Reproduction Female

The reproductive system of female mammals consists of the: –ovaries, –oviducts, –uterus, –vagina, and – external genitalia (vulva, etc).

Overview The compact ovary contains thousands of ovarian follicles, of which a few at a time rapidly go through several stages of maturation before ovulation. The ova is transported to the uterus via the oviduct where, if fertilized, it implants, forms a placenta, develops, and is delivered via the vagina.

Overview-continued The entire duct system is lined by epithelia with regional specializations. There are a variety of species differences in the shape of the uterus, and the type of placentation that supports the embryo. In contrast to the male, the urinary tract uses separate ducts until reaching the vestibule of the vagina.

Mammal, female The mammalian female reproductive tract consists of paired ovaries and a multi-part duct system.

Vestibule The vestibule is the terminal part of the duct system. It is shared with the urinary system

Vagina The vagina is a thick-walled fibromuscular tube that extends from the cervix to the vulva. The walls consist of a mucosa, muscularis, and adventitia.

The urethra from the urinary bladder joins with the reproductive duct in female mammals.

Cervix The cervix is a muscular valve which separates the vagina from the uterus. It may produce a mucus plug during infertile periods.

Uterus - body The body of the uterus is the site of implantation and development in primates.

Uterine horns Uterine horns provide additional space for the young to implant and develop. The length of the uterine horns varies between species, and may be nearly absent in primates.

Oviduct (fallopian tube) The uterine (fallopian) tube carries the ova to the uterus.

Infundibulum The infundibulum is the initial part of the duct system

Ovaries The ovaries are the female gonads. They produce the ova.

Ovaries Produce 1 ova per cycle in cow Produces ova per cycle in sow Produces 1-3 ova per cycle in ewe

The bovine uterus has two horns. Both ovaries are shown and the one on your left has a corpus luteum present. Developing follicles may be seen as little bumps on the surface of the ovary on the right.

Uterus The uterus, with layers called endometrium, myometrium and perimetrium, respectively.

Cervix CERVIX. The cervix acts as the valve of the reproductive tract. It separates the vagina from the uterus and is usually closed except during estrus and parturition.

Ovaries OVARY/FOLLICLE. The two ovaries in mammals are the site of oogenesis, production of the female gametes. In most mammals the OOGONIA have formed primordial follicles at the time of birth. These primordial follicles will go through several developmental stages until a mature follicle ruptures, expelling the ovum. The ovaries also produce hormones important to reproductive cyclesand pregnancy.

Ovary (canine)

Primordial follicles

Primary follicles

The PRIMARY FOLLICLE develops from the primordial follicle and is characterized by several layers of follicular cells surrounding the oocyte. The follicular cells become more cuboidal and secretory in appearance and are referred to as granulosa cells. At this time, a clear layer of extracellular material, called the zona pellucida, can be seen around the oocyte.

PRIMORDIAL FOLLICLE. In most mammals the OOGONIA have formed primordial follicles at the time of birth. It is generally believed that all of the primordial follicles that are going to develop are present at the birth of the animal. The primordial follicle is a single egg or oocyte surrounded by a single layer of flattened cells called the follicular cells. Many of the follicles will not develop and will undergo a gradual breakdown or atrophy: this process is called atresia and the follicles are said to be atretic.

Secondary follicles

SECONDARY FOLLICLES develop from primary follicles and are characterized by the formation of an antrum. –The antrum is a fluid-filled space which begins as a number of small spaces between the granulosa cells. –As the several spaces unite into a single fluid-filled chamber, the oocyte remains on a mound of granulosa cells, the cumulus oophorus, to one side of the follicle. –A layer of granulosa cells remains surrounding the oocyte. –The cells secrete the female sex steroids.

Regressing CL’s The corpus luteum forms from the cells of the theca interna and the granulosa cells under the influence of the pituitary luteinizing hormone.

Blood vessels and connective tissue grow into the luteal cells to form an endocrine gland which secretes progestins. Hormones from the corpus luteum will support fetal development during pregnancy. Afterwards it will become a scar (corpus albicans).

Bovine ovary, with CL

Bovine ovary - medium & high magnification

Estrous Cycle Begins with puberty Prepares the female for pregnancy 4 periods to cycle –Proestrus –Estrus –Metestrus –Diestrus

Proestrus –follicular development from FSH –Estrogen increasing

Estrus Female sexually receptive (standing heat) estrogen levels high length ~ 12 hrs to several days surge of LH & FSH Ovulation late or following estrus

Metestrus CL (corpus luteum) forms Produces progesterone

Diestrus If pregnanacy occurs, CL remains –progesterone high if no pregnancy, prostaglandin from uterus causes CL regression

Species cycle heat time of time to d hr ovulation mate Cow hr post-E 4-8 after E END Sow h after 1st d & again 2nd start of estrus Ewe h after start after start Goat h after start alternate days Mare d before to 1 d alternate days after estrus

Estrous Cycle Review Development of Follicle from FSH Ovulation, from LH surge CL Develops –progesterone –keeps animal preg. CL regresses –to corpus albicans –cycle begins again ANESTRUS –period of no cycling Polyestrous vs seasonally polyestrous –cow vs sheep

HORMONES - review –GnRH hypothalamus controls LH & FSH –FSH stimulates follicle –LH triggers ovulation & CL –Estrogen from follicle, prepares for preg. Progesterone –from CL –prevents further cycling –maintains pregnancy Prostaglandin (Pf 2  ) –regresses CL

PREGNANCY Length of Pregnancy, days –cow 282, 9 mo, 12 days –sow 114, 3 mo, 3 wk, 3 days –ewe 150, 5 mo –mare 336, 11 mo +

Sperm combines with ovum ONLY 1 sperm can enter ovum Cell divisions start –sometimes split, forming identical twins Fertilization takes place in oviduct Fertilized ovum moves down to uterine horn (or uterus) for implantation

Placentation After implantation into the uterine endometrium, the developing embryo becomes surrounded by the chorionic, amniotic, and allantoic membranes. In fish and birds these same membranes allow diffusive exchange of of CO2 and O2 with the environment, while nutrients are provided by the yolk sac.

