Exam 4 Review

Reproductive and Mammary SystemsAN S 214 Supplemental Instruction

4/24/13

Reproductive System Outline• Male Anatomy• Heat Regulation of Testes• Hypothalamic-Pituitary-Gonadal Axis• Spermatogenesis and Spermiogenesis• Female Anatomy • Ovarian Cycle• Uterine (Menstrual) Cycle• Hypothalamic-Pituitary-Gonadal Axis• Putting it All Together• Fertilization and Development• Pregnancy• Duct Formation• Abnormalities• Estrous Cycle• Seasonally Polyestrous

Male Anatomy• Seminiferous Tubules• Tubulus Rectus• Rete Testis • Efferent Ductules• Epididymis (Head, Body, Tail)• Ductus (Vas) Deferens• Seminal Vesicle

– Viscous alkaline seminal fluid– Fructose, ascorbic acid, coagulating enzyme, and

prostaglandins– 70% of the volume of semen

• Ejaculatory Duct • Prostate

– Milky, slightly acid fluid – Contains citrate and enzymes

• Bulbourethral (Cowper's) gland– Prior to ejaculation-thick, clear mucus– Lubricates the glans penis– Neutralizes traces of acidic urine in the

urethra• Urethra• Glans Penis

• Seminal fluid + Sperm = Semen

Heat Regulation of Testes

• Keeps testes 3 degrees Celsius cooler than body temperature

• Pampiniform Plexus– Countercurrent heat exchanger

• Cools arterial blood, warm venous blood

• Tunica Dartos Muscle – Smooth muscle that wrinkles scrotal skin

• Cremaster Muscle– Skeletal muscle that raises or lowers testes

Hypothalamic-Pituitary-Gonadal Axis

• Leydig/Interstitial Cells– Stimulated by LH– Secrete androgens

• Testosterone

• Sertoli/Sustenacular Cells– Stimulated by FSH– Nourishment of developing spermatozoa– Form blood-testes barrier– Produce inhibin-represses FSH– Secrete androgen-binding protein (ABP)– Produce mullerian duct-inhibiting

substance (MIS)

• Anabolic Steroids– Exogenous testosterone – Negative feedback on pituitary – Results in infertility, testicular atrophy and

impotence

Spermatogenesis and Spermiogenesis

• Spermatogonium-Most primitive cell– Mitosis

• Spermatogonium A– Mitosis

• Spermatogonium B– Mitosis

• Primary Spermatocytes– Meiosis I

• Secondary Spermatocytes– Meiosis II

• Spermatids

Differentiation • Spermatozoa

– Mature Sperm

Spermatogenesis

Spermiogenesis

Female Anatomy• Path of Oocyte

– Ovary– Oviduct

• Infundibulum• Ampulla• Isthmus

– Uterus– Cervix– Vagina

• External Genitalia– Clitoris– Labia minora– Labia majora– Accessory glands

Ovarian Cycle• Follicular Phase

– Primordial Follicle– Primary Follicle

• One layer of granulosa cells

– Secondary Follicle• Two layers of granulosa cells

– Tertiary Follicle, Late Secondary Follicle, or Antral Follicle• Three layers of cells-One being granulosa cells, Two of

thecal cells• Antrum begins to form

– Dominant Follicle, Mature Follicle, Graffian Follicle, or Vesicular Follicle• Meiosis occurs• Large antrum

• Ovulation – Secondary oocyte expelled

• Luteal Phase – Corpus Hemorrhagicum

• “Bloody Body”

– Corpus Luteum• “Yellow Body”

– Corpus Albicans• “White Body”

Uterine (Menstrual) Cycle• Menstrual Phase

– Days 1-5– Menstrual flow due to low

hormone levels• Proliferative Phase

– Days 6-14– Estrogen levels prompt new

endometrium in uterus• Secretory Phase

– Days 15-28– Progesterone levels prompt

further development of endometrium

– Glandular secretions

Hypothalamic-Pituitary-Gonadal Axis

• FSH stimulates Granulosa (G) cells to produce Estrogens

• LH stimulates Thecal (T) cells to produce androgens

• Estrogen Production– Cholesterol Progesterone

(G&T) Testosterone (T) –Aromatase (G)Estradiol (G)

Putting it All Together

Fertilization and Development• Aided by surface hyaluronidase enzymes, a sperm weaves its way past

granulosa cells of the corona radiata• Binding of the sperm to ZP3 molecules in the zona pellucida causes rise

in calcium levels within the sperm, triggering the acrosomal reaction• Acrosomal enzymes digest holes through the zona pellucida clearing a

path to the oocyte membrane • The sperm forms an acrosomal process, which binds to the oocyte’s

sperm-binding receptors• The sperm and oocyte plasma membranes fuse, allowing sperm

contents to enter the oocyte• Entry of sperm contents causes a rise in the calcium levels in the

oocyte’s cytoplasm, triggering the cortical reaction. The result is hardening of the zona pellucida and clipping off of sperm receptors (slow block to polyspermy)

