ANSC 312 - Midterm 1 (Lectures 1-4)

Hormone

• A substance produced by one or more tissues/glands that is transported by the blood to exert a specific effect upon another organ 

Peptides, Glycoproteins, Steroids, Prostaglandins

4 Chemical Classes of Reproductive Hormones

Peptide Hormones

Chemical Class of Reproductive Hormones

• Amino acid based hormone

• Easy and quick to fabricate, just a few aa

Glycoproteins

Chemical Class of Reproductive Hormones

• Amino acid based hormone

• Polypeptide hormones that contain carbohydrate moieties

• Large and complex compared to peptide hormones

• More difficult to produce

• Need to be intact in order to properly interact with receptors

Steroids

Chemical Class of Reproductive Hormones

• Lipid-based hormone

• Various forms, but all have common molecular structure = 4 C rings labelled A, B, C, D

• Origin/base of these hormones is cholesterol

  • Goes through a series of enzymatic modifications to produce various types

Prostaglandins

Chemical Class of Reproductive Hormones

• Lipid-based hormone

• Fairly ubiquitous in biological systems, found throughout the body

• Consist of 20 C unsaturated fatty acids that are derived from arachidonic acid 

Steroid Pathway

• Any steroid starts out as cholesterol and goes through a series of enzymatic reactions

• Cholesterol can be converted to Pregnelolone

• Pregnelolone converted by enzymes to Progesterone

• Progesterone converted to Testosterone

• Testosterone (if there are the enzymes present) will be converted to Estradiol

• In order to get any of these steroid, the appropriate enzymes need to be present and in place to complete each conversion

Cholesterol, Pregnenolone, Progesterone, Testosterone, Estradiol

Steroid Pathway

1. Hormone-receptor binding (surface)

2. G-protein activation

3. Adenylate cyclase activation

4. Protein kinase activation

5. Synthesis of new product

5 steps of protein hormone action

1. Steroid transport (associated with carrier protein)

2. Movement through cell membrane and cytoplasm

3. Binding of steroid to nuclear receptor

4. mRNA and protein synthesis

4 Steps of Steroid Hormone Action

hypothalamus, pituitary, gonads, uterus, placenta

5 main sources of reproductive hormones

3rd ventricle in the middle of the brain, above the pituitary

Location of hypothalamus

Sella turcica

Location of pituitary gland

Portal vessels

Hypothalamus and pituitary are separated by _______

Allows for connection/communication network to allow hypothalamus to control the anterior pituitary and create hormones that end up in the posterior pituitary and are released from there

Hypothalamic-Hypophyseal System

Hypophyseal artery

• Transports blood coming in close to the hypothalamic neuron and hypothalamus and extending down into anterior pituitary

• Hypothalamus interacts with centers in the brain to detect what is going on in and around the body and in response will produce releasing hormones that go through ___________ into anterior pituitary

Hypophyseal vein

• Associate with anterior and posterior pituitary and carry blood/secretions away from those glands

• Releasing hormones stimulate other hormone production in the anterior pituitary which will be released, at the appropriate time, through the ____________ to the body

Gonadotropin Releasing Hormone (GnRH)

Reproductive Hormone

• Gland: hypothalamus

• Chemical class: Neuropeptide

• Target Tissues: Anterior Pituitary

• Action: Release of FSH and LH from anterior pituitary

• Hypothalamus

• Neuropeptide

• Anterior Pituitary

• Release of FSH and LH from anterior pituitary

Gonadotropin Releasing Hormone (GnRH)

• Gland:

• Chemical class:

• Target Tissues:

• Action:

Follicle Stimulating Hormone (FSH)

Reproductive Hormone

• Gland: anterior pituitary

• Chemical class: Glycoprotein

• Target Tissues: Male - Testis (Sertoli cells)

  Female - Ovary (Granulosa cells)

• Action: Male - Testis (Sertoli cell function)

  Female - Ovary (Follicle growth and Estradiol synthesis)

• Anterior pituitary

• Glycoprotein

• Male - Testis (Sertoli cells)

