Endocrine System Notes PDF

Endocrine System Endocrine System ACTIVITY CONTROLLING MECHANISMS Nervous System Endocrine System Electrical messages Chemical messages Uses: Maintain homeostasis Maintain homeostas...

Endocrine System Endocrine System ACTIVITY CONTROLLING MECHANISMS Nervous System Endocrine System Electrical messages Chemical messages Uses: Maintain homeostasis Maintain homeostasis Response faster slower time: Duration of shorter longer response: What Excitable tissues Target cells cells/tissues -​ Muscles -​ Cells with receptors does it -​ glands x affect: Receptors: N/A Each cell has specific receptors These two systems work together. The Nervous system can even regulate activity of the Endocrine system. GLANDS Type Ducts? Produce: Other Info (Y/N) Exocrine yes Substances such as Related to digestion and tears, sweat, saliva, sweat glands breast milk, digestive juices, etc. Endocrine no hormones Highly vascularized Some glands, like the pancreas, have both endocrine and exocrine portions. NEUROENDOCRINE LINK There is a (weak/strong) connection between the nervous and endocrine systems. The major connection between the two is the hypothalamus, which is a major regulator of the endocrine system. CHEMICAL MESSENGERS Hormones o (short/long) distance chemical messengers. o Produced in one part of the body and have their effect (at the same part/somewhere else) part of the body. Autocrine o Secretion that is produced by a cell and affects the activity of that cell (self regulating). o Very localized effects. Paracrines o A local signaling molecule. o Secreted by a cell and affects neighboring cells. ▪ (Does/Doesn’t) affect activity of the cell which produced it. Pheromones o Chemicals that are produced by one organism and affect the activity of other organisms. o Usually used as an attractant or repellant HORMONE CLASSIFICATIONS (based on biochemical makeup) Amino acid based (non-steroid) o Derived from peptides/proteins. o Most of the hormones in our body. o They are water soluble, which makes them easy to transport in the blood, but they’re unable to pass across the plasma membrane. o Receptor for these must be on the outside of the cell. Steroid o Derived from cholesterol. o They are lipid/fat soluble, which makes them a little more difficult to transport in the bloodstream, but they can pass across the plasma membrane. o Receptors can be located inside the cell. o Produced by 2 structures: ▪ gonads ▪ Cortex of the adrenal gland Eicosanoid o Not considered a true hormone. ▪ Released by cell membranes, but only have localized effects. o They are bio active lipids. o Types: ▪ prostaglandins Have multiple effects in cells. ▪ leukotrienes Generally involved in inflammatory response or related to the immune system. HORMONE ACTIONS Target cells o Any cell that has a receptor for a hormone. o Hormone will change the permeability of its target cell once it binds to the receptor. ▪ The effect of this hormone is dependent on the target cell. ▪ The same hormone can have different effects, depending on what type of cell it is interacting with. o Potential effects: 1. Open or close ion channels Changing permeability of the cell. This leads to changes in membrane potential. 2. Stimulate protein synthesis Some hormones will directly activate DNA to produce new proteins. 3. Activate or deactivate enzymes Proteins that already exist could be turned on or off. 4. Promote secretion Hormones could stimulate exocytosis by the target cell. Target cells may produce a number of things that could cause local or global changes. One hormone can cause a target cell to release a different hormone. 5. Stimulate mitosis/division Cell division and growth (replication of cells). HORMONAL MECHANISMS Mechanism Receptor location Type of Involves Activation Amino Plasma membrane indirect G protein Acid-based Secondary messenger Steroid Inside nucleus direct N/A STEROID ACTION 1.​ Hormone secreted by an endocrine gland. 2.​ Travels through the bloodstream to a target cell. 3.​ Hormone diffuses through the plasma membrane of the target cell. 4.​ Binds with intracellular receptor. ○​ Receptor usually located in the nucleus. 5.​ Activated steroid/receptor complex acts as a primer and binds to a specific receptor protein on DNA. ○​ Different steroid hormones could activate different genes and cause different proteins to be produced. 6.​ Transcription initiated. 7.​ DNA translated. 8.​ proteins produced (could be enzymes, structural proteins, or export proteins). NON-STEROID ACTION Two mechanisms: 1.​ AMP mechanism 2.​ PIP-calcium mechanism ❖ CYCLIC AMP MECHANISM 1.​ Hormone secreted by an endocrine gland. 2.​ Travels through the bloodstream to a target cell. 3.​ Hormone binds to a specific membrane receptor on the outside surface of the cell. 4.​ Modified receptor binds with G protein. (which is an internal peripheral protein) 5.​ G protein is activated. 6.​ Activated G protein activates an enzyme called adenylate cyclase. 7.​ Adenylate cyclase generates cAMP from ATP. 8.​ cAMP stimulates another enzyme, called protein kinase, to react. 9.​ Protein kinases causes proteins to be phosphorylated (add phosphate to existing proteins) – this can either activate or deactivate them. 10.​Phosphodiesterase degrades cAMP and shuts the cycle off. ❖ PIP-CALCIUM MECHANISM 1. Hormones secreted by an endocrine gland. 2. Travels through the bloodstream to a target cell. 3. Hormone binds to membrane receptor. 4. Modified receptor binds with G protein. 5. G protein is activated. 6. Activated G protein activates phospholipase. 7. Phospholipase splits PIP2 into DAG and IP3. 8. DAG activates protein kinases (just like cAMP in other mechanism), which causes phosphorylation of existing proteins (activating or deactivating them).  9. IP3 triggers release of calcium from Endoplasmic Reticulum. 10. Calcium acts as an additional secondary messenger, catalyzing additional reactions in the body. FACTORS AFFECTING HORMONE ACTION Hormone level in bloodstream o The more in the bloodstream, the greater the activity. # of receptors in/on target cells o The more we have, the greater the activity. Receptor affinity o Some receptors have greater affinity for hormones than others. o The higher this is, the greater the activity. TYPES OF REGULATION Up Regulation o The effect of continued exposure to a hormone results in (more/fewer) receptors for that hormone, which means the cells will become (more/less) active. o If there was a stress that caused a hormone to be produced, the cells will respond by (increasing/decreasing) the response to get us back to homeostasis. o The effect of the hormone increases the number of receptors for that hormone. Down Regulation: o The continued release of a hormone results in a decrease in the number of receptors for that hormone. o Increase in level of hormone (lessens/increases) the effect of that hormone. HORMONE INTERACTIONS Permissiveness o This is where one hormone requires a second hormone in order to exert its fullest effects. o Ex. Thyroid hormone assisting reproductive function Synergism o Multiple hormones produce the same effects. o Combined effects are stronger. o Ex. glucagon