• After the sperm penetrates the secondary oocyte, oocyte completes meiosis II forming ovum and second polar body

• Sperm and ovum nuclei swell, forming pronuclei• Pronuclei approach each other and mitotic spindle forms between them• Chromosomes of pronuclei intermix. Fertilization is accomplished

(Zygote is formed). Then the DNA replicates in preparation for the first cleavage stage.

• 4 cell stage • Morula• Blastocyst

– Implants roughly 7 days after ovulation

Pregnancy• Hormones

– Estrogen produced by corpus luteum and placenta• Causes uterine, mammary duct, and breast enlargement

– Progesterone produced by corpus luteum and placenta• Prevents menstruation, thickens endometrium and breast development

• Maternal recognition of pregnancy produced by blastocyst– Human- Human Chorionic Gonadotropin– Sow- Estrogen– Mare- Small Unknown Peptide– Cow- Bovine Interferon tau– Ewe- Ovine Interferon tau

• Organ development in utero– ~8 week cutoff for major malformations

Duct Formation• Wolffian (Mesonephric) Ducts

– Sex-determining region on Y (SRY gene)

– Male– Testosterone promotes

development– Mullerian inhibiting substance

(MIS) regresses mullerian ducts• Can cause freemartin in female twin

• Mullerian (Paramesonphric) Ducts– Female– Absence of testosterone, wolffian

ducts regress– Absence of MIS, mullerian ducts

develop

Abnormalities

• Male Pseudohermaphrodite– Genotype: XY– Phenotype: Testes inside body, female external genitalia– Caused by: Androgen Insensitivity Syndrome (AIS)

• Female Pseudohermaphrodite – Genotype: XX– Phenotype: Have ovaries, male external genitalia– Caused by: Congenital Adrenal Hyperplasia

• Adrenal glands overproduce testosterone

Estrous Cycle

• Anestrous– Without cyclicity

• PGF2α– Produced by endometrium when no pregnancy occurs– Regress Corpus luteum– Controls when the animal will cycle

Days in Cycle Stage of Cycle Phase Ovarian Structure Hormone Pattern 17-20 Proestrus Follicular Growing follicles

Corpus albicans↑Estrogen↓Progesterone

0-1 Estrus Follicular Graffian follicle, Dominant follicle, Mature follicle, or Vesicular follicle

Max. EstrogenMin. Progesterone

2-4 Metestrus Luteal Corpus hemorrhagicum

↓Estrogen↑Progesterone

5-16 Diestrus Luteal Corpus luteum Min. EstrogenMax Progesterone

Seasonally Polyestrous• Goal

– Give birth in spring when food is abundant

• Short day – Sheep– 5 month gestation– Breed in the fall– ↓Light ↑Melatonin ↑GnRH Cyclicity

• Long day – Horse– 11 month gestation– Breed in the spring– ↑Light ↓Melatonin ↑GnRH Cyclicity

Mammary System Outline

• Alveolus• Lactation Phases• Milk Synthesis and Letdown• Milk Components

Alveolus• Smallest unit of mammary• Composed of epithelial cells

– Produce milk components – Polar in nature

• Nucleus located near basal membrane

• Golgi apparatus near lumen of alveolus

• Myoepithelial cells contract to release milk contents

• Many alveoli make a lobule, many lobules make a lobe

Lactation Phases

Phase of lactation What is occurring… Important hormones Other details…Mammogenesis Preparation of breasts Duct Growth: E2, GH, GC Breast development

begins in uteroLobuloalveolar Growth: E2, GH, GC, P4, PRL

Lactogenesis Synthesis and secretion of milk components

PRL PRL causes synthesis of milk components in epithelial cells

Galactokinesis Milk ejection Oxytocin Oxytocin causes contraction of myoepithelial cells

Galactopoiesis Maintenance of lactation PRL PRL surge with sucklingPRL inhibits GnRHrBST (GH) can sustain lactation

Milk Synthesis and Letdown

Negative

Milk Components• Water• Carbohydrates

– Least variable milk component– Mainly lactose– Lactose intolerance is when people lack lactase

• Fat– Most variable milk component – Mainly Triglycerides

• Protein– Between carbohydrates and fats for variability– Whey (20%) – Casein (80%)

• Precipitates from whey at pH 4.6 by chymosin or rennin

• Vitamins and Minerals• Immunity • Growth Factors