  Female - Ovary (Granulosa cells)

• Male - Testis (Sertoli cell function)

  Female - Ovary (Follicle growth and Estradiol synthesis)

Follicle Stimulating Hormone (FSH)

• Gland:

• Chemical class:

• Target Tissues:

• Action:

Luteinizing Hormone (LH)

Reproductive Hormone

• Gland: anterior pituitary

• Chemical class: Glycoprotein

• Target Tissues: Male - Testis (Leydig cells)

  Female - Ovary (Theca and Luteal cells)

• Action: Male - Testosterone synthesis

  Female - Ovulation and Progesterone synthesis

• Anterior pituitary

• Glycoprotein

• Male - Testis (Leydig cells)

  Female - Ovary (Theca and Luteal cells)

• Male - Testosterone synthesis

  Female - Ovulation and Progesterone synthesis

Luteinizing Hormone (LH)

• Gland:

• Chemical class:

• Target Tissues:

• Action:

Prolactin

Reproductive Hormone

• Gland: anterior pituitary

• Chemical class: Peptide

• Target tissues: Mammary Glands

• Action: Lactation and Maternal Behaviour

• Anterior pituitary

• Peptide

• Mammary Glands

• Lactation and Maternal Behaviour

Prolactin

• Gland:

• Chemical class:

• Target Tissues:

• Action:

Oxytocin

Reproductive Hormone

• Gland: posterior pituitary

• Chemical class: Neuropeptide

• Target Tissues: Male - Testicular (stimulates seminiferous tubules)

  Female - Uterus and Mammary

• Action: Male - Sperm Transport (by causing contractions)

  Female - Uterine contractions and Mammary cell growth and Milk letdown

• Posterior pituitary

• Neuropeptide

• Male - Testicular (stimulates seminiferous tubules)

  Female - Uterus and Mammary

• Male - Sperm Transport (by causing contractions)

  Female - Uterine contractions and Mammary cell growth and Milk letdown

Oxytocin

• Gland:

• Chemical class:

• Target Tissues:

• Action:

Glandular

Anterior pituitary has more ______ tissue

Neural

Posterior pituitary has more ______ tissue

Gonadotroph Cells

• Cells of anterior pituitary

• respond to GnRH and produce FSH and LH

Lactotroph cells

• Cells of anterior pituitary

• Produce prolactin

Herring Bodies

• Within posterior pituitary

• store and release oxytocin 

Estradiol (E₂)

Reproductive Hormone

• Gland: ovaries

• Chemical class: Steroid

• Target Tissues: Hypothalamus, Reproductive Tract, Mammary Gland

• Action: Female Sexuality

- ↑ Sexual Behaviour 

- ↑ GnRH Production 

- ↑ Uterine Activity 

- Mammary   

  Development

• Ovaries

• Steroid

• Hypothalamus, Reproductive Tract, Mammary Gland

• Female Sexuality

  - ↑ Sexual Behaviour 

  - ↑ GnRH Production 

  - ↑ Uterine Activity 

  - Mammary   

    Development

Estradiol (E₂)

• Gland:

• Chemical class:

• Target Tissues:

• Action:

Progesterone (P₄)

Reproductive Hormone

• Gland: Ovaries, Placenta

• Chemical class: Steroid

• Target Tissues: Hypothalamus, Uterine endothelium and myometrium, Mammary Gland

• Action: Pregnancy Maintenance

  - ↓ Sexual Behaviour 

  -↓ GnRH Production 

  -↓ Uterine Activity 

  - Lactation

• Ovaries, Placenta

• Steroid

• Hypothalamus, Uterine endothelium and myometrium, Mammary Gland

• Pregnancy Maintenance

  - ↓ Sexual Behaviour 

  -↓ GnRH Production 

  -↓ Uterine Activity 

  - Lactation

Progesterone (P₄)

• Gland:

• Chemical class:

• Target Tissues:

• Action:

Testosterone (T)

