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Testes (male)

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Male gonads contained in a cutaneous sac called the scrotum Made of: Seminiferous tubules Produced spermatozoa Interstitial cells Produce androgens, such as testosterone

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Ovaries (female)

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Female gonads located near the kidneys Produce the female reproductive cell, the ovum, as well as estrogen and progestin hormones Ovarian cycles are controlled by two anterior pituitary hormones: Follicle Stimulating Hormone (FSH) Luteinizing Hormone (LH)

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Thyroid Gland

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Located within the neck near the larynx, hormones produced are necessary for growth and reproduction, they also regulate lipid and carbohydrate metabolism, affect heat production in the body, and affect metabolic and immune functions

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Pancreas

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Long, flat, abdominal organ located near the duodenum Exocrine functions Produces digestive enzymes Endocrine functions Makes insulin

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Parathyroid Glands

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Several small, pale nodules in, on, or near the thyroid gland, Produces parathyroid hormone (PTH)

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Adrenal Glands

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Located near the cranial ends of the kidneys Consists of an outer adrenal cortex and an inner adrenal medulla

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Endocrine glands

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Basic units of the endocrine system

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Target

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A cell that has receptors for a particular hormone

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Negative Feedback System

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Controls hormone secretion

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TSH (Thyroid-Stimulating Hormone)

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Produced by the anterior pituitary gland, stimulates the thyroid gland to produce more thyroid hormones

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Thyroid Feedback Mechanism

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Low blood thyroid hormone > hypothalamus releases TRH > stimulates pituitary gland to release TSH > thyroid produces T3 and T4

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Hypothalamus

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Controls appetite, body temperature regulation, controls wake-sleep cycles, connects higher centers in the cerebral cortex with lower brain centers and the endocrine system

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Releasing factors

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causes the anterior pituitary to produce and release a particular hormones

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Inhibiting factors

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inhibits the anterior pituitary from producing and releasing a particular hormone

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Pituitary portal system

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A system of tiny blood vessels that links the hypothalamus with the anterior portion of the pituitary gland

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Pituitary Gland (Hypophysis)

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Its hormones direct the activity of other endocrine glands around the body, Located in the pituitary fossa (a small pocket in the sphenoid bone of the skull)

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Anterior Pituitary (Adenohypophysis)

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Developed from glandular tissue, produces the following hormones: Growth Hormone Prolactin Thyroid-Stimulating Hormone Adrenocorticotropic Hormone Follicle-Stimulating Hormone Luteinizing Hormone Melanocyte-Stimulating Hormone

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Posterior Pituitary (Neurohypophysis)

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Developed from nervous tissue, does NOT produce hormones

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Growth Hormone (GH) (Somatotropin; Somatotropic Hormone)

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Helps regulate the metabolism of proteins, carbohydrates, and lipids in all of the body's cells Encourages anabolism (synthesis) of proteins by body cells Causes the mobilization (release) of lipids from storage in adipose tissue and their catabolism (breakdown) in body cells for energy production Discourages the cells from using carbohydrates (e.g. glucose) as energy sources, which causes hyperglycemia

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Growth Hormone Deficiency

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Causes dwarfism, alopecia (hair loss), thin skin, Treated with growth hormone

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Growth Hormone Excess

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Causes acromegaly (giantism), Generally caused by a pituitary tumor

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Bovine Somatotropin

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A synthetic GH-like drug, Used in dairy cows to increase milk production, Causes elevated body temperatures, reduced conception rates, increased risk of mastitis, and increased risk of digestive disorders in cows

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Prolactin

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Helps trigger and maintain lactation (secretion of milk from the mammary glands) in the female Produced and released by the anterior pituitary gland as long as the teat or nipple continues to be stimulated by nursing or milking

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Thyroid-Stimulating Hormone (TSH) (Thyrotropic Hormone)

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Stimulates the growth and development of the thyroid gland and causes it to produce its hormones Increased TSH secretion increases thyroid hormone production and vice versa

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Adrenocorticotropic Hormone (ACTH)

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Stimulates the growth and development of the cortex (outer portion) of the adrenal gland and the release of its hormones Its production is generally regulated by feedback from the hormones of the adrenal cortex ACTH can be released quickly in times of stress when the hypothalamus is stimulated by other parts of the brain, which releases ACTH-releasing factor down to the anterior pituitary gland

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Follicle-Stimulating Hormone (FSH)