and norepinephrine regulating blood glucose Antagonism o Sometimes hormones work in opposition to one another. o This helps set up feedback systems. o Ex. insulin and glucagon having opposite effects on blood sugar levels MODES OF ENDOCRINE GLAND STIMULATION Humoral o Changes in blood chemistry/concentration. Increase or decrease in ions or nutrients in the blood may be detected by the cell, and it will respond. Neural o Nervous stimulation can activate a gland to secrete a hormone. Hormonal o One endocrine gland is activated by a hormone produced by a different endocrine gland. o A “tropic” hormone is one whose target cell is another endocrine gland. All endocrine system activity has an override with the nervous system. The two systems work together. Endocrine gland stimulations are inhibited by negative feedback systems. ENDOCRINE GLANDS pituitary: an extension off of the brain. thyroid: surrounds the trachea. parathyroid: embedded within the thyroid. adrenals: on top of the kidneys pancreas: in the abdominal cavity gonads: testes in the male and ovaries in the female. pineal: in the brain. thymus: (is/is not) very active in adults. PITUITARY GLANDS (HYPOPHYSIS) Posterior pituitary (neurohypophysis) o Composed of neural tissue. o Outgrowth of the hypothalamus o Extends off of the infundibulum. o (does/does not) produce hormones. only stores and secretes them. Anterior pituitary (adenohypophysis) o Next to the posterior pituitary. o Composed of glandular tissue. ▪ (does/does not) produce secretions o An out-pocketing of the oral cavity (specifically an area called rathke's pouch). Infundibulum o Stalk extending off of the hypothalamus. o Anchors the pituitary gland. o Of neural origin. There is only a vascular connection between anterior and posterior parts of the pituitary. TROPIC HORMONES Their target tissues are other endocrine glands. Cause the production of another hormone. = HORMONES SECRETED BY POSTERIOR PITUITARY The posterior pituitary gland does not produce hormones; it only stores and secretes them. Both of these hormones are amino acid based and use the PIP calcium mechanism. 1.​ Oxytocin ○​ Stimulates smooth muscle contraction. ▪ Causes contract ▪ Also involved with milk ejection (not production) during nursing. ○​ Functions through positive feedback. ○​ also involved with sexual arousal & sexual satisfaction; known as “cuddle hormone” ○​ functions as an amnesiac, which means it helps individuals forget the past 2.​ Antidiuretic Hormone (ADH) ○​ Regulates water balance ▪ Targets the kidney tubules and causes them to reserve more water. Prevents urine formation. ▪ Helps in osmoregulation of our body. ▪ The hypothalamus monitors the solute concentration (tonicity) of the blood. It can activate secretion of ADH. ▪ Alcohol inhibits ADH. HORMONES SECRETED BY ANTERIOR PITUITARY These are produced by the anterior pituitary, but production is activated by a signal from the hypothalamus. All are amino acid based and use cAMP method. 1.​ growth hormone (GH) 2.​ thyroid stimulating hormone (TSH) 3.​ adrenocorticotropic hormone (ACTH) 4.​ Gonadotrophs ○​ FSH & LH 5.​ prolactin (PRL) 6.​ pro-opiomelanocortin (POMC) ~ not really considered a hormone yet ○​ Causes production of the body’s own opioids (related to pain suppression). ○​ Related to melanocytes, which produce melanin. ○​ The “cortin” portion means it is related to the adrenal cortex, and it has some effects with ACTH. Adenohypophyseal hormones and their effects 1.​ GROWTH HORMONES (GH) Actions: Stimulates cell growth and division, protein synthesis, fat metabolism, and glucose conservation. Most importantly involved with growth of muscles and bones. Disorders: pituitary dwarfism: o Deficiency of GH in children. o Overall small size. gigantism:shu o Excess GH in children. o Overall large size. acromegaly: o Normal levels of GH as a child, but increases as an adult. o Characteristic large faces, hands and feet. Cascade: 1.​ hypothalamus secretes GHRH (Growth Hormone Releasing Hormone). 2.​ GHRH affects somatotropic cells of anterior pituitary and they begin GH synthesis. 3.​ GH gets in the bloodstream and has both direct and indirect effects on target tissues. 4.​ Increased amount of circulating GH triggers production of GHIH (Growth Hormone Inhibiting Hormone, aka somatostatin). 5.​ GHIH shuts off production of GHRH in order to stop production of GH. Direct Actions: Increases blood levels of fatty acids o Takes fats from fat stores and puts them in the bloodstream. Stops glucose uptake and metabolism o Leave glucose in the bloodstream so that it can go to active cells. Encourages breakdown and release of glucose from glycogen in liver o Increases the amount of glucose that is available for energy. o Called diabetogenic effect- when we break down glycogen to release glucose. o GH is an anabolic (tissue building) hormone. Indirect Actions: Operates through IGFs (Insulin-like Growth Factors- also called somatomedins) o GH targets cells of the liver and causes the production of IGFs. o IGF’s then stimulate uptake of amino acids from blood into cellular proteins. ▪ protein synthesis o Stimulate uptake of sulfur into matrix of cartilage. 2. TSH Thyroid Stimulating Hormone is called thyrotropin. Stimulates the development and secretion of the thyroid gland. Cascade: 1.​ Hypothalamus secretes TRH (thyrotropin releasing hormone). 2.​ TRH causes thyrotrope cells of anterior pituitary to produce TSH. 3.​ TSH activates the thyroid gland. 4.​ Increased levels of TSH inhibit both the hypothalamus and thyrotrope. ○​ Shuts off TRH through negative feedback loop. o Also stimulates the production of somatostatin (which helps shut off GH so we get no more GHRH produced). 3. ACTH adrenocorticotropic Hormone Stimulates the adrenal cortex (outer portion of the gland) to release corticosteroid hormones. o Predominantly stimulates production of glucocorticoids. ▪ Involved in helping the body resist stress. Cascade: 1.​ Hypothalamus secretes CRH (Corticotropin Releasing Hormone). 2.​ CRH stimulates corticotrope cells to release ACTH. 3.​ ACTH stimulates adrenal cortex to release glucocorticoids. 4.​ Increased levels of glucocorticoids stop CRH. 5.​ ACTH secretion stops. Stressors that promote CRH release → fever, hypoglycemia 4. GONADOTROPINS Regulate functions of gonads. Both ovaries and testes produce two types, FSH (follicle stimulating hormone) and LH (luteinizing hormone). o FSH stimulates gamete production (eggs in females and sperm in males). o LH promotes production of gonadal hormone (ovaries release female sex hormones and testes release male sex hormones). ❖ MALE FSH stimulates sperm production. LH stimulates interstitial cells of the testes to produce testosterone. ▪ Testosterone gives males secondary sex characteristics. ❖ FEMALE FSH stimulates ova production. FSH and LH work together to cause maturation of eggs, which are kept in follicles in the ovaries.  LH triggers ovulation and promotes synthesis of ovarian hormones (estrogen and progesterone) which lead to female secondary sex characteristics. Cascade: 1.​ At puberty, the hypothalamus secretes GnRH (Gonadotropin Releasing Hormone). ○​ Almost none in the bloodstream before puberty. 