Transcript Target cells

Endocrine & Reproductive
Systems
Chapter 19 & 27
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Introduction
– The endocrine system consists of cells, tissues,
& organs that secrete hormones into the blood
– Hormone – an organic substance secreted by a
cell that has an effect on the metabolic activity
of another cell or tissue
– Target cells – cells that are affected by the
hormone
• Have specific receptors for the hormones
– Types of hormones
• Steroid
• Amino acid derivative
• Peptide
Human Anatomy, 3rd edition
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How Hormones Work
– Activation of 2nd messengers
• Hormone (first messenger) binds to a receptor on
the plasma membrane
• Receptor/hormone complex activates another
substance in the cell (2nd messenger) which then
triggers the cell’s response
– Activation of genes
• Hormone crosses the cell membrane
• Hormone binds to a receptor in the cytoplasm or the
nucleus
• Receptor/hormone complex binds to the DNA and
alters gene activity
Human Anatomy, 3rd edition
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How Hormones Work
Human Anatomy, 3rd edition
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The Hypothalamus
– Three methods of endocrine regulation
• Sympathetic neurons control the adrenal medulla
• Releases hormones
– Antidiuretic hormone (ADH)
– Oxytocin
• Secretes regulatory hormones (regulatory factors)
that control the anterior pituitary gland
– Releasing factors
– Inhibiting factors
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Hypothalamic Regulation
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Overview of the Endocrine System
Human Anatomy, 3rd edition
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The Pituitary Gland
– aka hypophysis = “growing below”
• Located in sella turcica
• Connected to the hypothalamus by the
infundibulum
– Master gland of the endocrine system
– 2 parts
• Posterior pituitary = Neurohypophysis
– “Nervous part”
• Anterior pituitary = adenohypophysis
– Hypophyseal portal veins supply the anterior pituitary
from the hypothalamus
Human Anatomy, 3rd edition
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Hypophyseal Portal System
– Carries RFs and IFs from the hypothalamus to
the anterior pituitary
– 2 capillary beds connected by portal veins
– Median eminence – neurons secrete regulatory
factors
• Diffuse into fenestrated capillaries
– Portal veins connect to second capillary
network in anterior pituitary
• Releasing factors diffuse out, stimulate surrounding
endocrine cells
Human Anatomy, 3rd edition
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The Pituitary Gland
Human Anatomy, 3rd edition
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Posterior Pituitary Hormones
– Neurohypophysis is nervous tissue
• Cell bodies are in the hypothalamus
– Make hormones
• Axons run down the infundibulum
– Carry hormones to axon terminals
• Axon terminals are in the posterior pituitary
– Store hormones
– Produces 2 hormones
• Antidiuretic hormone (ADH)
– Target – kidneys
– Effect – reabsorption of water
• Oxytocin
– Targets – reproductive organs
– Effects – contractions of smooth muscles (labor contractions,
milk ejection; ductus deferens, prostate gland – ejaculations)
Human Anatomy, 3rd edition
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Anterior Pituitary Hormones
– Gonadotropins stimulate growth &
development of gonads
• Follicle stimulating hormone (FSH) stimulates
gametes
– Targets – follicle cells (females), testes (males)
– Effects – follicle development & estrogen secretion
(females), sperm maturation (males)
• Luteinizing hormone (LH)
– Targets – follicle cells (females), interstitial cells of testes
(males)
– Effects – ovulation, formation of corpus luteum, secretion
of progesterone (females), testosterone secretion (males)
Human Anatomy, 3rd edition
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Anterior Pituitary Hormones
– Thyroid stimulating hormone (TSH)
• Target – thyroid gland
• Effect – triggers the release of thyroid hormones
– Adrenocorticotropic hormone (ACTH)
• Target – adrenal cortex
• Effect – cells that produce steroid hormones called
glucocorticoids
Human Anatomy, 3rd edition
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Anterior Pituitary Hormones
– Prolactin
• Target - breast
• Effect - stimulates milk production
– Growth hormone
• Target – all cells
• Effect - stimulates growth in general and the skeletal
system in particular
– Melanocyte stimulating hormone (MSH)
• Target - melanocytes
• Effect – increases melanin production and
distribution
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Pituitary Hormones
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The Thyroid Gland
– Location – inferior to thyroid cartilage
– Thyroid follicles
• Follicle cells make thyroglobulin (contains tyrosine) &
absorb iodine from the interstitial fluid
• Tyrosine + iodine makes thyroxine (T4) or triiodothyronine
(T3)
• Target cells – most cells
• Effect of thyroid hormones – increase energy utilization,
oxygen consumption, growth, development
• Thyroid hormone release is controlled by TSH from the
anterior pituitary
– Structure also includes C cells
• Produce calcitonin (CT)
• Targets – bone, kidneys
• Effect of calcitonin – lowers blood calcium levels
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The Thyroid Gland
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Thyroid Follicles and C Cells
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Control of Thyroid Hormones
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The Parathyroid Glands
