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Endocrine system. 1. General data on endocrine glands Morphofunctional characteristics of the endocrine glands Pituitary gland Epiphysis Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas gonads Organogenesis of the endocrine system
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Endocrine system 1. General data on endocrine glands Morphofunctional characteristics of the endocrine glands Pituitary gland Epiphysis Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas gonads Organogenesis of the endocrine system Lecturer: PhD, professor Tamara Hacina
Characteristics of the endocrine system The endocrine system functions in the regulation of body activities. It acts through chemical messengers called hormones that influence growth, development, metabolic activities. Its action is measured in minutes, hours, or weeks & is more generalized than the action of the nervous system.
The endocrine system • The endocrine system comprises a group of ductless glands that secrete chemical messenger substances, called hormones, into the bloodstream. • Hormones are responsible for the long-term regulation of many bodily functions. • The endocrine system includes the pituitary, thyroid, parathyroid, thymus and adrenal glands, and the pancreas and gonads (ovaries and testes).
Common features of the endocrine glands • Superior blood-supply: fenestrated capillaries,on at least one side • Ductless glands • Cells organized in “chunks”: blocks, islands, plates, cords • Epithelial in origin (an or two exceptions) • Polihedral cells with round nucleus • Plentifull organelle content (indicates synthesis)
The endocrine system acts with nervous system to coordinate the body's activities. • Both systems enable cells to communicate with others by using chemical messengers. • The endocrine system uses chemical messengers called hormones that are transported by the circulatory system (blood). They act on target cells that may be anywhere in the body. • The endocrine system is slower than the nervous system because hormones must travel through the circulatory system to reach their target. • Target cells have receptors that are specific to the signaling molecules. The binding of hormones to the receptors on or within the target cell produces a response by the target cell.
Hormones • Groups of hormones : • Amono acid derivatives: epinephrine, norepinephrine, thyroxine • 2. Small peptides: encephalin, vasopressin, TRH • 3. Proteins: nerve growth factor, insulin, parathormone, TSH, EGF • 4. Steroids: cortisol, progesterone, testosterone, estradial. Hormones are: • chemical messengers • mostly proteins, amines (small molecules derived from amino acids) or steroids • secreted by endocrine glands (glands without ducts) • carried in bloodstream to target organs • change the way in which cells function • target specific
Chemical Classificaton of Hormones • Steroid Hormones: • Lipid soluble • Diffuse through cell membranes • Endocrine organs • Adrenal cortex • Ovaries • Testes • Placenta Receptors for steroid hormones are found in the cell’s cytoplasm or in its nucleus • Nonsteroid Hormones: • Not lipid soluble • Received by receptors external to the cell membrane • Endocrine organs • Thyroid gland • Parathyroid gland • Adrenal medulla • Pituitary gland • pancreas Receptors for nonsteroid hormones are located on the cell membrane
Mechanisms of hormone release (a) Humoral: in response to changing levels of ions or nutrients in the blood (b) Neural: stimulation by nerves (c) Hormonal: stimulation received from other hormones
Hypothalamus Pituitary gland (hypophysis) Pineal body The endocrine and nervous systems are so closely associated that they are collectively called the neuroendocrine system. The main control center is the hypothalamus, also known as the “master switchboard”. Suspended from the hypothalamus by a stalk is the pituitary gland. The hypothalamus sends messages to the pituitary gland, in turn, releases hormones that regulate body functions.
Pineal Gland The pineal gland was called the "third eye" by ancient people. It was thought to have mystical powers. The pineal does contain a complete map of the visual field of the eyes, and it plays several significant roles in human functioning. It is the center for the production of the hormone melatonin. It regulates daily body rhythms, most notably the day/night cycle, prevents jet lag, is implicated in seasonal affective disorder, coordinates fertility, and allows for deep restful sleep patterns. The pineal gland or in its Latin and anatomical name "epiphysis cerebri", is a tiny bean-size brain organ or "gland" which is connected to the brain and nervous systems through a complex network of bidirectional links. The "pineal master gland" acts as a true "director of the hormonal orchestra" in the course of growth, puberty, fertility and aging.
