Bio K103 Chapter 50 and 51: Reproduction and Fertilization

single parent so no extra effort required to find a mate, number increases rapidly in favorable environment

what are the advantages of asexual reproduction?

genetically identical to parent (no variability), difficult to evolve

what are the disadvantages of asexual reproduction?

fission, budding, fragmentation, parthenogenesis

what are the types of asexual reproduction?

division along entire longitudinal or transverse plane

what is fission?

protists

what is an example of an organism that reproduces via fission?

when viable offspring bud off from an adult

what is budding?

sponges and cnidarians

what are examples of organisms that reproduce via budding?

when the body of animal breaks into several pieces, each piece regenerates missing parts to develop whole animal

what is fragmentation?

some flatworms and annelids

give examples of animals that reproduce via fragmentation

place that if cut during fragmentation, will not grow/regenerate into a whole animal

what is the longitudinal genetic axis?

when an unfertilized egg develops into an adult without a partner to fertilize it, typically haploid

what is parthenogenesis?

sexual reproduction

most species that perform parthenogenesis alternate with ___

insects, crustaceans, nematodes, gastropods, fishes, amphibians, reptiles

give examples of organisms that reproduce via parthenogenesis

promotes genetic variety, favorable for evolution in changing environments

what are the advantages of sexual reproduction?

less efficient (mate required), requires more energy than asexual

what are the disadvantages of sexual reproduction?

production and fusion of two haploid gametes

what is the requirement for sexual reproduction?

the motile object

in sexual reproduction, what is considered the sperm?

the nonmotile object

in sexual reproduction, what is considered the ovum (egg)?

external fertilization and internal fertilization

what are the methods of sexual reproduction?

simultaneous release of sperm and egg into water, mixing/fertilization occurs outside body

what is external fertilization?

sperm is deposited into or enters the female's reproductive tract

what is internal fertilization?

when a single individual produces both eggs and sperm (monoecious), type of sexual reproduction

what is hermaphroditism?

some species (like tapeworms) can self-fertilize, often prevented by development of sperm and eggs at different times

describe self-fertilization in hermaphroditism

they are the same

how do the structures of males and females compare as embryos?

presence or absence of masculinizing factors during critical period of embryonic development

what determinates sex?

determined at fertilization, chromosomes: XX and XY

what is genotypic sex?

controlled by SRY gene on short arm of Y, testes determining factors (TDF) activates other genes that lead to development of male gonads

what is phenotypic sex?

they secrete hormones that drive development of male internal and external structures

what happens once testes differentiate?

on chromosome 19

where is the gene for anti-mullerian hormone (AMH) located?

stimulates degeneration of mullerian ducts (prevents development of female structures)

what does AMH do?

sertoli cells and interstitial cells of leydig (endocrinocytes)

what are the cells associated with the testes?

secrete AMH, androgen binding protein (ABP), and inhibin

what do sertoli cells do?

secrete testosterone and dihydrotestosterone

what do interstitial cells of leydig do?

a more potent form of testosterone

what is dihydrotestosterone?

stimulate differentiation of wolffian ducts into non-testes structures in males

what does secretion of testosterone and dihydrotestosterone do?

vas deferens, seminal vesicles, prostate gland

what are examples of structures that wolffian ducts differentiate into in males?

drives movement of testes into scrotum

what does testosterone do in later fetal development?

secrete fluids into ejaculatory ducts and urethra

what is the purpose of accessory structures in the male reproductive system?

prostate gland, seminal glands (vesicles), bulbo-urethral gland

what are the accessory organs of the male reproductive system?

carries sperm in semen secreted by accessory organs (nourishment and support), involved in expelling sperm from reproductive tract

what are the functions of the duct system in the male reproductive system?

vas deferens, blood and lymphatic vessels, nerves

what structures make up the spermatic cord?

protrusion of abdominal visceral tissues into inguinal canal

what is an inguinal hernia?

houses spermatic cord, provides path for the testes to descend into the scrotum during fetal development

what is the inguinal canal in males?

ovoid structures located outside abdominopelvic cavity

what are testes?

lobules

testis is divided into ___

sac-like structure that protects and supports the testes

what is the scrotum?

