human embryology test 1

Embryology

the study of development from fertilization to birth

fertilization

the fusion of the sperm and egg

Developmental Events

fertilization, cleavage, blastulation, gastrulation, organogenesis

cleavage

early divisions of the embryo

blastulation

4 days after fertilization occurs; creation of a hollow cavity

gastrulation

migration of cells to form major tissue layer

organogenesis

development of organs

developmental stages

embryo (early embryo, embryonic organogenesis, fetus, newborn)

early embryo

1st three weeks; fertilization to gastrulation; cells created, but organs not yet forming

embryonic organogenesis

weeks 4-8; shape of structures change; organs form

fetus

9 weeks until birth; organs have mature shape; organs develop more functions

conception

starts at fertilization; is the beginning of life

pregnancy

condition of a woman carrying developing offspring in her body; this occurs from fertilization until birth

conceptus

the zygote/embryo/fetus which includes the embryo proper/fetus proper and the extraembryonic/extrafetal membranes

embryo proper/fetus proper

parts of embryo/fetus that contribute to structures that remain after birth

extraembryonic/extrafetal membranes

parts of the embryo/fetus that don't remain after birth such as the umbilical cord and the placenta

Methods of dating pregnancy

fertilization age, menstrual age, and gestational age

fertilization age

age of conceptus; starts at fertilization; generally used by embryologists

menstrual age

time since onset of last menstrual period; provides an easy way to date pregnancy; generally used by medical professionals such as nurses and doctors

Menstrual age = fertilization age + 2 weeks

gestational age

imprecise term indicating age of conceptus; used synonymously with both fertilization age and menstrual age

Trimesters

generally used by medical professionals; there are three roughly equal periods and each period is about three months; trimesters are clinical time periods, not developmental stages and are dated from menstrual age

Male primary sex organs

testes

male secondary sex organs

ducts including epididymis, vas deferens, ejaculatory duct, and urethra; glands including seminal vessels, prostate, and bulbourethral glands

testes

produce testosterone

testosterone

a masculinizing sex hormone that promotes sperm production, growth and maturation of reproductive system, and development of secondary sex characteristics

scrotum

sac of skin (thin layer) that encloses testes; it allows testes to hang outside of the body because sperm can't develop at body temperature

seminiferous tubules

area where sperm are formed and gain mature shape

rete testis

receive sperm from seminiferous tubules

epididymis

receives sperm from rete testis and sperm gain ability to swim here

vas deferens

receives sperm from the epididymis

ejaculatory duct

receives sperm from vas deferens and receives fluids from seminal vessel

urethra

receives sperm from ejaculatory duct, traverses length of penis, and takes sperm to outside

overall path of sperm

Seminiferous tubules => rete testis => epididymis => vas deferens => ejaculatory duct => urethra

semen

sperm + seminal fluid; it contains immunosuppressants which prevents the destruction of sperm by the immune system since the mother's immune system will attack foreign sperm cells

seminal fluid

fluid produced by male reproductive glands

seminal vesicles

produce most of seminal fluid; contains sugars to provide energy for the sperm; the fluid is alkaline which neutralizes acidic environment of the vagina; this acid can kill sperm and makes them move slower; also produces hormones which promote muscular contractions to move the sperm toward the egg

prostate

produces some of the seminal fluid; empties into the urethra and produces an antibiotic that boosts the immune system

bulbourethral glands

empty into the urethra and produces mucus; first fluid to enter urethra and cleans the urethra of any acidic urine to protect sperm; it also lubricates conjugal union

male external gentelia

penis

erection

an enlarged rigid state of the penis

erectile tissue

tissue around the urethra of the penis; this fills with blood to cause an erection

ejaculation

ejection of semen from penis and results in the loss of the erection

foreskin

flap of skin covering the end of the penis

circumcision

removal of the foreskin; pros include that it may reduce transmission risk of certain sexually transmitted diseases such as HIV and reduces risks of some pathologies such as penile cancer; cons include pain to a newborn, removes natural lubrication which may increase partner's dissatisfaction, surgical complications, and may not provide any lifetime benefit

female primary sex organ

ovaries

female secondary sex organs

ducts such as the uterine tubes, uterus, and vagina

ovaries

organs that produce oocytes

oocyte

an immature egg; also produce estrogens

estrogen

female sex hormone that regulates the fertility cycle, aids in pregnancy, and promotes the development of secondary sex characteristics

uterine tubes/fallopian tubes

tubes to the uterus

uterus/womb

where embryo/fetus is nourished and grows; located between bladder and rectum

endometrium

inner layer of uterus; receives and maintains the conceptus during pregnancy

myometrium

middle layer of uterus; muscular layer that pushes baby out

fundus

top of uterus that can be felt to estimate the size of the womb

body

middle of the uterus where implantation should occur

cervix

narrow area at lower area of uterus that produces cervical mucus that can block or allow passage through the cervix