The Pineal Gland • At the end of a short stalk on the roof of the diencephalon • Pinealocytes with dense calcium particles • Can be seen on x-ray (because of Ca++) • Melatonin helps regulate the cardium rhythm • The biological clock of the diurnal (night/day) rhythm • Complicated feedback via retina’s visual input
Why is the Hypothalamus so Important? • Secretes regulatory homones • RH • RIH • "Directs" pituitary
Hypothalamus (general) Connection to pituitary: Neuronal to POSTERIOR PITUITARY Endocrine to ANTERIOR PITUITARY RH = Pituitary releasing hormones RIH = Pituitary release inhibiting hormones
Neurosecretory Cells Specialized neurons Synthesize and secrete hormones Extend from HYPOTHALAMUS to POSTERIOR PITUITARY
Neurosecretory cells in Hypothalamus • Nuclei synthesize and secrete hormones • Neuronal connection to POSTERIOR pituitary • Antidiuretic Hormone (ADH), Oxytocin
Posterior Pituitary Hormones • Manufactured in Hypothalamus, released from Post. Pit. • Oxytocin • Target = smooth ms. Uterus and Breast (&brain) • Function = labor and delivery, milk ejection,(pair bonding) • ADH (Vasopressin AVP) • Target = kidneys • Function = water reabsorption
The pituitary gland, which is located in the center of the skull, just behind the bridge of the nose, is about the size of a pea. It is an important link between the nervous system and the endocrine system and releases many hormones which affect growth, sexual development, metabolism and the system of reproduction. The "hypothalamus" is a tiny cluster of brain cells just above the pituitary gland, which transmits messages from the body to the brain. The pituitary gland has two distinct parts, the anterior and the posterior lobes, each of which releases different hormones which affect bone growth and regulate activity in other glands. This gland was once believed to be the main controlling gland of the body, but we now know that, it is subservient to a master gland called the hypothalamus, which is the needed link between the pituitary gland and the brain. This "master gland" is really a way station between the body and the brain and sorts out messages going to and from the brain. It responds to the body through the pituitary gland, which is suspended just below it. It sometimes replies by nerve impulses and sometimes with needed hormones. The pituitary gland then makes hormones of its own in answer to the body's needs. Pituitary Gland
MASTER GLAND • Anterior and posterior portions • Posterior connected to hypothalamus by infundibulum • Anterior connected via blood stream Pituitary gland
The pituitary gland is: • a pea-sized structure located at the base of the brain. • an extension of the hypothalamus. • consists of an anterior lobe and a posterior lobe. • produces hormones that control other glands and many body functions.
Releasing hormones (factors) of hypothalamus Secreted like neurotransmitters from neuronal axons into capillaries and veins to anterior pituitary (adenohypophysis) TRH (thyroid releasing hormone) - turns on TSH CRH (corticotropin releasing hormone) - turns on ACTH GnRH (gonadotropin releasing hormone) - turns on FSH and LH PRF (prolactin releasing hormone) - turns on PR GHRH (growth hormone releasing hormone) - turns on GH Inhibiting hormones of hypothalmus PIF (prolactin inhibiting factor) -----turns off PRL GH (growth hormone) inhibiting hormone ---turns off GH The hypothalamus controls secretion of hormones which in their turn control the secretion of hormones by the thyroid gland, the adrenal cortex and gonads: in this way the brain controls these endocrine glands
Hypothalamus____ Pituitary______ (hypophysis)
From the posterior pituitary (neuro-hypophysis) • ADH (antidiuretic hormone or vasopressin) stimulates the kidneys to reclaim more water from the urine, raises blood pressure. • Oxytocin prompts contraction of smooth muscle in reproductive tracts, in females initiating labor and ejection of milk from breasts.
Sits in hypophyseal fossa: depression in sella turcica of sphenoid bone The Pituitary Pituitary secretes 9 hormones 1. TSH 2. ACTH 3. FSH 4. LH 5. GH 6. PRL 7. MSH Two divisions: • Anterior pituitary (adenohypophysis) • Posterior pituitary (neurohypophysis) The first four are “tropic” hormones, they regulate the function of other hormones ________ _________________________________________________________________ 8. ADH (antidiuretic hormone), or vasopressin 9. Oxytocin
The pituitary gland Thyroid stimulating hormone Adrenocorticotropic hormone Gonadotropic hormones (FSH & LH) Growth hormone Prolactin Antidiuretic hormone Oxytocin ANTERIOR LOBE POSTERIOR LOBE
Simmonds disease, also known as anterior pituitary hypofunction, is lack secretion of pituitary hormones, lesions of pituitary or hypothalamus involve the endocrine function in pituitary gland. when the pituitary had destroyed, may produce the performance of endocrine gland hypofunction, the mainly involvement of the gland is sex gland, thyroid and adrenal cortex.
The thyroid gland is shaped like a butterfly and usually weighs less than one ounce. The thyroid cartilage covers the larynx and produces the prominence on the neck known as the "Adam's Apple". The thyroid gland controls the rate at which the body produces energy from nutrients. If the body does not get enough iodine, the thyroid gland cannot produce a proper amount of hormones for this conversion process. The result can be a goiter, an enlargement of the thyroid gland. In some parts of the world, iodine is so scarce that most of the population have goiters. Thyroid Gland
Thyroid is composed of spherical follicles • Follicle cells: produce thyroglobulin, the precursor of thryoid hormone (thyroxin) • Colloid lumen is of thyroglobulin • Parafollicular “C” cells: produce calcitonin
Hypersecretion of the thyroid glands at adults
Exophthalmos of Grave’s disease Enlarged thyroid (goiter) from iodine deficiency
1. Cretinism (in infancy) – dwarfs, retarded - hypothyroidism2. Myxedema (in adults) – swelling, slowness - hypothyroidism 3. Regular Goiter – too little iodine yields pituitary response4. Toxic Goiter – TSH overproduction Malfunctions of Thyroid gland
Hyposecretion of the thyroid gland at adults
Parathyroid Glands • There are four parathyroid glands, which are located behind the thyroid. • The sole purpose of the gland is to regulate the calcium level in our bodies within a very narrow range in which our muscular and nervous systems can function properly.
