Reproductive System Flashcards
1
Q
what does sexual reproduction require
A
- production of functionalized sex cells or gametes by adult organisms
- union of these cells (fertilization or conjugation) to form a zygote
- development of the zygote into another adult, completing the cycle
2
Q
what are gonads
A
- the gametes produced in specialized organs are called gonads
- the male gonads, called testes produce sperm in tightly coiled seminiferous tubules
- femal gonads called ovaries produce oocytes (eggs)
- some species are hermaphrodites and have both functional male and female gonads (ex: hydra and earthworm)
3
Q
What is Gametogenesis
A
- production of functionalized sex cells is called gametogenesis
- in males called spermatogenesis (sperm production) occurs iin seminiferous tubules of the testes
- in females called oogenesis (egg productino) occuring in the ovaries
4
Q
desribe fertilization
A
- union of the egg and sperm nuclei to form a zygote with a diploid number of chromosomes
- internal fertilization is practiced by terrestrial vertebrates providing a direct route for sperm to reach the egg cell: inc chance of fertilization -> female produce fewer eggs
- if early development of the offspring occurs outside mothers body more eggs will be laid to inc chance of offspring survival
- the amount of parental care after birth is also related to the number of eggs produced
*species that care for young produce fewer eggs
5
Q
describe the male reproductive system
A
- testes are located in an external pouch called scrotum that maintains the testes’ temp at 2-4 deg lower than body temp for sperm survival
- sperm pass from testes to vas deferens to ejaculatory duct and then to the urethra
- urethra passes through the penis and opens to the outside at its tip
- in males urethra is a common passageway for both reproductive and excretory systems
- testes are sites for testosterone production which reg secondary male sex characterisics (facial and pubic hair, voice changes)
6
Q
A
7
Q
explain spermatogensis
A
- occurs in seminiferous tubules
- diploid cells called spermatogonia differentiate into diploid cells called primary spermatocytes
- undergo 1st meiotic division forming 2 haploid secondary spermatocytes of equal size
- second meotic division produces 4 haploid spermatids which undergo a series of changes leading to mature sperm (spermatozoa)
- these are specialized for transporting the sperm nucleus tot he egg or ovum
8
Q
describe strucutre of a sperm cell
A
- elongated cell with a head, neck, body and tail
- head consists almost entirely of the nucleus, the tail (flagellum) propels the sperm while mitochondria in the neck and body provide energy for locomotion
- a caplike structure called acrosome derived from the Glogi apparatus develops over the anterior half of the head
- acrosoe contains enzymes needed to penetrate through the tough outer covering of the ovum
9
Q
descibe the female
A
- ovaries are found in the abdominal cavity below the digetive system, consists of thousands of follicles
- follicle = multilayered sac of cells that contains nourishes and protects an immature ovum
- follicle cell produces estrogen
~ 1/month immature ovum is released from the ovary into abdominal cavity and drawn by cilia into nearby ovictduct (fallopian tubes)
- each fallopian tube opens into the upper end of the uterus -> the site of fetal development
- lower narrow part of uterus is called the cervix which connects wth the vaginal canal: site of sperm deposition and passageway through which abby is expelled during birth
10
Q
describe oogenesis
A
- production of female gametes occuring in ovarian follicles
- at birth most of immature ova (primary oocytes) that female will produce are already in ovaries
- primary oocytes are diploid cells that form by mitosis in ovary
- after menarche (1st tiem female menstrates) one primary oocyte completes meiosis 1 yeilding 2 daughter cells of unequal size (secondary oocyte and polar body)
- secondary oocyte is expelled from the follicle during ovulation
* meiosis II does not occur until fertilization
- the oocyte cell membrane is surrounded by two layers inner is zona pellucida and outer is corona rediata
11
Q
what triggers meiosis II
A
- two surrounding layers of oocyte membrane zona pellucida and corona radiata are penetrated by a sperm cell yeilding two haploid cells: mature ovum and another polar body
- first generated polar body from meiosis I can also undergo meiosis II, but polar bodies will degenerate
- mature ovum is a large cell containing cytoplasm, RNA, organelles, and nutrients needed by the developing embryo
- when polar bodies are formed they lack these resources having given them to the developing oocyte
12
Q
what are the female sex hormones and what are they regualted y
A
- ovaries synthesize and secrete female sex hormones: estrogens and progeterone
- secretion is regulated by luteinizing hormone and follicle stimulating hormone whivh are regulated by gonadotropin releasing hormone (GnRH)
13
Q
what are estrogens
A
- steroid hormones necessary for normal female maturation
- they stimulate the development of the female reproductive tract and contribute to the developmeny of seondary sexual characterisics and sex drive
- estrogens are responsible for the thickening of the endometrium
- estrogens are secreted by the ovarian follicles and the corpus luteum
14
Q
what is progesterone
