Chapter 18: The Endocrine System BIO 211 Lab Instructor: Dr. Gollwitzer

Today in class we will: Discuss the hypophyseal portal system Describe the endocrine system Identify the organs and tissues of the endocrine system and the locations, associated structures, hormones and the functions of those hormones secreted by each of those endocrine organs, : Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands Discuss the hypophyseal portal system

Endocrine System One of the body’s two coordination/communication systems Nervous system is the other Endocrine glands are ductless glands Communicate with other cells/organs/ systems through release of hormones Endocrine cells  hormone (chemical messenger)  interstitial fluid or circulatory system  target cells  effect(s)

Figure 1–2

Figure 1–2

Endocrine Organs Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pancreas Kidneys Reproductive organs (gonads and placenta) Other: heart, thymus, adipose tissue

Fig 18-1

Pineal Gland Location Contains Pinealocytes  melatonin In posterior roof of third ventricle (epithalamus) Contains Neurons Neuroglia Pinealocytes (special neurosecretory cells) Pinealocytes  melatonin

Pineal Gland Functions of melatonin Time-keeping hormone, e.g., tells body it’s time for sleep Establishes circadian rhythms, e.g., daily changes in body temperature, hormone and enzyme levels Inhibits reproductive function, e.g., decreases at puberty An antioxidant; may protect CNS neurons from free radicals Inhibits MSH (secreted by anterior pituitary)

Pineal Gland Figure 14–11a

Hypothalamus Location Floor of diencephalon, below thalamus and above brainstem (mesencephalon, pons, medulla oblongata) Extends from: Area superior to optic chiasm (where optic nerves arrive at brain) to Posterior margins of mamillary bodies (nuclei in floor of hypothalamus; control feeding reflexes) Infundibulum (slender stalk) connects hypothalamus to pituitary gland Area adjacent/posterior to infundibulum = median eminence

Hypothalamus Figure 14–10a

3 Endocrine Regions of Hypothalamus Supraoptic nuclei  antidiuretic hormone (ADH) Causes water retention at kidneys, increased blood pressure Transported via axons of neurosecretory cells to posterior pituitary for release near fenestrated capillaries Paraventricular nuclei  oxytocin (OT) Stimulates smooth muscle contraction of: Uterus, mammary glands, ductus deferens, prostate gland

3 Endocrine Regions of Hypothalamus Median eminence Swelling near attachment of infundibulum Where hypothalamic neurons  regulatory hormones (RHs) near fenestrated capillaries Transported in blood to anterior pituitary via hypophyseal portal system Stimulate/inhibit cells that produce/secrete hormones

Fig 18-7

Portal System Blood vessels that link 2 capillary networks Capillaries  veins  capillaries  veins  heart vs. usual pattern Heart  arteries  capillaries in organ/tissues  veins  heart Examples Hepatic portal system From GI tract to liver Hypophyseal portal system From hypothalamus to anterior pituitary

Hypophyseal Portal System Capillaries from median eminence unite to form portal vessels (veins) that travel to anterior pituitary capillaries RHs enter hypothalamic blood stream quickly due to fenestrated capillaries Portal system ensures RHs reach pituitary before entering general circulation

Pituitary Gland (Hypophysis) Location In hypophyseal fossa within sella turcica of sphenoid Connected to hypothalamus by infundibulum Held in position by diaphragma sellae Divided into 2 lobes/glands Anterior pituitary (adenohypophysis) Posterior pituitary (neurohypophysis)

Pituitary Gland (Hypophysis) Figure 18–6

Pituitary Gland Hormones Fig 18-9

Posterior Pituitary (Neurohypophysis, Pars Nervosa) Contains axons of hypothalamic neurons (neurosecretory cells) Releases 2 peptide hormones produced in the hypothalamus ADH (antidiuretic hormone) OT (oxytocin)

Anterior Pituitary (Adenohypophysis) Has 3 parts (“pars”) Pars distalis Largest, most anterior Produces/secretes 6 of 7 hormones (not MSH) Pars intermedia Narrow band bordering posterior pituitary Produces/secretes MSH Pars tuberalis Wraps around infundibulum

Anterior Pituitary (Adenohypophysis) Produces and releases 7 peptide hormones ACTH (adrenocorticotropic hormone) Stimulates production/secretion of glucocorticoids (GCs) by adrenal gland TSH (thyroid-stimulating hormone) Triggers secretion of thyroid hormones GH (growth hormone) Stimulates tissue growth PRL (prolactin) Stimulates mammary gland development and milk production

Anterior Pituitary (Adenohypophysis) FSH (follicle-stimulating hormone) A gonadotropin Stimulates ovarian changes, hormone production and egg and sperm development LH (luteinizing hormone, aka interstitial cell- stimulating hormone, ICSH) Another gonadotropin Triggers ovulation and corpus luteum (CL) development in females Hormone production in both sexes MSH (melanocyte-stimulating hormone) Stimulates melanin production by melanocytes in stratum germinativumm of epidermis

Thyroid Gland Location Extensive blood supply gives it red color Curves across anterior surface of trachea, inferior to thyroid cartilage of larynx Extensive blood supply gives it red color Consists of two lobes united by an isthmus Lobes filled with thyroid follicles Spheres formed by simple cuboidal epithelium Cavity contains viscous colloid (proteinaceous fluid) Surrounded by capillary network

Thyroid Gland Fig 18-10a

Fig 18-10b

Thyroid Gland Hormones Follicle cells Simple cuboidal epithelium  T3 and T4 Stimulate tissue metabolism, energy utilization, growth C (clear, parafollicular) cells  Calcitonin Decreases serum Ca++

Parathyroid Glands 2 pairs of glands embedded in posterior surface of thyroid gland Contain principal (chief) cells  PTH (parathyroid hormone) Increases serum Ca++

Parathyroid Glands Fig 18-12a

Today in class we will: Identify the following organs and tissues of the endocrine system and the locations, associated structures, hormones and the functions of those hormones secreted by each of those endocrine organs, : Adrenal glands Pancreas Kidneys Reproductive organs (gonads and placenta) Other: heart, thymus, adipose tissue

Adrenal Glands aka Suprarenal glands Location 2 regions On superior surface of kidneys 2 regions Adrenal cortex  steroid hormones (adrenocortical steroids/ corticosteroids) Adrenal medulla  epinephrine and norepinephrine (E, NE) Under ANS control)

Adrenal Glands Fig 18-14a

Fig 18-14b

Adrenal Cortex 3 Zones  Different Hormones Fig 18-14c

Adrenal Cortex: 3 Zones Zona glomerulosa Zona fasciculata Outer zone, under capsule  mineralocorticoids, e.g., aldosterone Zona fasciculata Middle zone, largest region  glucocorticoids, e.g., cortisol, cortisone Zona reticularis Inner zone, adjacent to medulla  androgens, e.g., testosterone

Pancreas Location Appearance Has endocrine and exocrine functions In J-shaped loop between stomach and duodenum of small intestine Appearance Lumpy 3 parts: Head Body Tail Has endocrine and exocrine functions

Pancreas Figure 18–15

Endocrine Pancreas 1% of volume Small groups of cells scattered among exocrine cells = pancreatic islets (islets of Langerhans) Alpha cells  glucagon   blood glucose Beta cells  insulin   blood glucose

Exocrine Pancreas 99% of volume Clusters of gland cells (pancreatic acini) and ducts Release enzyme-rich digestive juices into small intestine

Kidneys Location Produce hormones On either side of vertebral column Calcitriol Stimulates calcium and phosphate ion absorption from digestive tract Erythropoietin (EPO) Stimulates RBC production by bone marrow

Figure 26–2