Female Reproduction

Female Reproduction

I.	Function of the Female

	1.	The production of Ova
	2.	Provide an environment for growth and nutrition 
		of the fetus that develops after fertilization
		A.	Give Birth
		B.	Continue nutritional function through lactation

II.	Female Reproductive Organs

	1.	Ovary
		A.	Produce the Ovum
			a.	Follicle
				--Rupture Ovulation
		B.	Produce Female Sex Hormones
			a.	Follicular cells
				i.	Granulosa cells
					--Estrogens
				ii	Theca cells
					--Progesterone
		C.	Maintain Pregnancy
			a.	Corpus Luteum
				i.	Progesterone
		D.	Ovary (and Testis) under the control 
			of endocrine glands in the brain
			a.	Hypothalamus
				i.	Gonadotropin Releasing Hormone 
					(GnRH)
					--Causes release of Gonadotropins 
						from Pituitary
					--Controlled by Female Sex Steroids (Feedback)
			b.	Pituitary
				I.	Follicle Stimulating Hormone (FSH)
					--Stimulates Follicle Development 
						and Growth
				ii.	Luteinizing Hormone (LH)
					--Required for Ovulation
					--Corpus Luteum Formation
	2.	Oviduct
		A.	Site of Fertilization
			a.	Haploid sperm and egg fuse Diploid zygote
	3.	Uterus
		A.	Site of Embryo and Fetal Development
		B.	Produces Prostaglandin if not Pregnant
			a.	Causes Luteolysis
	4.	Cervix
		A.	Barrier
			a.	Selectively lets sperm in uterus 
				and oviducts
			b.	Closed or sealed during pregnancy
		B.	Expulsion of Fetus
	5.	Vagina
		A.	Female Copulatory Organ
		B.	Birth Canal
	6.	Vulva
		A.	Opening to female reproductive tract

III.	Endocrinology of Female Reproduction

	1.	Steroid hormones
		A.	Produced in Ovary, Placenta, and Adrenal Gland 
			(Testis in male)
			a.	All steroid hormones are derived from 
				cholesterol
			b.	Biosynthesis Pathway
				I.	Cholesterol (27 carbon)
				ii.	Pregnenolone (21 carbon)
				iii.	Progesterone (21 carbon)
				iv.	Testosterone (19 carbon)
				v.	Estrogen (18 carbon)
			c.	Estrogen and Progesterone are the most 
				important in female reproduction	
	2.	Estrogens
		A.	Produced by primarily by granulosa cells 
		B.	Also produced by Placenta, and Adrenal Gland
		C.	General Function
			a.	Cellular Proliferation and Growth of 
				tissues related to Reproduction
		D.	Specific Functions
			a.	Stimulate endometrial gland growth
			b.	Stimulate duct growth in the mammary gland
			c.	Increase secretory activity of the 
				reproductive ducts
			d.	Initiation of sexual receptivity
			e.	Regulation of LH and GnRH by the anterior 
				pituitary and hypothalamus
			f.	Possible regulation of Prostaglandin F2 alpha 
				by the nongravid and gravid uterus (pigs)
			g.	Early union of the epiphysis with the 
				shafts of long bones, ceasing growth of 
				long bones
			h.	Protein anabolism
			i.	Vaginal epithelium proliferation and 
				cornification
	3.	Progesterone
		A.	Produced in Corpus luteum, Luteal cells, Granulosa 
			cells, Placenta, and Adrenal Cortex
		B.	Perform many functions in concert with estrogen 
			and usually requires estrogen priming
		C.	Functions
			a.	Promotion of endometrial gland growth
			b.	Stimulation of secretory activity of the 
				oviduct and endometrial glands to provide 
				nutrients for the developing embryo prior 
				to implantation
			c.	Promotion of alveolar growth inn the 
				mammary gland
			d.	Prevention of contraction of the uterus 
				during pregnancy
			e.	Regulation of secretion of gonadotropins	
	4.	Gonadotropins
		A.	FSH
			a.	Functions
				i.	Promotion of follicular growth
				ii.	Stimulate granulosa cell steroid 
					production
		B.	LH
			a.	Functions
				i.	Ovulation
				ii.	Stimulation of theca cell steroid 
					production
				iii.	Causes Luteinization (CL formation)
	5.	Negative Feedback
		A.	Estrogen and Progesterone
			a.	Feedback on hypothalamus and pituitary 
				to decrease FSH and LH production
		B.	Inhibin
			a.	Produced by Granulosa cells
			b.	Feedback on pituitary to decrease FSH only
		C.	Activin
			a.	Produced by Granulosa cells
			b.	Feedback on pituitary to increase FSH only
	6.	Positive Feedback
		A.	Estrogen will increase because of production 
			by preovulatory follicles 		
		B.	Threshold level will cause a burst of GnRH release 
			by the hypothalamus
		C.	GnRH burst will cause a spike in LH release
			i.	Signal for ovulation

IV.	Oogenesis and Folliculogenesis

	1.	Oogenesis
		A.	The process involved in the transformation 
			of germinal epithelial cells 
			(stem cells) to ovum (egg)
		B.	Mitosis and Meiosis 	
			a.	Oogonia
				i.	Undergo mitosis
				ii.	Occurs during fetal development
			b.	Oocytes
				i.	Primary oocyte arrests in meiotic 
					prophase I
				ii.	Occurs during fetal development
				iii.	Meiosis is reestablished at Puberty
			c.	Ovum
				i.	Only one ovum is produced from 
					a primary oocyte (4 sperm are 
					produced from a primary spermatocyte)
				ii.	Three polar bodies develop instead
					--Contain genetic material but lack 
						cytoplasm
	2.	Folliculogenesis
		A.	Differentiation and growth of the follicle
			a.	In concert with oogenesis
		B.	Follicular waves occur during estrus cycle 
			(see below)
			a.	Phases
				i.	Primary follicle
					--One layer of granulosa cells
				ii.	Secondary follicle
					--Multiple layers of granulosa 
						cells
				iii.	Tertiary follicle
					--Antrum formation
				iv.	Graafian follicle
					--Preovulatory follicle
			b.	Many of the follicles (and their oocytes) 
				undergo atresia
				i.	Atresia is caused by apoptosis			