A
- steroid hormone secreted by the corpus luteum durign the luteal phase of menstrual cycle
- progesterone stimulates the development and maintenance of the endometrial walls in preparation for implantation
15
Q
what plays important roles in the menstrual cycle and its phases
A
hormonal secretions of the ovaries, hypothalamus and anterior pituitary play important roles in menstrual cycle
- divided into follicular phase, ovulation, luteal phase and menstruation
16
Q
describe the follicular phase
A
- begins with the cessation of the menstrual flow from the previous cycle
- during this phase FSH from the anterior pituitary promotes the development of the follicle which grows and begins to secrete estrogen
17
Q
describe ovulation
A
- midway through the cycle ovulation occurs
- mature follicle bursts and releases an ovum
- ovulation is caused by a surge in LH thta is preceded and in part caused by a peak estrogen level
18
Q
describe the luteal phase
A
- after ovulation, LH induces the ruptured follicle to develop into the corpus luteum
- corpus luteum secretes estrogen and progesterone
- progesterone causes the glands of the endometrium to mature and produce secretions that prepare it for the implantation of an embryo
- progesterone and estrogen are essential for the maintenance of the endometrium
19
Q
describe menstruation
A
- if the ovum is not fertilized the corpus luteum atrophies
- causes a drop in progesterone and estrogen levels causing the endometrium to slough off causing menstrual flow
- if fertilization occurs the developing placenta produces hCG (human chorionic gonadotropin) maintaining the corpus luteum and thus the supply of estrogen and progesterone that maintains the uterus
- eventually the placents takes voer production of these hormones and hCG is no longer produced
20
Q
how does fertilization occur
A
- egg can be fertilizaed 12-24 hours after ovulation
- occurs in the lateral, widest portion of the fallopian tube
- sperm must travel throguh the vaginal canal, cervix, uterus and into the fallopian tubes to reach the ovum
- sperm remains viable and capable of fertilization 1-2 days after intercourse
21
Q
what is the first barrier to sperm how does it overcome
A
- corona radiata
- enzymes secreted by the sperm aid in penetration of the corona radiata
- the acrosome is responsible for penetrating the zona pellucida: it releases enzymes that digest this layer thereby allowing the pserm to come into direct contact with the ovm cell membrane
- sperm then forms a tubelike structure called asrosomal process which extends to the cell membrane and penetrates it
- fuses the sperm cell membrane with that of the ovum
- sperm nucleus enters ovums cytoplasm
- fertilization causes ovum to compelte meiosis II
22
Q
describe the cortical reaction in the ovum
A
- triggered by acrosomal reaction
- causes calcium ions to be released into the cytoplasm
- this initiates a series of reactions that result in the formation of the fertilization membrane
- this is a hard layer that surrounds the ovum cell membrane and prevents multiple fertilizations
- release of Ca2+ also stimualtes metabolic changes within the ovum greatly inc metabolic rate
- this is followed by fusion of the pserm nucleus with the ovum nucelus forming a diploid zygote
- frist mitotic division of zygote soon follows
23
Q
explain how monozygotic twins are formed
A
- result when a single zygote splits into two embryos
- if the splitting occurs at th two-cell stage of development, the embryos will have separate chorions an separate placentas
- if occurs as blastula stage embryos will only have one chorionic sac and will share the same placenta and possible an amion
- occasionally when division is incomplete results in conjoined twins (will liekly share some organs)
- monozygotic twins are genetically identical bc they develop from the same zygote
*wll be same sex and blood type
24
Q
explain dizygotic twins
A
- result when two ova are released in one ovarian cycle and are fertilized by two different sperm
- the two emryos implant in the uterine wall individually and each develops its own placenta, amnion and chorion
- faternal twins share no more charcteristics than siblings bc they develop from two distinct zygotes
25
Q
what is embryology
A
- study of the development of a unicellular organism into a complete multicellular organism
- over nine months a unicellular human zygote undergoes cell division, cellular differentiation and morphogensis in preparation for life outside uterous
26
Q
explain fertilization in terms of early developmental stages
A
- egg can be fertilized 12-24 hours after ovulation
- fertilziation occurs in the widest portion of the oviduct where the sperm traveling from the vagina encounter an egg
- if more than one egg is fertilized faternal (dizygotic) twins may be convieved
- idential (monozygotic) twins occur when zygote divides into two separate embroyes
27
Q
what deos cleavage refer to
A
- early embryonic development is characterized by a series of rapid mitotic divisions called cleavage
- lead to an inc in cell number w/o corresponding growth in cell protoplasm (total volume of cytoplasm remains constant)
- cleavage results in progressively smaller cells with an inc ratio of nuceli to cytoplasm
- also inc surface-to-volume ratio of each cell thereby improving gas and nnutrient exchange
28
Q
when do the initial cleavages occur?
