that lubricates head of penis before intercourse

root of penis

internal portion of the penis that anchors it to the pubic arch

glans penis

external portion of the penis

corpus spongiosum

unpaired erectile body of penis that surrounds the spongy urethra and enlarges to form the glans penis

• composed of vascular spaces that fill with blood during erection

corpora cavernosa

paired erectile bodies of penis that are positioned side-by-side along the dorsal aspect of the penis

• composed of vascular spaces that fill with blood during erection

spermatogenesis

process of developing spermatozoa within the seminiferous tubules of the male testis 

• begins at puberty and continues throughout adulthood 

• each cycle takes about 70 days to complete 

testosterone (cells of leydig)

secreted by interstitial cells located between the seminiferous tubules to play key role in regulating spermatogenesis

sustentacular (sertoli) cells 

cells that form the walls of the seminiferous tubules and are connected by tight junctions

• support, nourish, and control movement of developing sperm cells

• remove waste

• produce fluid filling lumen of seminiferous tubules 

blood-testis barrier

formed by the tight junctions of sustentacular cells

• protects developing sperm from harmful substances in the blood

• protects immune system exposure to sperm cell antigens to avoid production of antisperm antibodies

spermatogonium

spermatogonia (stem cell) in outer wall of the seminiferous tubule undergoes mitotic division

• one cell remains a spermatogonium

• other cell becomes primary spermatocyte

primary spermatocyte

diploid with 46 chromosomes enters meiosis

secondary spermatocytes

produced after meiosis I 

• haploid with 23 replicated chromosomes 

spermatids

produced after meiosis II

• haploid with 23 single-stranded chromosomes

spermatozoa

result from spermiogenesis and is the final transformation stage

acrosome of spermatozoa

cap-like sac covering the head of the sperm

• contains digestive enzymes that help penetrate outer layer of ovum during fertilization

mitochondria of spermatozoa

multiply and coil tighly in the midpiece 

• produce large amounts of ATP for tail movement

flagellum of spermatozoa

enable motility of the sperm cell

• its microtubules are formed by centrioles

pseudostratified columnar epithelium with stereocilia

epididymis mucosal lining

sterocilia

nonmotile microvilli that function to … 

• complete spermiogenesis

• absorb excess fluid

• pass nutrients to developing sperm cells 

smooth muscle of epididymis

surrounds the epididymal tubules and propels sperm toward the tail

hypothalamus releases gonadotropin releasing hormone → anterior lobe of pituitary gland → follicle stimulating hormone and luteinizing hormone released → spermatogenesis activation

hormonal pathway of sperm cell production

follicle stimulating hormone

binds to sustentacular cells in walls of seminiferous tubules to stimulate them to produce androgen binding protein and inhibin

luteinizing hormone

binds to interstitial cells between seminiferous tubules to stimulate them to produce testosterone

• testosterone binds to androgen binding protein to form a complex that stimulates spermatogenic cells to mature into sperm cells

negative feedback control

maintains a steady, normal range of testosterone production in adult males

• rising testosterone levels: inhibit both the hypothalamus and pituitary gland

• inhibin: enhances negative feedback inhibition by also targeting the hypothalamus and pituitary gland