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A gonadotropin (stimulates growth and development of the gonads), Stimulates ovulation in females FSH release from the anterior pituitary is stimulated by gonadotropin releasing hormone (GnRH), which is released from the hypothalamus

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Luteinizing Hormone (LH)

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A gonadotropin (stimulates growth and development of the gonads) LH release from the anterior pituitary is stimulated by gonadotropin releasing hormone (GnRH), which is released from the hypothalamus

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corpus luteum

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produces progesterone which is necessary for the maintenance of pregnancy should it occur

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Melanocyte-Stimulating Hormone (MSH)

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Influences the pigment cells of the skin (the melanocytes), Its precise role in the body of mammals is not well understood

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Antidiuretic Hormone (ADH)

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Helps prevent diuresis (the loss of large quantities of water in the urine) Released when the hypothalamus detects the animal is dehydrated

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Diabetes insipidus

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Caused by a deficiency of ADH Causes polyuria and polydipsia Causes dilute urine

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Oxytocin

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Produced in the hypothalamus and then stored and released from the posterior pituitary gland At the time of breeding, it stimulates strong contractions of the myometrium (the muscle of the uterus) that aid in the transport of spermatozoa up to the oviducts When parturition (birthing) begins, it stimulates strong uterine contractions that aid in the delivery of the fetus and the placenta Stimulates contraction of the myoepithelial cells of the lactating mammary gland which causes milk letdown in active mammary glands within one to two minutes after the teat or nipple is stimulated by nursing or milking

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Thyroid Gland

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Consists of two lobes on either side of the larynx that may be connected by a narrow band, called an isthmus, in some species Composed of microscopic follicles that are spheres of simple cuboidal glandular cells that surround a globule of thyroid hormone precursor called colloid

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Thyroid Hormones

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T3, T4, Calcitonin Allow an animal to generate heat and maintain a constant internal body temperature Production can be inhibited by emotional or physical stress Necessary for normal growth and development in young animals - it influences the development and maturation of the CNS and the growth and development of muscles and bones Encourages the anabolism, or synthesis, of proteins if the diet contains adequate energy sources If the diet is deficient in energy sources, encourages catabolism, or breakdown, of protein Causes a hyperglycemic effect when carbohydrates are metabolized Encourages catabolism of lipids

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Calcitonin

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Produced by C cells located between the thyroid follicles Involved in maintaining homeostasis of blood calcium levels Helps prevent hypercalcemia (high blood calcium levels) by decreasing blood calcium levels if it gets to high by encouraging its deposition in bones

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T3

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help regulate the body's metabolic rate, main thyroid hormone, AKA triiodothyronine

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T4

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converted to T3 before producing an effect on target cells AKA tetraiodothyronine; thyroxine

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parathyroid hormone (PTH)

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Prevents hypocalcemia (low blood calcium levels) by increasing the blood calcium level if it falls too low Causes the kidneys to retain calcium and the intestines to absorb calcium from food Withdraws calcium from the bones

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Adrenal cortex

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Developed from glandular tissue Produces glucocorticoid hormones, mineralocorticoid hormones, and sex hormones (all steroids)

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Adrenal medulla

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Developed from nervous tissue Produces the hormones epinephrine and norepinephrine which are involved in the fight-or-flight response

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Glucocorticoid hormones

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Cortisone, Cortisol, Corticosterone Have a hyperglycemic effect, Help maintain blood pressure, Help the body resist the effects of stress Long-term use of glucocorticoid medications will suppress the immune system

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Mineralocorticoid hormones

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Aldosterone

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Aldosterone

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Affects the levels of sodium, potassium, and hydrogen ions in the body Targets the kidneys, where it causes sodium ions to be reabsorbed from the urine back into the blood stream in exchange for potassium and hydrogen ions, which pass out of the body in the urine Affects water levels in the body in that water accompanies sodium back into the bloodstream when sodium ions are reabsorbed

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Androgens

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male sex hormones

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Estrogens

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female sex hormones

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Pancreatic Islets (Islets of Langerhans)

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Endocrine portion of the pancreas Composed of thousands of microscopic clumps of cells scattered throughout the organ

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Insulin

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Produced by beta cells of the pancreatic islets Main action is to allow glucose to be absorbed into body cells and used for energy, which decreases the level of glucose in the blood Glucose can be used in anaerobic metabolism

