Growth and Development

spermatozoa

male gamete

spermatogenesis

process by which the spermatogonia can become a mature sperm, spermatozoa

beings around puberty

spermatocyte —> meiosis 1 —> 2 secondary spermatocyte —> meiosis 2 —> spermatids (differentiate to form heads and tails) —> spermatozoa

ova

female gamete

oogenesis

primitive female sex cells, or oogonia, become mature ova

begins fetal period

cytoplasm not equally divided among daughter cells

oogonia —> mitosis —> primary oocytes —> develops (P1) of meiosis before birth —> primary follicle —> ~20 start meiosis —> thetca cells —> produce androgen (estrogen) —> secondary follicles —> go to ovary’s surface —> graafian follicle —> meiosis continues and produces secondary oocyte and first polar body (stops at M2) —> ovulation —> fertilization —> meiosis 2 —> zygote

meiosis

orderly arrangement and distribution of chromosomes that reduces the number of chromosomes in each daughter cell to half the number present in the parent cell

diploid

46 chromosomes (23 pairs)

haploid

23 chromosomes (per sex cell)

interphase

DNA molecules replicates and become chromatids (attached at centromere)

chromosome

condensed chromatid

prophase 1

homologous pairs of chromosomes are moved to together to form groupings called tetrads

anaphase 1

tetrads split (chromosomes, not chromatids)

crossing over

chromatid segment of each chromosome crosses over and becomes part of the adjacent chromosome (reshuffles genes)m

metaphase 1

chromosomes align along the equator of the spindle fibers

primary follicle

granulosa cells develop around each primary oocyte

theca cells

what some of the granulosa cells differentiate to become

androgen

steroids produced by theca cells

become estrogen

secondary follicles

when surrounding primary follicles begin to mature and theca cells differentiate and produce estrogen

migrate towards surface of ovary

antrum

fluid filled space in each mature follicle (on surface of ovary)

graafian follicle

mature vesicular ovarian follicle ready to burst open from ovary’s surface

ovulation

release of an oocyte from a burst follicle (graafian) into the abdominopelvic cavity —> fallopian tubes

under the luteinizing hormone (LH)z

zygote

fertilized ovum

what primary oocyte produces

3 polar bodies and 1 mature ovum

mucous strands in cervical canal

guide sperm on way to uterus

thermotaxis

sperm are attracted to warmer temperatures of the uterine tube

zona pellucida

jellylike film in layers around the ovum

orona radiata

outer envelope of cumuluus cells in ovum’s surrounding layers

acrosome reaction

release of enzymes from acrosome that breaks down outer layers of ovum

cumulus cells release progesterone and molecules tat increase sperm mobility

fertilization membrane

thick zona pellucida that stops other sperm from entering egg

prenatal period

conception (fertilization) to birth

embryology

science of development of offspring before birth

morula

solid mass of dividing zygote

form an inner cavity as it continues to divideb

blastocyst

hollow ball of cells that reached the uterus

implantation

after 1 week of fertilization

blastocyst is implanted in uterus lining (start of pregnancy)

trophoblast

outer wall of blastocyst

yolk sac and amniotic cavity

inner cell of blastocyst mass forms a structure with 2 cavities

yolk sac

site of hematopoiesis

produces stem cells that migrate to two embryonic gonads that develop into oogonia and spermatogonia

amniotic cavity

fluid filled, shock absorbing sac

bag of waters where embryo floats

chorion

develops from the trophoblast to become a fetal membrane in the placenta

placenta

anchors offspring in uterus and provides a bridge for nutrients and waste products between mom and baby

chorionic villi

extensions of blood vessels of chorion that brings embryonic circulation to placenta

placental tissue

separates the maternal and fetal blood supplies

protects baby from harmful substances

secretes human chorionic gonadotropin (hCG)

human chorionic gonadotropin (hCG)

stimulate the corpus luteum to continue secretion of estrogen and progesterone

decreases once placenta starts secreting estrogen and progesterone

gestation

length of pregnancy

divided into 3 month segments (trimesters)