A
- first complete cleavage ocurs approx 32 hours after fertilization, 2nd after 60 hours and 3rd aftre 72 hours
- at this point 8 celled embryo reaches the uternus
- as cell division continues a solid ball of embryonic cells known as the morula is formed
29
Q
describe blastulation
A
- begins when the morula develops a fluid-filled cavity called the blastocoel
- by the fourth day becomes a hollow sphere of cells called the blastula
- blastula is the stage of embryo that implants in the uterus
- emergency contraception works partially by inhibiting inplantation of the blastula in the uterus (why its most effective if taken within 72 hours of time of potential fertilization)
30
Q
what is an ectopic pregnancy
A
- embryo implants outside the uterus (ex in fallopian tube)
- embryo cannot be maintained for long outside the uterus, it will abort spontaneously and hemorraging will follow
- ectopic pregnancies can be fatal is not caught in time and managed properly
31
Q
what is gastrulation
A
- after second week the embryo is fully implanted in the uterus and cell migrations transform the sincle cell layer of blastula into three layered structure called gastrula
- these 3 primary germ layers are responsible for differential development of the tissues, organs and systems of the body at later stages of growth
layers: ectroderm, endoderm and mesoderm
32
Q
describe the ectoderm
A
- gives rise to the integument (including epidermis, hair, nails and epithelium of the nose, mouth and anal canal)
- also lens of eye, retina and the nervous system
33
Q
describe the endoderm
A
- gives rise to epithelial linings of the digestive and respiratory tracts (including the lungs) and parts of the liver, pancreas, thyorid and the bladder lining
34
Q
describe the mesoderm
A
- gives rise to the musculoskeletal system, circulatroy system, excretory system, gonads, connective itssue throughout the body and portions of digestive and respiratory organs
35
Q
what is neurulation
A
- by the end of gastrulation, regions of the germ layers begin to develop into rudimentary nervous system
- the process is known as neurulation and starts before 3rd week
- a rod of mesodermal cells (notochord) develops along the longitudinal axis of the embryo under the doral layer of ectoderm
- has an inductive effect on overlying ectoderm causing it to bend inwards and form a groove along the dorsal surface
- fold on either side of groove, folds grow upwards and will fuse to forma closed tube (this is the neural tube, gives rise to the brain and spinal chord)
- once the neural tube formed it detaches from surface of ectoderm
36
Q
what are cells at the tip of neural fodl called and what will they give rise to
A
- called neural crest cells
- migrate laterally and give rise to many components of the peripheral nervous system including: sesory ganglia, autonomic ganglia, adrenal medulla and schann cells
37
Q
what happens if the neural tube does not close properly
A
- spinal bifida
- opening can be corrected surgically but most patients will have neurological impairments
- incidence can be decreased if mother takes folic acid aupplements during pregnancy
38
Q
what are the final stages of the developmental process
A
Organogenesis: the body organs begin to form. in this process cells interact, differentiate and change physical shape, proliferate and migrate
Growth: Organs inc in size, which is a continual process from infancy to childhood to adulthood
Gametogenesis: eggs develop in women and sperm in men, permitting reproduction to occur
39
Q
how does fetus get oxygen
A
- growing fetus recieves oxygen directly from its mother through specialized circulatory system
- system not only supplies oxygen and nutrients but removes carbon dioxide and metabolic wastes
- two components of this sytem are placenta and umbilical cord which both develop in the first few weeks after fertilization
40
Q
what is the placenta and umbilical chord
A
- outgrowths of the four extra embryonic membranes formed during development: amnion, chorion, allantois and yolk sac
Amnion:
- thin tough membrane containing a watery fluid called amnionic fluid
- acts as a shock absorber of external pressure during gestation and localized pressure from uterine contractions during labour
Chiron
- where placenta formation begins
- membrane that completely surrounds the amnion
- assists in transfer of nutrients from mother to fetus
Allantois
- this membrane, develops as an outpocketing of the gut
- blood vessels of allantoic wall enlarge and become umbilical vessels which will connect the fetus to developing placenta
Yolk sac
- site of early developmen of blood vesels, becomes associated with imbilical vessels
41
Q
A
42
Q
what is gestation
A
- human pregnancy
- 9 months, 266 days
- can be divided itno 3 trimesters
43
Q
describe the first trimester
A
- major organs begin to develop
- heart begins to heat at 22 days and soon after eyes, gonads, limbs, and liver start to form
- by five weeks the emrbyo is 10 mm in length, by 6 weeks its 15mm
- cartilaginous skeleton begins to turn into bone by week 7
- at end of 8 weeks most organs have formed, brain is fairly developed and embryo is reffered to as fetus
- at end of 3rd month its 9cm long
44
Q
descibe the second trimester
A
- fetus grows a lot and begins to move in amniotic fluid
- face appreas human and toes and finger elongate
- by end of 6th month its 30-36 cm long
45
Q
describe the third trimester
A
- seventh of eighth month are charcaterized by continued growth and further brain development
- during ninth month antibodies are transported by highly selective active transport from mother to fetus for protection against foreign matter
- growth rate slows and fetus becomes less active bc it has less room to move
46
Q
describe child birth and maturation
A
- accomplished by labour, series of uterine contraction
- can be divided into 3 stages- 1st stage; cervix thins and dilates and amniotic sac ruptures releasing its fluids (contractions mild)
- 2nd stage characterized by rapid contractions resulting in birth of the baby
- final stage, uterus contracts and placenta is expelled and umbilical chord
