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
what is embryology
- 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
explain fertilization in terms of early developmental stages
- 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
what deos cleavage refer to
- 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
when do the initial cleavages occur?
- 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
describe blastulation
- 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
what is an ectopic pregnancy
- 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
what is gastrulation
- 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
describe the ectoderm
- 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
describe the endoderm
- 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
describe the mesoderm
- gives rise to the musculoskeletal system, circulatroy system, excretory system, gonads, connective itssue throughout the body and portions of digestive and respiratory organs
35
what is neurulation
- 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
what are cells at the tip of neural fodl called and what will they give rise to
- 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
what happens if the neural tube does not close properly
- 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
what are the final stages of the developmental process
**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
how does fetus get oxygen
- 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
what is the placenta and umbilical chord
- 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
42
what is gestation
- human pregnancy
- 9 months, 266 days
- can be divided itno 3 trimesters
43
describe the first trimester
- 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
descibe the second trimester
- 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
describe the third trimester
- 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
describe child birth and maturation
- 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