Reproductive Hormone

• Gland: Testis

• Chemical class: Steroid

• Target Tissues: Hypothalamus

  Reproductive Tract

  Muscle

• Action: Male Sexuality

  - ↑ Sexual Behaviour 

  - ↓ GnRH Production 

  - Spermatogenesis 

  - ↑ Muscle  

     Development

• Testis

• Steroid

• Hypothalamus

  Reproductive Tract

  Muscle

• Male Sexuality

  - ↑ Sexual Behaviour 

  - ↓ GnRH Production 

  - Spermatogenesis 

  - ↑ Muscle  

     Development

Testosterone (T)

• Gland:

• Chemical class:

• Target Tissues:

• Action:

Prostaglandin (E₂)

Reproductive Hormone

• Gland: Uterus

• Chemical class: Prostaglandin

• Target Tissues: Ovary

• Action: ↑ Progesterone Production

• Uterus

• Prostaglandin

• Ovary

• ↑ Progesterone Production

Prostaglandin (E₂)

• Gland:

• Chemical class:

• Target Tissues:

• Action:

Prostaglandin (F_2a)

Reproductive Hormone

• Gland: Uterus

• Chemical class: Prostaglandin

• Target Tissues: Ovary

  Uterine myometrium

• Action: ↓ Progesterone Production

  Stimulates Uterine Contractions (Parturition)

• Uterus

• Prostaglandin

• Ovary

  Uterine myometrium

• ↓ Progesterone Production

  Stimulates Uterine Contractions (Parturition)

Prostaglandin (F_2a)

• Gland:

• Chemical class:

• Target Tissues:

• Action:

Equine Chorionic Gonadotropin (eCG - horse)

Reproductive Hormone

• Gland: Placenta

• Chemical class: Glycoprotein

• Target Tissues: Ovary

• Action: Maintains Progesterone Production 

  **(FSH like activity in other species)

• Placenta

• Glycoprotein

• Ovary

• Maintains Progesterone Production 

  **(FSH like activity in other species)

Equine Chorionic Gonadotropin (eCG - horse)

• Gland:

• Chemical class:

• Target Tissues:

• Action:

Pineal Gland

• Located above the hypothalamus between the hemispheres of the brain 

• Plays a role in reproduction, particularly in livestock

• Sensitive to environmental light and senses changes in photoperiod 

• Releases melatonin in response to dark 

• _______ via melatonin regulates breeding activity in seasonal breeder (ex. sheep, goats, horses)

Broad Ligament

Structure of the Female Reproductive Tract

• Supports and houses the vascular supply, lymphatic drainage and nerves for the female tract

• Like the scaffolding that holds the female tract in position in the abdomen

Mesovarium

Portion of the Broad Ligament

• Supports the ovary

• Houses the vascular supply, lymphatic drainage and nerves for the ovary 

• Forms the ovarian stem = hilus

Hilus

• Ovarian stem

• Part of the mesovarium of the broad ligament

Mesosalpinx

Portion of the Broad Ligament

• Not very prominent

• Connects to oviduct

• Thin, transparent segment of the BL that supports the oviduct 

• Forms a pouch around the ovary = bursa

Bursa

• Pouch around ovary

• Part of the mesoalpinx of the broad ligament

Mesometrium

Portion of the Broad Ligament

• Majority of tissue

• Suspends uterus in abdomen from dorsal wall

• Largest portion of the BL 

• Supports the uterine horns – suspended from the dorsal body wall

Utero-ovarian ligament

• Attaches the ovary and uterus, but is not a part of the BL

Ovaries

Structure of the Female Reproductive Tract

• Production of oocytes (female contribution to embryo)

• Production of Estradiol 

• Production of Progesterone

primordial follicle, primary follicle, secondary follicle, tertiary follicle, antral (preovulatory) follicle, corpus luteum, corpus albicans

