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Reproductive & Development (Meiosis (Telophase 1 (2 new haploid cells…
Reproductive & Development
Meiosis
Telophase 1
2 new haploid cells form
Prophase 2
Each cell starts mitosis; Nuclear membrane breaks down; Becomes chromosomes
Anaphase 1
Separates pairs of chromosomes
Metaphase 2
Chromosomes line up in a plane
Metaphase 1
Chromosomes line up (create a plane); during prophase and metaphase crossing over occurs
Anaphase 2
Chromosomes are separated
Prophase 1
Nuclear membrane goes away; Chromosomes pair up (tetrad)
Telophase 2
4 unique haploid cells form
Meiosis makes gametes for reproduction
Female Reproductive System
Parts of reproductive
Vagina
thick walled, fibromuscular tube; connects the uterus to the outside of the body and functions as the birth canal; it also receives the penis during intercourse and serves as a passageway during menstruation
Uterus
pear shaped, thick walled muscular organ within the pelvic cavity;
Functions: the uterine lining serves as a place for a fertilized oocyte to implant; Supports, protects, and nourishes the developing embryo/fetus; then ejects the fetus at birth
Uterus is separated into the following regions
Body: middle region, major part of uterus and is composed of a thick wall of smooth muscle
Isthmus: narrow, constricted inferior region of the body that is superior to the cervix
Fundus: broad, curved superior region extending between the lateral attachments (fallopian tubes)
Cervix: narrow inferiormost portion of the uterus; connects to the vagina; has mucin-secreting glands that help form the mucus plug
Ovary
two oval organs located within the pelvic cavity, lateral to uterus
Broad ligament: mesovarium secures each ovary to a broad ligament, which is a drape of peritoneum that hangs over the uterus
Ovarian ligament: each ovary is anchored to the posterior aspect of the broad ligament by an ovarian ligament, which is the superior portion of the round ligament of the uterus
Suspensory ligament: attaches to the lateral edge of each ovary and projects superolaterally to the pelvic wall
Mesovarium: a double fold of peritoneum; attaches to each ovary at its hilum
Fallopian tube
tubes that extend laterally from the uterus toward the ovaries
Ampulla: expanded region medial to the infudibulum; fertilization of an oocyte typically occurs here
Isthmus: extends medially from the ampulla toward the lateral wall of the uterus
Infundibulum: free funnel-shaped lateral margin of the tube; has numerous fingerlike folds called fimbriae
Parts of menstrual cycle
Primordial follicle
Females are born with these; inactive until puberty
Primary follicle
Once puberty starts the primordial follicles each month will start to transform into primary follicles; 1 will complete the process the others will stop
Secondary follicle
forms from a Primary follicle; has many layers of granulosa cells and a fluid filled space called antrum. In the antrum is serous fluid that continues to build up and the oocyte moves to one side of the follicle
Vesicular follicle (mature oocyte)
is also called a graafian follicle; it forms from a secondary follicle; this follicle becomes large and has a secondary oocyte surrounded by a zona pellucida and the corona radiata, numerous layers of granulosa cells and a large fluid filled, cresent shaped antrum
Corpus luteum
the oocyte will expel from the follicle when it ruptures this is known as ovulation; remnants of the follicle will turn into a yellowish structure; this secretes progesterone and estrogen, these hormones prefer the uterus for implantation
Corpus albicans
the corpus luteum undergoes regression it turns white and becomes connective tissue scar; most are completely reabsorbed, only a few will remain in the ovary
Menstrual cycle
Follicular phase
Occurs approximately during days 1-13 of the 28 day cycle
The beginning of the follicular phase, FSH and LH stimulate about 20 primordial follicles to mature into primary follicles. As follicles develop they secrete inhibin to stop more follicles from maturing.
Once a primary follicle matures it becomes a secondary follicle. LH causes the volume of fluid in the antrum to increase, the oocyte is pushed to one side of the follicle, and it is surrounded by cells
As the secondary follicle matures into a vesicular follicle the oocyte has finished meiosis 1 and two cells form. One cell will become a polar body while the other will continue to mature and become a secondary oocyte.
Ovulation
Occurs on day 14 of the 28 day cycle
It is defined as the releasing of the secondary oocyte from the follicle.