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Glucagon

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Produced by alpha cells of the pancreatic islets Raises blood glucose by stimulating liver cells to convert glycogen (a storage form of glucose) to glucose and by stimulating gluconeogenesis (the conversion of fat and protein breakdown products to glucose)

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Pancreatic Hormones

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Glucagon, Insulin, Somatostatin

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Somatostatin

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Produced by delta cells of the pancreatic islets Inhibits the secretion of insulin, glucagon, and GH and diminishes the activity of the GI tract

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Production of androgens

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the interstitial cells is stimulated by the anterior pituitary hormone, luteinizing hormone (LH) (also called interstitial cell stimulating hormone (ICSH))

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Testosterone

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the major male sex hormone, is responsible for: The muscular male body shape The male libido (sex drive) Stimulating the development of male accessory sex glands Activating spermatogenesis (spermatozoa production) Stimulating the growth of the penis Stimulating the buildup of proteins in muscle and bone

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Estrogen (Estradiol and Estrone)

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Responsible for the physical and behavioral changes that prepare the female for breeding and pregnancy and signal the male that breeding time is approaching

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Estrogen Production

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FSH stimulates follicles to develop in the ovaries> Follicles are fluid filled, blister-like structures in which the ova develop> The cells that make up the follicle produce and release estrogens into the blood stream> As the follicle grows, more and more estrogen is produced, which causes the anterior pituitary to reduce the production of FSH and increase the production of LH> When the follicle is fully mature, the LH level peaks and, in most species, ovulation occurs> Ovulation is the rupture of the follicle with release of the ovum into the oviduct

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Progestins

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After ovulation has taken place, the high LH levels stimulate the cells of the now-empty follicle to multiply and develop into a solid, hormone-producing structure called the corpus luteum (CL or yellow body)

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progesterone

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helps prepare the uterus to receive the fertilized ovum and is necessary for pregnancy to be maintained once the fertilized ovum implants in the uterus

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Kidneys

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Produce erythropoietin

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Erythropoien

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hormone that stimulates red blood cell production in the bone marrow, production is stimulated by hypoxia

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Stomach

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produces Gastrin

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Gastrin

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Produced in the stomach wall and acts on the stomach wall Secretion is stimulated by the presence of food in the stomach Stimulates gastric glands to secrete hydrochloric acid and digestive enzymes Encourages muscular contractions of the stomach wall

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Small Intestine

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produces Secretin and Cholecystokinin

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Secretin

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Stimulates the pancreas to secrete fluid rich in sodium bicarbonate into the duodenum to neutralize the acidic chyme (partially digested food) from the stomach

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Cholecystokinin

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Stimulates the release of digestive enzymes from the pancreas into the duodenum

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Placenta

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The life-support system for a developing fetus A multilayered, fluid-filled, membranous sac that surrounds the fetus and links it to the blood supply of the uterus Produces a small amount of estrogen and progesterone Produces significant amounts of chorionic gonadotropin in the human and the horse and small amounts in the dog, cat, and cow

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chorionic gonadotropin

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Used to detect pregnancy in the human and horse

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Thymus

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An organ that is important in the development of a young animal's immune system Helps fight of bacteria and viruses Extends cranially from the level of the heart in the thorax up into the neck region along both sides of the trachea, often up to the level of the larynx Produces hormone-like substances called thymopoietin and thymosin

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thymopoietin and thymosin

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Cause primitive cells in the thymus and other lymphoid organs to be transformed into T lymphocytes (T cells)

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Pineal Body

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A structure in the brain located at the caudal end of the deep cleft that separates the two hemispheres of the cerebrum, just rostral to the cerebellum, Produces melatonin

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Melatonin

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Appears to influence the body's biological clock and affects moods and wake-sleep cycles

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Prostaglandins (PGs)

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Hormone-like substances that are produced and exert many effects locally in a variety of body tissues, sometimes called tissue hormones Influence blood pressure, GI tract functions, respiratory functions, kidney functions, blood clotting, inflammation, and reproductive functions

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PGE

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Plays a role in the initiation of inflammation Nonsteroidal Antiinflammatory Drugs (NSAIDs) inhibit PGE synthesis

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PGF2

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drug: dinoprost tromethamine (Lutalyse®) If administered to a female animal that has a functional CL in her ovary, it will destroy the CL and will often cause a new estrous cycle to begin. Can terminate early pregnancy Used to synchronize estrous cycles in livestock species so that groups of animals can be bred together

Endocrine System Vet. Anatomy and Physiology – Flashcards

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