vagina/birth canal

area of conjugal union; this is where the baby will exit; acidic environment the prevents bacterial growth and infection and kills sperm

external genitalia

vulva which includes clitoris, labia majora, labia minora, and vestibule

clitoris

sensitive erectile tissue

labia majora

larger tissue folds of vulva that surrounds labia minora

labia minora

smaller tissue folds of vulva (surrounds vestibule)

vestibule

space between labia minora that contains openings of vagina and the urinary system; produces mucus to provide lubrication during conjugal intercourse

anal intercourse damage

small anus size compared to vaginal opening or penis size; vagina can expand during conjugal union; anal intercourse can hinder control of defecation

disease transmission of anal intercourse

the anal tissue is more fragile which would provide pathogen access to sensitive tissues, the vaginal lubrication is absent and the tissue is thinner and less supported by muscle; blood vessels often rupture during penile-anal intercourse

gametogenesis

process of forming gametes

germ cells

cells used in reproduction

gamete

a mature germ cell; combine to form a new organism; a mature sperm and egg are gametes

somatic cell

a cell not used for reproduction

Why can't two somatic cells be used for reproduction?

somatic cell from dad has 2 sets of DNA and somatic cell from mom has 2 sets of DNA - 4 sets all together is bad; gametes need only 1 set of DNA - 1 set from dad + 1 set from mom = 2 sets which is normal

Sperm anatomy

head, midpiece, tail

sperm head

elongated "front" of sperm; contains acrosome which is a chemical filled area that helps sperm integrate with oocyte; nucleus holds DNA which is densely packed and wrapped around small proteins

Sperm tail

long, thin end of sperm that provides propulsion through fluid

sperm midpiece

middle part of sperm that contains mitochondria which is cell "organs" that produce energy and contains a little bit of DNA

spermatogenesis

gametogenesis of sperm that occurs in the seminiferous tubules

maturation steps of spermatogenesis

-Spermatogoni(um/a)

-Primary spermatocytes

-Secondary spermatocytes

-Spermatids

-Sperm

spermatogania

2 copies of DNA that can copy themselves and divide to provide cells needed to produce future sperm; before puberty they divide to grow in number and after puberty they divide to maintain number and produce sperm cells; division can occur throughout a male's lifetime but slows with age

primary spermatocyte

DNA of spermatogonium is duplicated and has 4 copies of DNA

secondary spermatocytes

primary spermatocyte divides and the DNA is divided between 2 secondary spermatocytes; each secondary spermatocyte now has 2 copies of DNA

spermatids

secondary spermatocyte divides and the DNA is divided between 2 spermatids so each spermatid contains 1 copy of DNA; these don't look like a sperm

sperm

morphologically mature male gametes

oogenesis

gametogenesis of the egg

maturation steps of oogenesis

-Oogoni(um/a)

-Primary oocyte

-Secondary oocyte + polar body I

-Ovum + polar body II

oogonia

contains 2 copies of DNA that can copy themselves and provides material for future ova; present in the embryo but none are present at birth because all have matured to primary oocytes

primary oocyte

DNA of oogonia is duplicated which makes 4 copies of DNA; these are present at birth and do not develop further until puberty

secondary oocyte + polar body 1

contains 2 copies of DNA and the primary oocyte divides unevenly; the larger cell is the secondary oocyte while the smaller cell is polar body 1 and the polar body will degenerate; secondary oocyte is expelled during ovulation

what is the purpose of the polar body?

allows oocyte to remove some excess genetic material and to keep most nutrients from cytoplasm

ovum + polar body 2

contains 1 copy of DNA and the secondary oocyte divides unevenly; the ovum is the larger cell while the polar body 2 is the smaller cell; polar body 2 removes excess genetic material and ovum is created in response to fusion of secondary oocyte with the sperm; the ovum is not fertilized, the secondary oocyte is what is fertilized; the sperm initiates production of polar body 2

ovulation

oocytes mature into a follicle; follicle wall ruptures and oocyte is expelled into body cavity

follicle

oocyte + surrounding cells

zona pellucida

a non-cellular membrane between the oocyte and follicle cells

follicle maturation

multiple follicles mature each cycle but only one follicle becomes dominant. the dominant follicle releases the oocyte; the ovulation of abnormal oocytes is prevented by the normal oocytes; follicles with non-ovulated oocytes degenerate and are absorbed

oocyte transport aids

Fimbria(e), corona radiata, cilia