Order of follicle structures in development in ovary

Medulla

Center of ovary = _____

Cortex

Outside of ovary = ______

1. Theca cells respond to LH and produce testosterone

2. Testosterone migrates to granulosa cells

3. Granulosa cells respond to FSH and converts testosterone to estradiol

Steps of Estradiol (E2) Production by the Ovaries

1. Theca externa

2. Granulosa cells

3. Antrum

4. Theca interna

5. Basement membrane

6. Corona radiata

7. Oocyte

8. Cumulus oophorus

Label the parts of a mature pre-ovulatory (antral) follicle

serosa, muscularis (longitudinal, circular), submucosa, mucosa

Layers of the female tract (from outside to inside)

Serosa

Layer of the Female Tract

• Outer layer

• “Skin” of the tract

• Single layer of flatten cells that cover the female tract (like its skin)

Muscularis

Layer of the Female Tract

• 2nd layer

• Double layer of smooth muscles 

  • Outer longitudinal layer 

  • Inner circular layer 

• Allows tissues to contract (transport - sperm, oocyte, embryos)

Submucosa

Layer of the Female Tract

• 3rd layer

• Houses blood vessels, nerves and lymphatics 

• Supporting layer for the mucosa

Mucosa

Layer of the Female Tract

• 4th/innermost layer

• Lines the lumen

• Secretory layer of epithelium in lumen of the reproductive tract 

• Properties and role varies for each segment of the tract and depending on the endocrine environment

Oviducts

Structure of the Female Reproductive Tract

• Connection between the ovaries and the rest of the reproductive tract

• Gamete/Embryo Transport 

• Site of Fertilization

infundibulum, ampulla, ampullary-isthmic junction, isthmus, uterotubal junction

Segments of the Oviduct (from closer to the ovary to further)

Infundibulum

Segment of the Oviduct

• Thin funnel shaped opening closes over the ovary 

• Forms “pocket” around the ovary (helps to cover ovary)

• When ovary have oocytes that ovulate, end up in this pocket

• Fimbriae “finger-like projects sweep oocytes toward the oviduct"

• Tissue that interacts with ovary and helps to intercept any oocytes that are ovulated

Ampulla

Segment of the Oviduct

• “Upper-half” of the oviduct

• Large diameter and ciliated mucosa to transport oocytes to the point of fertilization

Ampullary-isthmic junction

Segment of the Oviduct

• Transition between ampulla and isthmus

• Site of Fertilization

  • Oocyte doesn’t sit and wait here for fertilization, fertilization will occur at some point when moving from ampulla to isthmus

Isthmus

Segment of the Oviduct

• “Lower-half” of the oviduct attached to the uterus 

• Small diameter tube that transports sperm to AIJ & transports embryos to the uterus

Uterotubal junction (UTJ)

Segment of the Oviduct

• Junction of the uterus & oviduct 

• Sperm reservoir

Uterus

Structure of the Female Reproductive Tract

• Sperm transport 

• Maintains and nourishes embryo and fetus

• Role controlled by stage of the female cycle (dynamic, and susceptible to endocrine events)

  • Sperm transport to the oviduct 

  • Maintain pre-implantation embryo 

  • Maternal portion of placenta – transfer of nutrients to fetus 

  • Expulsion of fetus and fetal placenta

Perimetrium

Uterine Tissue Layer - Serosa

• External layer that connects to the mesometrium of the broad ligament

Myometrium

Uterine Tissue Layer - Muscularis

• Muscle layers of the uterus 

• Facilitates uterine contractions 

  • Sperm transport (post-coital) 

  • Expulsion of fetus & placenta (parturition)

Endometrium

Uterine Tissue Layer - Submucosa and Mucosa

• Cells lining the uterine lumen 

• Roles vary with female cycle 

  • Secretions that enhance sperm and embryo survival 

  • Signals if pregnancy has been achieved 

  • Maternal portion of placenta & transfer of nutrients to fetus

Duplex uterus

Type of Uterus

• 2 cervical entries

• In rabbit - cervical entry for each uterine horn, can have sperm from 1 buck on one side, and another on the other side

• Marsupials - branched cervix leading up to uterine horn

Bicornate uterus

Type of Uterus

• Distinct uterine horns

• Can be poor to moderately developed or highly developed

• Very long and developed uterine horns in litter-bearing species compared to monocorpus species