2.​ GnRH stimulates gonadotrope cells of the anterior pituitary to secrete gonadotropins. 3.​ Gonadotropins cause gonads to mature and begin producing their own hormones. 4.​ Increased levels of gonad hormones suppress FSH and LH by suppressing GnRH. 5. PROLACTIN (PRL) Stimulates milk production by the mammary glands in the breasts. May enhance testosterone production in males. Cascade (Cycling): 1.​ High estrogen levels stimulate release of PRL from the hypothalamus. 2.​ PRH and estrogen stimulate lactotropes of anterior pituitary to secrete prolactin by suppressing PIH (Prolactin Inhibiting Hormone) production. 3.​ Prolactin production is brief due to ovarian hormone cycling. 4.​ Decreased estrogen stimulates production of PIH from hypothalamus. 5.​ Once PIH is produced, prolactin production stops. (not enough prolactin to actually produce milk) There are prolactin releasing factors (PRF), but their function is not completely understood Men have the inhibitor (PIH) and no estrogen to shut this off. Cascade (Pregnant): 1.​ High estrogen effects same (Shuts off PIH and prolactin is triggered) 2.​ prolactin triggered near end of pregnancy and prolactin/milk is being produced 3.​ suckling maintains PRL production.  ○​ Woman will continue to produce milk as long as she continues to breastfeed 4.​ Lack of suckling and return of normal hormonal cycles brings about PIH production, and lack of prolactin will cause the end of milk production. Identify the hormone producing organs, list the hormones each produces, and discuss the actions of each product. Describe the histological composition of each of the endocrine glands to illustrate how the hormones are produced. Outline the feedback mechanisms that control endocrine gland activity. THYROID GLAND 2 lobes connected by isthmus. largest pure endocrine gland in the body. Located below the larynx and around the trachea. Histological Composition: Gland composed of follicles made up of epithelial cells. o Called follicular cells. Follicular cells produce thyroglobulin, which is a protein that will become an amino acid based hormone. o act like steroid hormone (need protein carrier w/ receptor on inside of cell) Unique because it both stores & secretes. o thyroglobulin, which is a precursor for thyroid hormone, is stored within the follicle as colloid. o Thyroid hormone is derived from colloid. ▪ thyroglobulin + iodine = thyroid hormone (TH) Also contain parafollicular cells (located within the follicle), which produce calcitonin. o Calcitonin is not stored; it is immediately secreted.  Thyroid Hormone (TH or Thyroxine) Description Consists of iodine, which comes from your diet, and thyroglobulin. Actually 2 separate hormones: ​ T3 = Thyroglobulin + 3 iodine’s ▪ Action: how active cells are in taking up thyroid hormone ​ T4 = Thyroglobulin + 4 iodine’s ▪ Action: circulates in blood stream & converts to T3 ▪ cells prefer T4 over T3 Almost all cells in the body have receptors for thyroid hormone, except: thyroid, brain, spleen, testes, uterus Main hormone that regulates metabolic activity. Functions Increases basal metabolic rate and heat production. ​ Main metabolic function: Oxidation of glucose to produce ATP. ​ calorigenic effect = the production of heat from breakdown of glucose. Maintains blood pressure. ​ Causes production of additional adrenergic receptors – these are on the surface of blood vessels and causes vasoconstriction. Regulates tissue growth and development. ​ Especially skeletal and muscular tissue. Maturation of reproductive organs.  Hormone-Producing Structures Identify the hormone producing organs, list the hormones each produces, and discuss the actions of each product. Describe the histological composition of each of the endocrine glands to illustrate how the hormones are produced. Outline the feedback mechanisms that control endocrine gland activity. ADRENAL GLANDS ​ Paired glands located on top of each kidney. ​ Composed of a cortex (outer) and a medulla (inner): o The cortex is derived from glandular epithelium o The medulla is derived from simplified neural (endings) tissue. ​ Produces hormones that help us deal with stress. (Emotional or physical stress) Cortex Hormones: ​ Produces three classes of corticosteroids: 1. ​ Mineralocorticoids – most superficial, salt 2. ​ Glucocorticoids – sugar 3. ​ Gonadocorticoids – deepest layer, sex *salt, sugar, sex, the deeper you go, the better it gets Histological Composition of the Cortex: ​ Three different regions or “zonas”: 1. ​ Zona glomerulosa – produces mineralocorticoids 2. ​ Zona fasciculata – produces glucocorticoids 3. ​ Zona reticularis – produces gonadocorticoids Discuss four mechanisms of mineralocorticoid secretion. ​ Mineralocorticoids Description ​ Aldosterone is the major hormone which accounts for 90% of mineralocorticoids. ​ Regulate the electrolyte concentration of extracellular fluids ​ The most important electrolytes are sodium and potassium (mainly sodium). ​ Helps to regulate osmotic (water) balance Actions ​ Stimulates sodium reabsorption in the kidneys ​ In distal parts of kidney tubules ​ Sodium can then make an osmotic gradient, which affects the movement of water and other ions. ​ Exerts an effect on blood pressure and volume ​ If sodium moves into the bloodstream, water follows, which adds more volume to the blood vessels and results in increased pressure against the vessel walls. Feedback ​ Humoral triggers cause an increase in aldosterone. ​ Secretion stimulated by: ​ High potassium level in the blood. ​ Low sodium level in the blood. ​ Low blood volume ​ Low blood pressure  Aldosterone ​ Renin-angiotensin mechanism: Most important mechanism of Secretion aldosterone production. Mechanisms ​ The liver is constantly producing lots of proteins. One called angiotensinogen is an inactive protein. ​ Under the proper stimuli (low BP), the kidneys start to produce renin ​ Renin converts angiotensinogen to an active form called angiotensin 2 ​ Angiotensin 2 activates Zona glomerulosa of the adrenal cortex to produce aldosterone ​ Aldosterone causes sodium reabsorption. ​ Plasma Concentration Mechanism ​ Controlled by solute concentrations in the blood. ​ When sodium levels are low, aldosterone is produced by Zona glomerulosa ​ ACTH Mechanism ​ Stress causes the hypothalamus to produce CRH, which causes the anterior pituitary to produce ACTH, which causes the adrenal cortex to become active. ​ Can cause mineralocorticoid production. (Usually not a lot) ​ Atrial Natriuretic Peptide (ANP) ​ Pressure on the walls of the heart due to high blood pressure stimulates the heart to release ANP. ​ ANP shuts off the production of renin ​ Decreases blood pressure.s *Low blood pressure stimulates renin-angiotensin mechanism and high blood pressure stimulates ANP mechanism*  Glucocorticoids Description Major hormone is Cortisol. ​ Main function is to regulate energy metabolism in response to stress Actions ​ Maintain blood sugar levels. ​ Cortisol stimulates a process called gluconeogenesis, which is the production of new carbohydrates (glucose) from protein or fat, which are non-carbohydrate substances. ​ Maintain