first trimester

first day of last period to end of 12th week

second trimester

12th-28th week

third trimester

28th-delivery

stem cells

unspecialized cells that reproduce to form specific lines of specialized cells

potency (stemness)

capable of producing many different kinds of cells in the body

topipotent

can produce any type of cell

found in zygote

pluripotent

embryonic stem cell that can produce a broad range of cell types; found in embryonic germ layers

multipotent

produce a few cell types and thus maintain functional populations of specialized cells

primary germ layers

develop in 1st trimester

cells of the embryonic disk differentiate into distinct type that form 3 layers

endoderm

inner germ layer

forms linings of tracts and glands

ex. respiratory tract, GI tract, tonsils, pancreatic ducts, hepatic ducts, and urinary tract, thymus, thyoid, parathyroid

ectoderm

outer germ layer

forms around periphery of the body

ex. epidermis of skin, enamel of teeth, cornea and lens of eye, brain and spinal cord

mesoderm

middle germ layer

most of organs

ex. dermis of skin, skeletal muscles and bones, glands, kidneys, gonads, and circulatory system

histogenesis

process where primary germ layers develop into tissues

organogenesis

tissues arranging into organs

partuition

birth

uterus contracts and causes cervix to dilate (amniotic sac ruptures)

birthing process

high levels of cortisol —> drop in hGC —> drop in progesterone levels —> oxytocin (brake on muscle) is released —> labor contractions

1st stage of labor

onset of uterine contractions until dilation of cervix is complete

6-24 hrs

2nd stage of labor

maximal cervical dilation to baby’s exit of vagina

few minutes-1 hr

3rd stage of labor

expulsion of placenta through vagina

~15 minutes after baby’s birth

cesarean section (c-section)

newborn is delivered through an incision in abdomen and uterine wall

identical twins

splitting of embryonic tissue from the SAME zygote

fraternal twins

fertilization of 2 different ova by 2 different sperm

postnatal period

begins at birth and until death

infancy

birth - 18 months

early - has one spinal curvature

neonatal period

first 4 weeks of infancy

APGAR score

test used to assess general condition of a newborn (5 criteria)

childhood

end of infancy to puberty

early childhood

growth continues at a rapid pace but month-to-month gains are less consistent

puberty

12-14 Girls

14-16 Boys

sexually mature

gerontology

study of aging

senescence

degenerative aging in older adulthood

a gradual decline occurs in every major organ system in the body

progeria

where a person appears to age rapidly

skeletal system

bone density decrease —> change texture, calcification, and shape

lipping - limit range of motion

decreased bone size —> inc. risk of fracture

avoided with exercise and calcium intake

muscular system

mass decreases to about 90% by 50 and 50% by 80

fibers decrease but can be offset through exercise

slow function of muscle organs

integumentary system

skin becomes dry, thin, and inelastic

pigmentation changes and thinning hair

urinary system

number of nephron units in kidney decrease by ~50% between 30 and 75

decreased blood flow in kidneys —> reduces excretory capacity, inability to empty completely

respiratory system

costal cartilages become calcified

decreased strength of respiratory muscles

respiratory efficiency decreases

cardiovascular system

degenerative heart and blood vessel disease

atherosclerosis (buildup of fatty deposits)

arteriosclerosis (loss of elasticity)

hypertension (high blood pressure)

reproductive systems

mechanism of sexual response may change

decrease in fertility

menopause between 45-55 for females

sense organs

decline in performance and capacity

presbyopia

farsightedness

cataract

cloudy lens

glaucoma

increased pressure in eyeball

benefits in aging

improved brain functions:

less anxious and fearful

less resistant to happiness

better interpretation of visual information

improved problem solving and wisdom

developed countries cause of death

heart disease, cancer, stroke, cerebrovascular accident

developing countries causes of death

heart disease, stroke, infectious diseases, HIV/AIDS, diarrheal disorders, malaria