Typically occurs each month; ovaries take turns releasing oocytes
Occurs only when there is a peak in LH secretion
Luteal Phase
Occurs during day 15-28 of the 28 day cycle
The remaining follicle particles become the corpus luteum
The corpus luteum serves as a temporary endocrine gland, secreting progesterone and estrogen; this prepares the uterus lining to thicken preparing for the implantation of a fertilized oocyte. The corpus luteum has a life span of about 10-13 days if the oocyte is not fertilized.
After this time the corpus luteum regresses and becomes the corpus albicans. As the coprus luteum regresses the levels of progesterone and estrogen drop causing the shedding of the uterus lining which is a females period.
Male Reproductive System
Epididymis
comma shaped structure composed of internal duct and an external covering of connective tissue; storage of sperm until they are fully matured and capable of motility
Vas deferens
tube in which sperm exit the testis and is taken to the prostate gland.
Prostate gland
includes submucosal glands that produce mucin; contribute to the seminal fluid.
Seminal fluid:milky fluid that is weakly acidic and rich in citric acid, seminalplasmin, and prostate-specific antigen (PSA).
Testis
Septa: delicate connective tissue
Lobules: the septa is subdivided into about 250 separate lobules
Seminiferous tubules: each lobule contains up to 4 extremely convoluted, thin, elongated seminiferous tubules
Sustentacular cells: non-dividing support cells; provide a protective environment; nourish the developing sperm; also if sperm count is high will secrete inhibin to stop/slow down sperm production
A population of dividing germ cells that continuously produce sperm beginning at puberty
Ejaculatory duct
Once the vas deferens enters the prostate gland it becomes the ejaculatory duct; conducts sperm and seminal fluid toward the urethra
Penis
houses the urethra; the body is called the penis, the tip is called the glans
Urethra
transports semen from both ejaculatory ducts to the outside of the body
Spermatogenesis
All sperm develop from primordial germ cells called spermatogonia; These are diploid cells that lie near the base of the seminiferous tubule, surrounded by a sustentacular cell
To produce sperm, spermatogonia divide by mitosis and produce a new spermatogonium,
Primary spermatocytes are diploid and undergo meiosis; the two cells produced are called secondary spermatocytes.
Secondary spermatocytes are haploid cells; they are still surrounded by the sustentacular cells but are now closer to the lumen of the seminiferous tubule
Secondary spermatocytes complete meiosis 2 to form spermatids; spermatids are still in the sustentacular cell, but are very near to the lumen of the seminiferous tubule; spermatids still have a circular appearance
The final stage is called spermiogenesis, the newly-formed spermatids differentiate to become mature spermatozoa or sperm; during this process the spermatids shed the excess cytoplasm and its nucleus elongates
Midpiece: neck region containing mitochondria and a centriole; mitochondria provides energy to move the tail
Tail: flagellum, forms from the organized microtubules within the cell; provides motility
Acrosome cap: forms over the nucleus; contains digestive enzymes that help penetrate the secondary oocyte for fertilization
Development
Embryonic
Week Three
Neural tube
Somites forming
Primitive streak
Heart forming
Heart beating
Amnion nearly covers embryo
Chorion well developed
Week Four
Somites present
Embryo fully covered by amnion
Internal organs forming
Cartilage skeleton and muscles develop
Spinal cord and brain forming
Facial features and ears develop
Week Two
Chorionic villi appear
Inner cell mass undergoes gastrulation to form the embryonic disk of germ layers
Endoderm
inferior layer; develops into the digestive system and its derivatives
Mesoderm
middle layer; develops into the circulatory system, excretory system, most of the reproductive system, skeletal system, and muscles
Ectoderm
superior layer; develops into the nervous system, sense organs, skin
Amnion forms
Month Two
All internal organs are complete, some functioning
Extremities develop from limb buds
Cartilage skeleton and muscles complete
Placenta and umbilical cord function
Facial features and ears are nearly complete
Embryo assumes a human apperance
At the end of week 8 embryo becomes a fetus
Week One
Morula-solid ball of cells
Bastocyst- hollow ball of cells with inner cell mass
Cleavage of zygote
Implantation in endometrium of the uterus
Fertilization occurs; producing zygote
Fetal
Skin features: eyelashes, eyebrows, nails, hair development
Rapid growth, all organs functioning except the reproductive and some respiratory
Sex readily detected at 9-12 weeks
Embryo known as fetus until birth
Bone tissue begins to replace cartilage
Blood formation in bones begins