blood volume by preventing uptake of water from the bloodstream by cells. Feedback ​ CRH (corticotropin releasing hormone) released by hypothalamus promotes release of ACTH, which activates the adrenal cortex to produce cortisol. ​ Increased cortisol inhibits CRH release by the hypothalamus. Effects of Stress: ​ Increases cortisol → o Increases gluconeogenesis o Liberates fatty acids for energy (taking them out of storage). o Breaks down proteins into amino acids. o Assist in vasoconstriction. · ​ Keyways to tell if someone is stressed vasoconstriction causes high blood pressure  Gonadocorticoids Description ​ Produces weak androgens. ​ Most prevalent is DHEA, which is the precursor that gives rise to hormones like estrogen and testosterone ​ Ultimately produces sex hormones. ​ Gonadocorticoids help to time puberty. ​ DHEA helps provide sex drive to women. (Testosterone in particular) Feedback ​ Increased ACTH stimulates production of the gonadocorticoids ​ Doesn’t appear to be a shut off mechanism in place. Medulla Hormones: ​ Epinephrine ​ Norepinephrine Histological Composition: ​ The tissue that makes up the adrenal medulla has chromaffin cells ​ Chromaffin cells produce epinephrine and norepinephrine which are released into the bloodstream. (Combination = adrenaline )  Epinephrine & Norepinephrine stop here Actions ​ Stress promotes release of epinephrine and norepinephrine by stimulating the sympathetic nervous system. ​ Blood sugar levels rise ​ Blood vessels constrict ​ Heart rate increases ​ Blood pressure rises ​ Blood is diverted to the brain, heart, skeletal muscles, and preganglionic sympathetic nerve endings in adrenal medulla (organs that are important in fight or flight). PANCREAS ​ Located in the abdominal cavity behind the stomach. Connected to the small intestine. ​ Has both exocrine and endocrine components: o Exocrine portion: secretes substances into a duct; used in digestion o Endocrine portion: some of the tissue of the pancreas secretes hormones that go directly into the bloodstream Histological Composition: ​ Acinar cells o The exocrine portion (digestive enzymes). ​ Pancreatic islets (Islets of Langerhans) o Alpha cells – produce glucagon o Beta cells – produce insulin *Antagonistic interaction because they work against each other (opposite) ​  Glucagon Actions ​ Increases blood sugar levels. ​ Functions on the liver to release glucose into the bloodstream. ​ Breakdown of glycogen into glucose ​ Synthesizes glucose from lactic acid and non-carbohydrate molecules. Feedback ​ Low blood glucose has a humoral effect on the pancreas and causes it to release glucagon ​ Sympathetic nervous stimulation promotes release. ​ Somatostatin (GHIH) inhibits release of glucagon. Insulin Actions ​ Lowers blood sugar levels. ​ Influences protein and fat metabolism. ​ Enhances uptake of glucose into cells. ​ Inhibits breakdown of glycogen into glucose ​ Inhibits the conversion of amino acids or fats to glucose. ​ Promotes the oxidation of glucose for ATP production. ​ Promotes the production of fat/lipid Feedback ​ High blood glucose has a humoral effect on the pancreas and stimulates beta cells to produce insulin. ​ Parasympathetic nervous stimulation causes release. ​ Hormonal influences also stimulate beta cells to produce insulin.  Sex Hormones (Testosterone, Estrogen, & Progesterone) Actions ​ Testosterone ​ Development and maintenance of male reproductive organs. ​ Secondary sex characteristics (increased muscle mass, hair, oily skin, deeper voice). ​ Increases sex drive ​ Important in sperm (male gamete) production. ​ Estrogen ​ Maturation and maintenance of female reproductive organs. ​ Secondary sex characteristics (absence of male characteristics, lack of oil, reduced muscle mass, no enlargement of vocal cords, redistribution of fat in certain areas of the body). ​ Progesterone ​ Functions with estrogen to: ▪ ​ Promote breast development. ▪ ​ Cause cyclic changes in uterine lining - regulate the menstrual cycle. Feedback ​ Regulated by gonadotropins (FSH and LH from pituitary gland). GONADS ​ Testes → testosterone ​ Ovaries → Estrogen & Progesterone The gonads produce the same sex hormones as the zona reticularis (this was supplemental production). ​  Melatonin PINEAL GLAND ​ Extends from the roof of the third ventricle in the diencephalon Histological Composition: ​ Made up of cells called pinealocytes o Produce a hormone called melatonin Actions ​ Promotes drowsiness ​ Inhibits sexual maturation ​ Therefore, helps time onset of puberty ​ Activity of the pinealocytes is suppressed when the sun is out, but active when the sun is gone. THYMUS ​ Beneath the sternum in the thoracic cavity. ​ Size diminishes with age. o Activity decreases later in life. o Most function in the immune system. Hormones of the Thymus: 1.​ Thymoproteins 2.​ Thymic factor 3.​ Thymosins ​ All function in immunity. ​ Influence development of special white blood cells called t-lymphocytes. o Part of our immune system that goes out and targets/recognizes specific pathogens and attacks them. ​ Most active when we’re young, so we have a stronger immunity when we’re young.  OTHER HORMONE PRODUCERS Structure: Produces: Actions/Example/Other Info: Heart ANP ​ Inhibits aldosterone and changes composition of urine by acting on the kidneys GI Tract Digestion hormones xample: hormones that keep intestines moving (many different) Ghrelin – hungry tomach growling) Placenta Estrogen ​ Exists only in a woman’s body during pregnancy. ​ Allows for exchange between mom and baby. Progesterone ​ Starts to develop after fertilization has occurred. ​ Takes over for the ovaries and keeps the uterus hCG (human nutrient rich and vascularized horionic ​ Helps cause production of capillary bed to allow gonadotropin) for exchange with the mother. ​ These all help regulate the development of the embryo Kidneys Erythropoietin ​ Stimulates the kidneys/bone marrow to produce red blood cells Skin ​ The inactive form of vitamin D Cholecalciferol ​ Activated in the liver ​ Helps us absorb calcium in our intestines Adipose Tissue Leptin ​ As we store more and more lipids (fats) in this tissue, it produces leptin ​ Acts on the amygdala to reduce our appetite. ​ It also increases energy expenditure. ENDOCRINE GLAND DEVELOPMENT ​ Arise from all three embryonic germ layers. o The glands that produce steroid hormones (gonads & adrenal cortex) come from the mesoderm. o Amino acid hormone secreting structures comes from endoderm and ectoderm. ​ Aging changes the rate of hormone production. o Women stop cycling and go through menopause. o Testosterone levels decrease in males. o Puberty is due to hormone level. ​ Hormone production can be affected by environmental cues. o Stimuli from the environment can create stressors which affect the adrenal gland. o Sun can affect vitamin D and calcium levels. *Thymus also changes a lot in our body gets smaller and smaller as we get older Reproductive System Worksheet ❖ MALE ANATOMY Main Structures: x Testes (gonads) sperm producing structures Accessory Structures: Scrotum - sac like holds testes outside the abdominal cavity Epididymis- storage warehouse of the