In mammals, nutrients and wastes are exchanged with the maternal circulation across a specialized region of these these membranes called the placenta. The placenta provides a large surface area of close association between the two independant circulations for diffusive and carrier mediated exchange.

In addition the placenta produces hormones to support the pregnancy. The gross arrangement of the placenta may be diffuse, zonary discoid, or cotyledonary, depending on the species.

Bovine placenta Allantoic sac Amniotic sac

Bovine placenta

Fetal cotyledons are seen on the surface of the chorioallantoic membrane which attach to the maternal caruncles (maternal cotyledons) to provide for gas and nutrient exchange. The fetal cotyledon is shown here with villi, which develop off the surface of the chorio-allantoic membrane and grow into sulci of the maternal caruncle.This interdigitation is the site of blood gas and nutrient exchange. (There is no mixing of blood between the fetus and the mother.)

Parturition (giving birth) Placenta produces more estrogen Causes prostaglandin from uterine wall Regression of CL, reduced progesterone RELAXIN causes pelvic muscles, ligaments to ‘loosen’ PROLACTIN stimulates milk synthesis Oxytocin stimulates & strenghtens uterine contractions

Difficulties at Birth Orientation at birth –rear first –one leg back –head twisted –too large –inadequate contraction strength –too long a birth process stillborn Membranes cover nose, prevent breathing Retained placenta Abnormal bleeding Premature births

Female Reproduction Review The ovaries contain a large number of follicles, of which a few rapidly mature during each cycle. The theca and granulosa cells proliferate as each follicle develops from a primordial, to primary, to secondary, to mature follicle (Graafian) which releases the oocyte and then transforms into a corpus luteum and later a corpus albicans.

The ova move into the first part of the uterine tube (oviduct, fallopian tube) where fertilization may take place. Implantation and embryo development occurs in the uterus which has a nourishing, glandular epithelia (endometrium) surrounded by smooth muscle (myometrium). The uterus of some species have elongated horns or a dividing septum.

The placenta developes from portions of the fetal membranes (chorion, amnion and allantois) that contact the endometrium. The close association of the independent maternal and fetal blood supplies allows diffusive exchange of nutrients and wastes.

The muscular cervix separates the uterus from the vagina, and produces a thick mucus. If pregnancy results, the CL remains and produces progesterone, maintaining pregnancy. If not, the CL regresses and the cycle begins anew.

Repro in BIRDS The form of the reproductive tract of female birds is in some ways simlar to that seen in mammals: ova produced in the ovary are fertilized in the proximal oviduct and progress though the uterus and vagina.

As in mammals the oviduct is lined by an epithelia surrounded by smooth muscle. However the function of various portions of the tract are quite different from mammals.

Along the various parts of oviduct the different componants of the eggshell are formed. The process takes about 25 hours in a chicken. The completed egg with shell is passed to the outside world via the cloaca, the shared terminal portion of the reproductive, urinary and gastrointestinal tracts.

Embryo development largely occurs outside the mother. Gaseous exchange occurs through the shell while nurients are provided by the yolk.

1. Infundibulum 2. Ovary 3. Ovum 4. Magnum 5. Isthmus 6. Uterus 7. Vagina 8. Cloaca

The egg is in the isthmus for about 1.5 hours where it receives the shell membranes. The egg occupies the uterus for about 20 hours. During the first 8 hours most of the activity is the addition of water, leading to a doubling of the weight of the albumen. During the last 12 hours, the shell is calcified by the secretion of calcium from the glands.

It takes about 24 hours for an egg to travel from the infundibulum to the vagina. The vagina has a muscular wall. Their purpose is to move the egg rapidly out of the reproductive system.

Bird male The proximal portions of the male bird reproductive system is quite similar to mammals. It consists of testes containing seminferous tubules which produce sperm with the help of interstitial and sertoli cells. The spermatozoa travel via efferent ductules to the epididymis,and then on to the ductus deferens.

The bird is different from most mammals in that the testes are located in the abdominal cavity (and therefore subject to the high body temperature of birds). In addition, the bird lacks a penis; the ductus deferens deliver sperm to the cloaca, which are transfered to the vagina during mating.

Bird Reproduction Review The female bird has a single functional ovary which produces the ova. The oviduct consists of five parts. Fertilization occurs in the infundibulum, where sperm are stored. The protein coat of the egg is added during the 3 hour passage through the magnum. The shell membranes are added by the keratin secreting glands of the isthmus. Water is added and the shell is calcified during the 20 hours spent in the uterus. The vagina adds a waxy coating and serves as a sperm storage site.

The testes of the male are within the abdominal cavity and operate at higher temperatures than those of most mammals. Each testes produces sperm in the seminiferous tubules under the influence of interstitial and sustentacular cells.

The sperm are transported via the efferent ductules, epididymes, and ductus deferens to the cloaca. The cloaca is a common terminal passage for the reproductive, urinary, and digestive tract in both male and female birds. The reproductive tract enters the cloaca at the urodeum.