– Location – posterior surfaces of the thyroid
gland
– Principal cells (chief cells) produce
parathyroid hormone (PTH)
– Target cells – bone, kidneys, intestines
– Effect of PTH – increases blood calcium levels
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The Parathyroid Glands
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The Thymus
– Location – posterior to the sternum
– Produces thymosins which enhance
lymphycyte production
– Development
• Childhood – large
• Puberty – largest
• Adulthood – decreases in size
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The Thymus Gland
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The Adrenal Gland
– Location – on top of the kidney
– Structure – outer cortex and inner medulla
– Medulla
• Secretes epinephrine & norepinephrine
• Target – most cells
• Effect
– Epinephrine – increase cardiac activity, blood pressure,
blood glucose; constricts blood vessels in skin, dilates
blood vessels in skeletal & cardiac muscle
– Norepinephrine – increases cardiac activity, constricts
most blood vessels
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The Adrenal Glands
– The adrenal cortex is composed of 3 layers
• Zona glomerulosa secretes mineralocorticoids,
mostly aldosterone
– Target – kidneys
– Effect – increases blood sodium levels, decreases blood
potassium levels
• Zona fasciculata – secretes glucocorticoids
(cortisol, corticosterone)
– Target – most cells
– Effect – conserve blood glucose, anti-inflammatory effects
– Controlled by ACTH
• Zona reticulares – secretes androgens
– Effects are uncertain
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The Adrenal Glands
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The Adrenal Glands
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The Pancreas
– Location – between the spleen and the duodenum
– Its functions are both exocrine and endocrine
– The endocrine cells are in the Islets of Langerhans
• Alpha cells secrete glucagon
– Targets – liver, adipose tissues
– Effect - increase blood sugar levels
• Beta cells secrete insulin
– Most cells
– Effect - decrease blood sugar levels
• Delta cells secrete somatostatin
– Targets – alpha & beta cells, digestive epithelium
– Effect - antagonistic to growth hormone
– Diabetes mellitis
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The Pancreas
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Islet of Langerhans
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The Male Reproductive System
– Sperm are produced in the seminiferous
tubules of the testes (spermatogenesis)
– Sperm are stored in the epidymus, then
transported through the vas deferens, and leave
the body through the urethra
– Seminal fluids (semen) are added to the sperm
by the seminal vesicles, prostate gland, and
bulbourethral gland
Human Anatomy, 3rd edition
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The Male Reproductive System
Human Anatomy, 3rd edition
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Testes
– Interstitial cells secrete androgens (male sex
hormones); testosterone is the most important
• Target – most cells
• Effects – maturation of sperm; protein synthesis in
skeletal muscle; male secondary sex characteristics
& behaviors
– Some interstitial cells secrete inhibin
• Target – anterior pituitary
• Effect – inhibits the secretion of FSH
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The Testes
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Seminiferous Tubules
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Seminiferous Tubule
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The Female Reproductive System
– Ova (oocytes) are produced in the ovaries
(oogenesis)
– Approximately every 28 days one ovum is
expelled from the ovary (ovulation)
– An ovum transported through the fallopian
tube to the uterus where it becomes embedded
in the uterine lining
• Fertilization occurs in the fallopian tube
– If the egg is not fertilized, the uterine lining
detaches and is shed in menstruation
– If the egg is fertilized, the uterine lining is held
in place and supported by progesterone
Human Anatomy, 3rd edition
Prentice Hall, © 2001
The Female Reproductive System
Human Anatomy, 3rd edition
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Ovaries
– Follicle cells secrete estrogen
• Targets – most cells
• Effects – follicle maturation; female secondary sex
characteristics and behaviors
– Follicle cells also secrete inhibin
• Target – anterior pituitary
• Effect – inhibits secretion of FSH
– Corpus luteum secretes progesterone and relaxin
• Progesterone
– Targets – uterus, mammary glands
– Effects – prepare uterus for implantation and mammary glands
for secretion
• Relaxin
– Targets – pubic symphysis, uterus, mammary glands
– Effects – loosens pubic symphysis, relaxes cervical muscles,
stimulates mammary gland development
Human Anatomy, 3rd edition
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Hormonal Regulation of the Female
Reproductive System
Human Anatomy, 3rd edition
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The Pineal Gland
– Location = epithalamus
– Pinealocytes secrete melatonin
• Derived from the neurotransmitter seratonin
• Light inhibits production
– Regulates circadian rythms
• Target – hypothalamus
• Effects – Inhibits the releasing factors that control
FSH & LH secretion
– Slows maturation of sperm, oocytes, & reproductive
organs
Human Anatomy, 3rd edition
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Endocrine Disorders
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