sperm. Passageway Ductus deferens - sperm goes through here first Ejaculatory duct - then goes through this. This merges to form the urethra Urethra- is the length of the penis Penis - organ of copulation Accessory glands Seminal vesicles Prostate gland: one of these, increase in size as men age Bulbourethral gland: aka cowper's gland TESTES TUBULES Description/Function Lobules: -​ division/sections of the testes Seminiferous -​ Tubular system that makes up the testes (highly branched) Tubules: -​ Site of sperm production aka “assembly line” loop Tubulus rectus: -​ Continuous w/ seminiferous tubules -​ Straight tubule between seminiferous and rete Rete testis: -​ Continuous with tubulus rectus, central hub where all tubules connect Efferent ductules: -​ Carry sperm to epididymis from rete testis -​ “exit” Epididymis: -​ Sperm storage HISTOLOGICAL COMPOSITION Seminiferous tubules o Site of sperm/gamete production. Interstitial cells (of Leydig) o Cells located between the seminiferous tubules. o Produce testosterone (sex hormone also known as androgens. ▪ Increased testosterone helps stimulate sperm production. TESTICULAR BLOOD FLOW Blood supplied by testicular arteries, and drained by testicular veins. The blood delivered to the testes is (cooler/warmer) than the blood delivered to the rest of the body because it passed through the pampiniform plexus. o Arterial blood delivered from the abdominal cavity going (toward/away from) the testes is (cool/warm). o Venous blood going (toward/away from) from the testes is (cooler/warmer). o As the arterial and venous blood pass each other, the heat from the arterial blood gets dissipated into the cooler venous blood & the arterial blood is cooled before it reaches the scrotum. SCROTUM sac-like structure outside of the male’s body. Consists of skin and superficial fascia. Includes a right and left side to separate testes into compartments. Has muscles that allow maintenance of optimal temperature. o Muscles contract (when cold) and relax (when warm), changing how close the testes are to the body. o These muscles include: ▪ dartos ▪ cremaster o Helps maintain a temperature (lower/higher) than that of the body. (specifically 3°C (above/below) body temperature). PENIS Humans use a process of internal fertilization (sperm and egg unite inside the body). The penis is a specialized copulatory organ which delivers sperm to the female reproductive tract. o Aims urine as well as ejaculatory fluids. The penis is divided into three regions: root, shaft, & glans (aka head). o The glans penis is covered with extra tissue called the prepuce (aka “foreskin”). o In some cultures, this tissue is surgically removed in a procedure called circumcision. These glands collectively produce semen. (But not at the same time!) o bulbourethral gland(s) are activated before the others & this mucus is secreted before ejaculation (often called pre-ejaculatory fluid). ERECTILE TISSUE Erection: change in size and rigidity. Tissue Types: corpora cavernosa o Two larger bodies of erectile tissue. corpus spongiosum o Single smaller body at the bottom which surrounds the urethra. o When it is filled with blood, it keeps the urethra open so that sperm can pass through. Both types are a spongy network of connective tissue, smooth muscle and vascular space. Upon sexual excitement, the arteries that supply the penis dilate and fill this cavernous tissue with blood and that causes the penis to become larger and firmer. o Collapses the veins that drain the penis and traps the blood.  MALE REPRODUCTIVE PHYSIOLOGY Erection Phase (Parasympathetic = point) Stimulus is usually visual for men and tactile/touch for women. Sexual arousal is a positive feedback system. Steps: 1. Sexual arousal causes parasympathetic nervous fibers to release nitric acid (NO) at the base of the penis. 2. Nitric acid causes dilation of arterioles at the base of the penis. 3. erectile bodies (corpus spongiosum & corpora cavernosa) fill with blood, enlarging the penis. 4. Corpora cavernosa expands, compressing drainage veins (blood is trapped). 5. bulbourethral glands also stimulated by parasympathetic reflex upon arousal. Ejaculation Phase (Sympathetic = shoot) 1. Continued stimulation causes the sympathetic nervous system to send a signal. 2. Causes (voluntary/involuntary) smooth muscle contractions to push contents into the urethra. (sperm pushed through duct system & glands produce fluid). 3. Also close off the pathways to the bladder by constricting sphincter. 4. semen is expelled out the end of the penis through rapid series of contractions. (Ejaculation & orgasm occur) Males have to go through a refractory period.  SPERMATOGENESIS (production of spermatids) Process of sperm production in the seminiferous tubules. male start to produce sperm at puberty and continue until death. o Produce on average spe million sperm per day. (Where are they stored? epididymis) Process begins at basal lamina and products are released into lumen. Spermatogenesis Process 1. A single diploid spermatogonia cell undergoes mitosis when stimulated to divide and produces type A and B daughter cells. o Daughter cells are genetically (unique/identical) to each other and the parent cell. 2. Type A cells stay at basal lamina and replace the original spermatogonia that divided by developing into a spermatogonia and continuing to replace over and over. Type B cells are called primary spermatocytes. o Type A cell are (haploid/diploid). o Type B cells are (haploid/diploid). 3. Primary spermatocytes undergo meiosis 1 to produce two secondary spermatocytes. o Secondary spermatocytes are (diploid/haploid) and genetically (unique/identical) to each other and the parent cell. 4. Each secondary spermatocyte undergoes meiosis 2 to become two spermatids (4 total spermatids are produced). o Spermatids are (diploid/haploid) and are genetically (unique/identical) to each other and the parent cell. Spermatids (are/are not) capable of fertilization. Sperm are produced up until a male dies. Around 400 million sperm are produced per day  SPERMIOGENESIS (modification of spermatids to become spermatozoa) Spermiogenesis Process 1. Spermatid decreases cytoplasmic volume and forms a tail (called a flagellum). o Loses organelles in the process. 