Simplex uterus

Type of Uterus

• No defined uterine horns

• Simply uterine body

• Primates

Caruncles

Variation in Endometrium

• in ruminants, points of attachment of uterus to placenta

• On surface of endometrium

Endometrial folds

Variation in Endometrium

• creates increased surface area that placenta interacts with

Cervix

Structure of the Female Reproductive Tract

• Thick walled segment of female system that separated the internal tract (sterile portion) from the external tract (non-sterile)

• Transition tissue between uterus and vagina

• Prevents microbial contamination of uterus (considered sterile)

• Site of semen deposition (sow, mare) 

• Semen reservoir/sperm transport

Single Fold	Bitch and Queen
Multiple Folds	Sow, Ewe, Cow, and Mare

Functions:

Copulation

• Reservoir/Barrier to sperm transport (make sure only better sperm get in)

• Site of semen deposition

Pregnancy

• Mucus plug conserves the sterile uterine environment (without plug, concerns for infection)

Vagina

Structure of the Female Reproductive Tract

• Organ of copulation 

• Site of semen deposition (cows, ewes, queen, bitch) 

• Birth canal

• External portion of the reproductive tract

• Copulatory organ of the female 

  • Site of semen deposition (Cow, Ewe, Bitch & Queen) 

• Thickness & Secretions of the mucosa influenced by estrus cycle 

  • Whether dominant steroid is progesterone or estradiol that will cause secretions by the mucosa that acts as a lubricant

  • When animal is copulating - there will be high levels of estradiol 

  • Lubricate and protect the vaginal wall

lower abdomen, below rectogenital pouch

Position of reproductive tract

Monotocous

Term for animals that produce a single offspring at birth

Polytocous

Term for animals that produce multiple offspring at birth (litter-bearing)

Ectoderm

Embryonic Germ Layer

Reproductive Tract 

- ♀ vagina (external) or ♂ penile sheath 

- ♀ clitoris or ♂ penis 

Nervous System 

- hypothalamus 

- anterior & posterior pituitary 

Oral cavity 

Nasal cavity

Mesoderm

Embryonic Germ Layer

Reproductive System

- gonads (ovaries/testes) 

- ♀ uterus, cervix, vagina(internal) 

- ♂ epididymus, ductus deferens, ♂ accessory sex glands 

Urinary System 

Skeletal System 

Blood Vessels 

Muscle

Endoderm

Embryonic Germ Layer

Digestive System 

Respiratory System 

Glandular Systems

1. Development of hypothalamic-hypophyseal systems 

2. Migration of primordial germ cells from the yolk sac 

3. Sex cords development in the gonad & mesonephric renal system regression/transformation 

4. Sexual Differentiation - Sex becomes evident from structures 

5. Development of female tract and ovaries 

6. Formation of the broad ligament

6 major events of embryonic development of the female reproductive system

280-290 days / 9.5 months

Cattle Gestation Period

145-150 days / 5 months

Sheep Gestation Period

114 days / 3 months, 3 weeks, 3 days

Swine Gestation Period

60-65 days / 9 weeks

Dog Gestation Period

63-67 days / 9 weeks

Cat Gestation Period

Rathke’s pouch

Anterior pituitary develops from the _________ during embryonic development

Infundibulum

Posterior pituitary develops from the _________ during embryonic development

pronephros → mesonephros → metanephros

3 embryonic renal systems in order

Pronephros

First Embryonic Renal System

Most primitive form of kidney found in the developing embryo – limited function & eventually degenerates

Mesonephros

Second Embryonic Renal System

• These early kidneys (pick up from pronephros) of early mammalian embryo eventually regresses and gives way to the Metanephros 

• Remnants of the regressing _______ renal system become portions of the reproductive tracts

• When no longer acting as renal system, becomes part of reproductive system

Metanephros

Third/Final Embryonic Renal System

Renal system that will eventually become the functioning kidneys in the adult animal

Paramesonephric/Mullerian ducts

Ducts that develop into the female reproductive tract during embryogenesis