V.	Reproductive Cycles

	1.	Puberty
		A.	Sexual Maturity
		B.	Ability to Mate and Produce Offspring
		C.	Caused by maturation of the hypothalamus
			a.	Ability to react to feedback mechanisms
		C.	Age of Puberty
			a.	Cattle = 12 months
			b.	Swine = 6-7 months
			c.	Sheep = 6-7 months
			d.	Horses = 15-18 months
		D.	Maximum Sexual Maturity happens later
	2.	Estrous Cycle
		A.	Regular Periods of Sexual Receptivity (Estrus)
		B.	Stages
			a.	Estrus (or Heat)
				i.	Sexual Receptivity
					--Caused by Estrogens
				ii.	Ovulation
					--Caused by LH spike
			b.	Luteal Phase
				i.	Corpus Luteum on Ovary
				ii.	Progesterone concentrations rise
			c.	Follicular Phase
				i.	Corpus Luteum Regresses
					--Prostaglandin F2 
				ii.	Follicles Develop
				iii.	Estrogen concentrations rise
			d.	Estrus
		C.	Duration and Frequency of Heat and Time of Ovulation

Farm		Length of	Duration of 	Time of 
Species		Estrous Cycle	Estrus		Ovulation

Cattle		21 days		12 hours	30 hrs after start of estrus
Pigs		21 days		44 hours	34 hrs after start of estrus
Sheep		17 days		30 hours	26 hrs after start of estrus
Horses		21 days		6 days		1 day before end of estrus
	
		D.	Seasonal Breeders
			a.	Horses and Sheep
			b.	Have estrous cycles only certain periods 
				of the year
			c.	Pineal Gland
				i.	Secretes Melatonin
				ii.	Effects Hypothalamus
			d.	Sheep
				i.	Breeding season in Fall 
					(Shorter Days)
				ii	Anestrus Spring and Summer
			e.	Horses
				i.	Breeding season in Spring 
					(Longer Days)
				ii.	Anestrus Fall and Winter
	3.	Pregnancy
		A.	Fertilization
			a.	Sperm must undergo Capacitation
				i.	Maturation to ready for 
					penetration of egg
			b.	Occurs in Oviduct
		B.	Period of the Embryo
			a.	Migration to Uterus (3-4 days)
			b.	Stages
				a.	One Cell Zygote
				b.	Cleavage
					--Division without an increase 
						in size
				c.	Morula
					--Last Cleavage Stage
				d.	Blastocyst
					i.	Fluid filled cavity 
						(Blastocoel)
					ii.	Trophoblast
						--Become Placental 
							Membranes
					iii.	Inner Cell Mass
						--Becomes Embryo Proper
				e.	Gastrulation
					i.	First stage of organogenesis
					ii.	Division into three germ 
						layers
						--endoderm, mesoderm, 
							ectoderm
			C.	Maternal Recognition of Pregnancy
				a.	Occurs day 12 to 21 after 
					fertilization depending on species
				b.	Factors produced by embryo inhibit 
					Prostaglandin production by uterus
			D.	Implantation
				a.	Embryo attaches to Uterine Lining
			E.	Placentation
				a.	Formation of the Placenta
				b.	Functions
					i.	Nutrition
					ii.	Protection
						1.	Physical
						2.	Immunological
					iii.	Waste Storage
					iv.	Endocrine function
						--Produces progesterone and
							other hormones to 
							maintain pregnancy
				c.	Extraembryonic Membranes
					i.	Yolk sac
						--Vestigial (Waste)
					ii.	Amnion
						--Fetal Protection
					iii.	Allantois
						--Fetal Blood Supply
					iv.	Chorion
						--Outer layer
						--Maternal Link
					v.	In farm animals, Chorion 
						& Allantois fuse
						--Chorioallantoic 
							Placentation
				d.	Chorionic Villi
					i.	Connection between fetus 
							& mom
					ii.	Types
						--Diffuse = Pig
						--Diffuse (microcotyledonary) 
							= Horse
						--Cotyledonary 
							= Sheep & Cattle
						--Zonary = Dog & Cat
						--Discoid = Humans & Monkeys
				e.	Placental Circulation
					i.	Umbilical Cord
					ii.	Linked to allantoic vessels
					iii.	Vascular link between Mother
							& Fetus
			F.	Period of the Fetus
				a.	Much of Organogenesis has occurred
				b.	Conceptus looks like species
				c.	Growth Stage
			G.	Parturition
				a.	Process of Birth
				b.	Signaled by Fetus
				c.	Stages
					i.	Dilation of cervix
					ii.	Expulsion of Fetus
					iii.	Expulsion of Placenta
				d.	Difficult Birth = Dystocia
			H.	Gestation Lengths and 
				Usual Number of Offspring

Farm Species		Length		Number of Offspring

Cattle			285 days		1 calf (1-3.5% Twins)
Swine			114 days		6-14 piglets
Sheep			147 days		1-3 lambs
Horses			336 days		1 foal (1-2% Twins)	
			
			I.	Uterine Involution
				a.	Uterus must recover from pregnancy 
					before it can become pregnant again
				b.	Uterus shrinks
					i.	Apoptosis
				c.	Endometrium heals
				d.	Myometrium contracts