2. Finished product known as a spermatozooan, which is an immature sperm. o Doesn’t gain ability to swim until in the epididymis but doesn’t really start swimming until in female reproductive tract; also not capable of fertilization until certain changes occur when in the female body. The process of going from a primary spermatocyte to an immature sperm takes approximately 64-72 days. Spermatozoan Parts Description Head -​ Contains male genetic material in haploid state -​ Male pronucleus Acrosome -​ Contains enzymes needed for fertilization -​ Thins in female reproductive tract Midpiece -​ Packed with mitochondria -​ Makes ATP with prostate gland secretion Tail -​ Flagella -​ Allows sperm to swim SUSTENTACULAR CELLS (“sertoli” OR “nurse” CELLS) These cells are needed because haploid sperm appear foreign to the body, so the immune system tries to kill them. Actions: Protect developing spermatocytes from the male’s immune system o blood-testis barrier in the male’s reproductive tract. ▪ Blood that is delivered to the testes has to pass through the sustentacular cells. e nourish dividing cells o Have some secretions that help to make the cells divide. Helps move the cells to lumen o So they can be transported to epididymis. Secrete testicular fluid o Functions as a transport medium in the lumen. o Fills lumen of seminiferous tubules to help get the spermatids to the epididymis. Dispose of eliminated cytoplasm o As spermatid is modifying. Regulate spermatogenesis  HORMONAL REGULATION Hypothalamus releases GnRH. GnRH stimulates the gonadotropin cells of the (anterior/posterior) pituitary to release gonadotropin. ○ Gonadotropins include: FSH and LH. ROLE OF FSH FSH stimulates sertoli cells to release androgen-binding protein (ABP). ABP attaches to outside of spermatogonia & causes them to accumulate testosterone. ○ Does this by causing receptors for testosterone to be produced. ROLE OF LH Need both LH and FSH for sperm/gamete production. LH causes interstitial cells in the seminiferous tubules to secrete testosterone. ○ Also a very small amount of estrogen. ROLE OF TESTOSTERONE Stimulates spermatogenesis o Through the binding of testosterone to ABP. Inhibits GnRH o As testosterone levels increase, this shuts off GnRH which then inhibits gonadotropins (FSH and LH) release. Has anabolic effects on accessory reproductive organs o Develops and maintains them. Promotes male secondary sex characteristics o denser bones, increased muscle mass, hair production, oily skin, and deeper voice. Boosts BMR o basal metabolic rate (BMR) – younger men can eat a lot and not gain much weight. o When adolescence starts to wane, they typically can’t do this anymore. Influence behavior o Increases sex drive, and also increases aggression. ROLE OF INHIBIN Produced by the sustentacular cells (aka Sertoli) cells when sperm count is (high/low). Inhibits release of FSH by inhibiting GnRH. o Shuts off production of ABP and stops sperm production.  Female Reproductive System Part Description/Function Ovaries -​ Site of gamete (ova/egg) production (gonads) -​ There are 2 (L/R) Oviducts -​ Tubules not continuous with ovaries (can cause problems, (Fallopian Tubes) indirect connections) (2) -​ Extends from ovary to uterus -​ Transport channel -​ Contains infundibulum, ampulla, isthmus Uterus -​ Upside down, pear shaped, muscular organs (single) -​ Thick walled muscular organ that receives, retains, and nourishes the ovum Vagina -​ External pathway -​ Birth canal External genitalia -​ Stuff you can see from the outside of the body with the naked eye -​ Contains mons pubis, labias majora and minora, greater vestibular glands, clitoris, and perineum Mammary glands -​ Not exactly a reproductive structure -​ Nutrient producing structure after baby is born -​ Linked to hormones -​ Milk producing OVARIES Gametes formed in the ovarian cortex before birth. o Gamete gets surrounded by protective cells and exist as ovarian follicles. o These cells are follicular or granulosar. ▪ follicular cells: first layer surrounding oocyte All follicles have this ▪ Granulosar cells: subsequent cell layers above follicular  OVARIAN FOLLICLES Follicle Description/Function Type Primordial Oocyte surrounded by a single layer of follicular cells. Women are born with all of the primordial follicles they will ever roduce. (Some/All) of these will start to ripen and become primary follicles with proper hormonal stimulation. Primary 2 layers of cells around it. Typically, just 4 or 5 primordial follicles will continue to develop to primary follicles. Secondary Key characteristic is the development of a fluid-filled cavity called an antrum. Generally, only 1 -2 secondary follicle(s) continues to mature and become a graafian follicle. Graafian Much larger in size. Oocyte is pushed away from edge and sits up on a stalk. Appears like a blister on the surface of the ovary. Ruptures to release oocyte in a process called ovulation. Fills with blood to become corpus hemorrhagicum. Corpus A glandular structure which secretes hormones that get the uterus Luteum ready for fertilization/pregnancy. If fertilization DOES occur, the corpus luteum will be maintained for about 3 months, and after this the placenta will take over and luteum will degenerate. If fertilization does NOT occur, the corpus luteum degenerates after about 14 days. Corpus Whether or not fertilization occurs, corpus luteum become corpus Albicans Albicans. This is basically just a scar on the ovary. OVIDUCTS: fallopian tubes- transport channel Ovulated oocyte released from the ovary into the peritoneal cavity. Ciliated fimbriae sweep oocyte into the oviduct. Oocyte travels first into the infundibulum, then into the ampulla, and lastly into the isthmus before reaching the uterus. The infundibulum, which is the closest part of the oviduct to the ovary, has cilia (finger-like projections) which are stimulated to pulse and create a wave/current to pull the egg into the oviduct. The ampulla of the oviduct is the normal site of fertilization. ectopic Pregnancy: when a fertilized egg tries to implant in the wall of the oviduct, on the outside of the uterus, on an abdominal organ, etc.; this is usually life-threatening to mother and baby. UTERUS Thick-walled muscular organ that receives, retains, and nourishes the fertilized ovum, This muscle is smooth and (involuntary/voluntary). Uterus Part Description Body -​ Major portion of the uterus -​ Underneath where fallopian tubes connect, where baby mostly implants Fundus -​ Arching part of the uterus above where the oviducts attach -​ Rounded, muscular top of uterus between oviducts Cervix -​ Very tiny canal -os -​ Constricted “neck” w/a cervical canal Internal os -​ Internal opening of the cervical canal closest to the uterus External os -​ External opening of the cervical canal furthest from the uterus -​ Typically plugged with a thick mucus -​ Prevents sperm and other things from getting through -​ Thins during ovulation Cervical canal is usually the width of human hair, but during birthing will dilate to 10 cm. A cervical plug made of mucous develops during pregnancy to prevent foreign pathogens/objects from reaching the baby. UTERINE WALL LAYERS perimetrium- outer layer myometrium - muscular layer o Composed of (voluntary/involuntary) smooth muscle. endometrium - inner lining o Highly vascular glandular portion. ENDOMETRIUM STRATA Stratum functionalis o Innermost layer of the endometrium. o Built up and then sloughed off if fertilization (does/doesn’t) occur. Stratum basalis o Portion of endometrium closest to the muscle. o Causes a thickening and vascularization of the stratum functionalis. ▪ Hormones cause it to rebuild the endometrium when it is sloughed off. VAGINA Female organ of copulation o Receptive organ for sperm birth canal o Baby passes through acidic environment o Prevents bacterial formation hymen o Very thin layer of tissue that “covers” the opening of the vagina  EXTERNAL GENITALIA (VULVA) Part Description Mons pubis Pad of fatty tissue on top of the pelvis. Prevents friction/pressure on the pubic symphysis during intercourse. Has lots of hair follicles associated with it. Labia majora (Inner/Outer) folds. (Does/Doesn’t) have hair follicles associated with it. Labia minora (Inner/Outer) folds. (Does/Doesn’t) have hair follicles associated with it. Greater Associated with walls of vagina and labia minora. vestibular Female counterpart to the male bulbourethral glands. glands Upon sexual arousal, nervous impulses stimulate production of musucs like fluid to aid insertion of the penis. Clitoris A collection of spongy epithelial tissue (erectile tissue) which fills with blood upon sexual arousal. Contains lots of nerve endings. Perineum Tissue that exists between the vulva and anus. Often tears during labor.  