cooler than internal body temp

what temperature is required for sperm production?

dartos muscle- smooth, wrinkles skin to reduce heat loss

cremaster muscle- skeletal, raises/lowers testes is response to temperature or arousal

what muscles regulate temperature for sperm production and how?

tightly coiled seminiferous tubules

what does each lobule of the testes contain?

beginning of tubular network, tightly coiled branches in lobules, actual site of sperm production in wall of tubule

what are seminiferous tubules?

spermatogenic cells and sustentacular cells (sertoli/nurse cells)

what cell types do seminiferous tubules contain?

sperm-forming cells, 2n, one stays behind and the other undergoes meiosis

what are spermatogenic cells?

support sperm production with nutrients

what do sertoli cells do?

located between seminiferous tubules, produce and secrete androgens (mainly testosterone)

what are interstitial (leydig) cells?

muscle-like cells surrounding seminiferous tubules, contract to push sperm and testicular fluid through tubules

what are myoid cells?

network of tubules in posterior testis, receives sperm from seminiferous tubules, transports sperm to efferent ductules onto epididymis

what is the rete testis?

site of sperm maturation and storage, absorbs excess testicular fluid, provides nutrients to sperm, completes maturation process of sperm

what is the epididymis (ductus epididymis)?

stored for months until it is ejaculated or reabsorbed

what happens to sperm if it is unused?

begins at tail of epididymis and continues to seminal vesicles, can store sperm for months, secretes factors to prevent sperm capacitation

what is the ductus deferens?

rete testis, epididymis, ductus deferens, muscular layer, ejaculatory duct, urethra

what are the parts of the male duct system?

three layers of smooth muscle, contracts during ejaculation to move sperm forward along tract

what is the muscular layer of the male duct system?

section between vas deferens and urethra, shortest segment, passes through prostate, receives secretion from seminal vesicle

what is the ejaculatory duct?

runs from bladder through prostate and penis, has dual function- part of urinary and reproductive system

what is the urethra in males?

exocrine glands that produce lipid portion of semen

what are accessory sex glands?

paired glands near urinary bladder, contribute to most of semen volume

what are seminal vesicles?

semen

where does nourishment for sperm come from?

fructose, prostaglandins, coagulating proteins

what are the components of seminal secretions?

fuel for ATP synthesis in sperm

what is the function of fructose in seminal secretions?

stimulate smooth muscle contraction in reproductive tract (male and female), increases sperm viability, may also thin mucus for easier passage of sperm

what is the function of prostaglandins?

mix with enzymes from prostate, form temporary clot of semen in female reproductive tract

what is the function of coagulating proteins?

female

is the mucus in male or female reproductive tract thicker?

alkaline, to neutralize acids in male urethra and female reproductive tract

what is the pH of seminal secretions?

seminal vesicles, prostate gland, bulbourethral (cowper's) glands,

what are the accessory sex glands in the male reproductive system?

inferior to urinary bladder, surround urethra and ejaculatory ducts

where is the prostate gland located?

20%-30%

how much semen does the prostate gland account for?

complex of 20-30 tubular glands disperse among smooth muscle and connective tissue

describe the structure of the prostate gland

smooth muscle contractions squeeze prostatic secretions into prostatic urethra

what happens in the prostate gland during ejaculation?

citrate, prostate specific antigen (PSA)/other enzymes, antimicrobial chemicals

what are the components of prostatic secretions?

sugar found in prostatic secretions that sperm can utilize for ATP synthesis

what is citrate?

dissolve semen clot in female reproductive tract, allows sperm to proceed further into tract

what do PSA and other enzymes do in prostatic secretions?

inhibit some bacterial growth, decreases infection risk in female reproductive tract

what do antimicrobial chemicals in prostatic secretions do?

alkaline, neutralizes acids in urethra and female reproductive tract

describe the pH of prostatic secretions

marble-sized, paired glands at base of penis, connects to urethra

what are bulbourethral (cowper's) glands?

thick, alkaline mucus-like fluid, helps neutralize urethra from any remaining acidic urine

what do bulbourethral (cowper's) glands secret and what does it do?