MAMMARY GLANDS modified sweat glands Both males and females have these. o Only functional in females due to hormonal regulation. Produce milk to nourish newborn. Part Description Part Description Lobes -​ Compartments Lactiferous -​ Behind nipple contains lobules sinus -​ Milk collects here & is stored Lobules -​ Smaller Nipple -​ Attachment point for compartments w/in breastfeeding each lobe containing glands Alveoli -​ Sacks at the end of the Areola -​ Toughened lobules that produce pigmented tissue milk surrounding the nipple Lactiferous -​ Milk travels through ducts these to nipple -​ Carries milk from alveoli to nipple  OOGENESIS (PRE-PUBERTY) In females, the process of gamete production starts before birth. It then stops and then doesn’t start up again until puberty. Oogenesis (Pre-Puberty) Process **All of this happens before birth** 1. Diploid oogonia undergo mitosis to produce two primary oocytes. o Primary oocytes are (haploid/diploid) and genetically (identical/unique) to each other and the parent cell. o These primary oocytes incorporate follicular cells to become primordial follicles 2. Primary oocytes start, but do not complete, meiosis 1. o Get arrested at prophase 1. At birth, there are~2 million primordial follicles in ovaries -- at puberty, just ~400,000 are left. OOGENESIS (POST-PUBERTY) Oogenesis (Post-Puberty) Process **All of this happens after birth, starting at puberty** 1. At puberty, some of those cells that are arrested in prophase 1 will complete Meiosis I and produce the first polar body and a secondary oocyte. o The secondary oocyte will go on to become a gamete/egg. o The polar cell is simply a supportive cell that will nourish and protect the embryo. o Both the secondary oocyte and polar body are (haploid/diploid). 2. First polar body undergoes meiosis 2 and produces 1 additional polar bodies. One secondary oocyte begins Meiosis II, but arrests at metaphase 2. 3. Secondary oocyte is ovulated (while still stuck in Meiosis II), and the process won’t finish unless fertilization occurs. Define fertilization, and indicate the time period in which it’s possible. OOGENESIS (POST-OVULATION) Ovum = fertilized egg ((haploid/diploid) technically). If fertilization does occur… Secondary oocyte completes meiosis 2. Produces one ovum and another polar body. Secondary oocyte is (haploid/diploid), and then becomes (haploid/diploid) as soon as the sperm combines with it. **Total produced by original diploid oogonia → 3 polar bodies & 1 ovum If fertilization does NOT occur… Secondary oocyte degenerates and never finishes its division (never completes meiosis 2). Phase Description Follicular Phase Includes everything prior to ovulation. In an “average/normal” 28-day cycle, this would be 14 days long. Steps: 1. primordial follicles become primary follicles. ○​ How many become primary? 4-5 ○​ Only one will dominate 2. primary follicles become secondary follicles. ○​ Only the one dominate does this o Theca folliculi forms ▪ Layer of connective tissue along the outer boundary of the follicle. ▪ The dark line of cells that appear different from the rest. o theca and granulosa cells are secretory & produce estrogens (as follicles are forming, the estrogen level in a woman’s body is increasing). o Zona pellucida is the glycoprotein-rich outer membrane. ▪ A transparent membrane surrounding the oocyte. ▪ This is what the enzyme in the acrosome of the sperm has to get through to reach the egg. o antrum begins to develop in the secondary follicle, and continues to develop & increase in size. 3. the secondary follicle becomes graafian follicle (aka vesicular follicle). o Corona radiata forms. This is a stock that forms and pushes the egg up from the wall (contains a secondary oocyte). Differentiating Cell vs. Follicle A secondary follicle contains a primary oocyte at first, which develops into a secondary oocyte. (change of oocyte type occurs within the secondary follicle) A Graafian follicle always contains a secondary oocyte. Ovulation Typically, only 1 secondary oocyte(s) is ovulated. (The number that are released increases with age – you’re more likely to have twins in your 30’s than in 20’s). What other factor affects this? genetics. During ovulation, women often experience: o pain o higher body temp o higher sex drive Steps: 1. The ovary wall ruptures and expels a secondary oocyte into the peritoneal cavity. (Secondary oocyte must then make its way into a fallopian tube.) Phase Description Luteal Includes everything after ovulation. Phase This phase is always 14 days long. Steps: 1.​ What was the graafian follicle fills with blood and the corpus hemorrhagicum forms. 2.​ The blood in the corpus hemorrhagicum is resorbed, but theca and granulosar- cells (secretory cells) produce the corpus luteum. 3.​ Corpus luteum secretes progesterone and estrogen. o progesterone is the more important of these. o If fertilization occurs, the luteum stays active for about 3 months and secretion continues until the placenta forms. o If fertilization doesn’t occur, the corpus luteum will degenerate after about 10 days to become corpus albicans (scar on ovary).  HORMONAL REGULATION Prior to The ovaries are producing estrogen. Puberty o This estrogen is an inhibitor of GnRH. o (posterior/anterior) pituitary isn’t releasing any gonadotropins and nothing is being stimulated in the ovary The sensitivity of the hypothalamus to estrogen changes around puberty (pineal gland secretions cause this). At Puberty Now estrogen no longer suppresses GnRH. The hypothalamus starts to secrete GnRH in rhythmic pulses ~ not continuous. As GnRH accumulates, it promotes FSH and LH production by the anterior pituitary. This initiates the process of the ovarian cycle. Fluctuations are normal – there is no real stable hormonal secretion in a woman’s body at first. It can sometimes take up to about 3 years for cycles to start to show some regularity. o menarche: first menstrual cycle which indicates that the hormonal cycling is starting to become stable/regular ▪ In some cases it never will – due to irregular patterns  Hormone Role FSH FSH stimulates the follicle cells to cause growth and maturation of the follicle. LH (Early Cycle) Causes the thecal cells to produce androgens (sex hormones). o Androgens converted to estrogen by granulosa cells. o Causes production of estrogen by the follicle. o As estrogen level increases, it inhibits release of FSH and LH. **because of change in sensitivity, it now takes (more/less) estrogen to shut off gonadotropin release ESTROGEN Shuts off release (not production) of FSH and LH. Stimulates follicle development. o Therefore, further increases estrogen production. Eventually, estrogen levels get so high, that it causes a burst of LH. o Called “LH surge”. NON-CYCLIC Has anabolic effects on female reproductive tract. ROLE OF o maturation and development of female sex organs. ESTROGEN Support short-term growth spurt of girls at puberty. Promotes female secondary sex characteristics. LH (Mid Cycle) Surge of LH stimulates meiosis 1 to complete in the dominant primary follicle. o Complete Meiosis I to produce a secondary oocyte. Stimulates ovulation. All this LH inhibits estrogen production. o Lack of estrogen causes follicles to no longer develop. Transforms ruptured follicle into corpus luteum. o Then corpus luteum starts to produce progesterone and estrogen. ▪ Mostly progesterone. o Corpus luteum also produces inhibin, thus shutting off FSH and LH. PROGESTERONE ​ Inhibits FSH and LH, which shuts off follicle development. INHIBIN Inhibit FSH and LH, which shuts off follicle development.  *** If fertilization doesn’t occur, corpus luteum degenerates and stops producing estrogen and progesterone. Now there are no hormones to suppress FSH and LH, and the cycle starts back up. UTERINE CYCLE (Menstrual Cycle) Associated with hormonal changes in the endometrial lining of the uterus due to hormonal regulation. Phase Description Menstrual (Begin/Ends) the cycle. Days 1-5 Ovarian hormones are at (lowest/highest) level. FSH and LH have not been initiated yet. Corpus luteum has been absorbed. Absence of hormones stimulates sloughing off of uterine lining. Functional layer of endometrium detaches and menstruation occurs. By day 5 of the menstrual phase, the follicles are producing estrogen, which pushes us into the proliferative phase. Proliferative Estrogen causes endometrium to regenerate. Days 6-14 Progesterone receptors develop in endometrial cells. Ends with ovulation (surge of LH puts stop to build up of functional layer). Secretory After ovulation, corpus luteum has started to produce progesterone. Days 15-28 Causes the endometrial layer to become more vascularized, readying it for implantation in case the fertilized ovum gets there. Progesterone causes accumulation of mucus in the cervical canal (creates cervical plug). Continues as long as progesterone is present. When levels start to decline, initiates breakdown of the endometrial functional layer. end of cycle. (Hormone levels decline & cycles starts over) FEMALE SEXUAL RESPONSE Arousal similar to male. o blood engorgement ▪ Mainly of the clitoris, which is composed of cavernous tissue. ▪ Also erectile tissue breast and wall of vagina. o Stimulates vestibular gland activity ▪ Produce lubricating mucus. Orgasm does not include ejaculation or refractory period. o sympathetic nervous impulses cause contraction of smooth muscle. ▪ Increase in muscle contraction, pulse, and blood pressure. ▪ Feeling of pleasure and relaxation. o This can be repeated without a refractory period. HUMAN SEXUAL DEVELOPMENT We all start out female. Gender is determined by genetic composition of sperm because the father is a heterozygote. o Women: XX o Men: XY SRY gene on the Y chromosome promotes the development of testes. Embryo is sexually indifferent until approximately 2 months post-conception. o Gonadal development begins at about week 5. SEXUAL DIFFERENTIATION Gonadal ridges begin formation about 5 weeks post conception. Two sets of ducts, mullerian and wolffian, form. (only one will be maintained!) o mullerian: maintained by female o wolffian: maintained by male primordial germ cells are deposited. Genital tubercle develops into external genitalia. o Contains: ▪ Urethral groove: center ▪ Urethral folds: sides of groove ▪ Labioscrotal swellings (pouches):around the folds  Male Sexual 1. seminiferous tubules form in gonadal ridges and link Differentiation together with the wolffian ducts. o (Directly/Indirectly) connect. 2. Developing testes secrete AMH (anti-mullerian hormone) which causes mullerian ducts to degenerate. 3. Genital tubercle enlarges to form penis. 4. Urethral folds fuse together to form urethra. 5. Labioscrotal folds fuse to form the scrotum. 6. testosterone production guides secondary sexual development. o Cause penis & testes to continue to develop. 7. Testes ultimately descend into scrotum approximately 2 months before birth. o Very high in the abdominal cavity before. Female Sexual 1. Gonadal ridges form ovaries. Differentiation 2. Primordial germ cells become follicles in the cortex of ovaries. 3. mullerian ducts differentiate. o Nothing to degenerate them. 4. wolffian ducts degenerate. o Because there was nothing to promote their development. 5. Genital tubercle gives rise to the clitoris. 6. Urethral groove becomes vestibule. 7. Urethral folds stay unfused and become labia minora. 8. Labioscrotal folds stay unfused and become labia majora. 9. Ovaries also descend, but only to the pelvic brim. FERTILIZATION Sperm fuses with secondary oocyte. Forms zygote, which is a (haploid/diploid) structure. Sperm viable for up to 72 hours & oocyte viable for up to 24 hours. - In order for fertilization to occur, sex can occur up to 3 days before ovulation and 1 day after. Thus, there is a 4 day fertile period in a woman’s body. - IF fertilization occurs, gestation then begins, this is a 280 day process. BARRIERS TO FERTILIZATION loss of sperm from vagina The acidic environment of the vagina Consistency of cervical mucus Phagocytic cells in uterus CAPACITATION Sperm (capable/incapable) of fertilization immediately after ejaculation Membrane changes give sperm ability to fertilize ○ This requires 6-8 hours. Also changes in tail activity ACROSOMAL REACTION Sperm binds with zona pellucida. Acrosomal enzymes release to immediate area Accomplished by 100s of sperm Allows sperm penetration BLOCKS TO POLYSPERMY Fast block ○ membrane depolarization: this means the first sperm to attach causes changes in the membrane permeability Slow block ○ cortical reaction: deals with the release of calcium in the cell enzymes expelled by plasma membrane and destroy sperm receptors oo zona pellucida Water moves, which causes the membrane to push away IMPLANTATION Occurs 6- 7 days after ovulation Takes about a week to implant in the uterus If Fertilized: human chorionic gonadotropin(hCG) maintains the corpus luteum ○ Takes about 3 months to produce the placenta. If NOT Fertilized: the cycle starts over EMBRYONIC MEMBRANES There (is/is not) a direct transfer between mom and baby. The placenta creates a connection between mom and baby. Chorion: (outer/inner) covering surrounding the embryo. ○ Chorionic villi: connect to mom to provide flow of blood and nutrients to the baby Amnion: (outermost/innermost) covering surrounding the embryo. ○ Amniotic fluid: fluid that surrounds the fetus within the amnion protects the baby amniocentesis: removal of amniotic fluid with cannula to be examined chorionic villus sampling: scrape tissue off of chorionic villi ○ used when amniocentesis was thought to be too risky