Chapter 20 *Lecture Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for...

Chapter 20

*Lecture Outline

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

*See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint

without notes.

Chapter 20 Outline• Endocrine Glands and Hormones• Hypothalamic Control of the Endocrine System• Pituitary Gland• Thyroid Gland• Parathyroid Glands• Adrenal Glands• Pancreas• Pineal Gland and Thymus• Endocrine Functions of the Kidneys, Heart, Gastrointestinal

Tract, and Gonads• Aging and the Endocrine System• Development of the Endocrine System

Introduction

• Endocrine glands are ductless organs.• They secrete their molecular products

(hormones) into the bloodstream.• All endocrine organs have an extensive

distribution of many blood vessels.• The endocrine system and the nervous system

both function to communicate signals throughout the body to bring about homeostasis.– Table 20.1 lists similarities and differences between

the two organ systems.

Comparison of the Endocrineand Nervous Systems

Organs of the Endocrine System

Figure 20.1


Ovaries (female)EstrogenInhibinProgesterone

Testes (male)AndrogensInhibin

Pancreatic isletsGlucagonInsulinSomatostatinPancreatic polypeptide

Gastrointestinal (GI) tractCholecystokinin (CCK)Gastric inhibitory peptide (GIP)GastrinSecretinVasoactive intestinal peptide (VIP)

Parathyroid glands(located on posterior surfaceof thyroid)Parathyroid hormone (PTH)

ThymusThymopoietinThymosins

Thyroid glandCalcitonin (CT)Thyroid hormone (TH)

Pineal glandMelatonin

KidneyCalcitriolErythropoietin (EPO)

Adrenal glandsCortex: CorticosteroidsMedulla: Epinephrine (E) Norepinephrine (NE)

HeartAtriopeptin

Pituitary glandAnterior pituitary secretes: Adrenocorticotropic hormone (ACTH) Follicle-stimulating hormone (FSH) Growth hormone (GH) Luteinizing hormone (LH) Melanocyte-stimulating hormone (MSH) Prolactin (PRL) Thyroid-stimulating hormone (TSH)Posterior pituitary releases: Antidiuretic hormone (ADH) Oxytocin (OT)

HypothalamusAntidiuretic hormone (ADH)Oxytocin (OT)Regulatory hormones

Overview of Hormones

• Endocrine glands produce informational molecules called hormones.

• Hormones can only affect cells (target cells) or organs (target organs) that have receptors for a specific hormone.

• Cells or organs that do not possess receptors for a specific hormone do not respond to that hormone.

Classes of Hormones

• The study of the structural components of the endocrine system, the hormones they produce, and the effects of these hormones on target organs is termed endocrinology.

• There are three major classes of hormones based on their chemical structure:

1. Peptide hormones—growth hormone2. Steroid hormones—estrogen3. Biogenic amines—thyroid hormone

Control of Hormone Secretion

• Hormone secretion is regulated by a self-adjusting mechanism called a feedback loop.

• There are two types of feedback loops:1. Negative feedback loop

2. Positive feedback loop

Negative Feedback Loop

• In this type of loop, the stimulus starts the process like an elevation in blood glucose (eating a meal).

• The hormone secreted in response to elevated glucose is insulin.

• Insulin brings about a decrease in blood glucose.

Negative Feedback Loop

Figure 20.2

Positive Feedback Loop

• Only a few examples in the human body

• In this type of loop, the stimulus doesn’t produce an opposite and counteracting effect like a negative feedback loop

• The stimulus accelerates the process

Positive Feedback Loop

Figure 20.2

Hypothalamic Control of the Endocrine System

• The hypothalamus The hypothalamus is the interface between the nervous system and the endocrine system and is the master gland master gland of the endocrine system.

• It controls and oversees most endocrine functions.

• It is located in the inferior region of the diencephalon just superior to the pituitary gland.

Mechanisms of Hypothalamic Control

The hypothalamus controls most endocrine activity in three ways:1. Controls release of regulatory hormones from the anterior pituitary gland2. Secretes oxytocin (OT) and antidiuretic hormone (ADH) from the posterior pituitary gland3. Controls the stimulation and secretion activities of the adrenal medulla

Mechanisms of Hypothalamic Control

Figure 20.3

Pituitary Gland

• Also called the hypophysis

• Located just inferior to the hypothalamus

• Housed within the sella turcica of the sphenoid bone

• Connected to the hypothalamus by a thin stalk called the infundibulum

• Divided into anterior and posterior lobes

Pituitary Gland

Figure 20.4

Anterior Pituitary

• Also known as the adenohypophysis

• Divided into three distinct areas:1. Pars distalis

2. Pars intermedia

3. Pars tuberalis

Control of Anterior Pituitary Hormone Secretions

• Hormones secreted from anterior pituitary gland are regulated by regulatory hormones secreted from the hypothalamus.

• These regulatory hormones from the hypothalamus to the anterior pituitary travel through a blood vessel network called the hypothalamo-hypophyseal portal system.

Regulatory Hormones Secreted by the Hypothalamus

Hypothalamo-Hypophyseal Portal System

Figure 20.6

Hormones of the Anterior Pituitary

There are seven major hormones secreted from the anterior pituitary:1. Thyroid stimulating hormone (TSH)2. Prolactin (PRL)3. Adrenocorticotropin hormone (ACTH)4. Growth hormone (GH)—also called somatotropin5. Follicle stimulating hormone (FSH)6. Lutenizing hormone (LH)7. Melanocyte-stimulating hormone (MSH)

Anterior Pituitary Hormones, Target Organs, and Effects

Figure 20.7


Hypothalamus

Median eminence

Anterior pituitary Posterior pituitary

Thyroid

Mammary gland

Adrenal gland Melanocytes

Ovary

Bone

Muscle

Infundibulum

Thyrotropic cells secretethyroid-stimulating hormone(TSH), which acts on thethyroid gland.

Somatotropic cells secretegrowth hormone (GH), which actson all body tissues, especially bone,muscle, and adipose connective tissue.

Pars intermedia cells secretemelanocyte-stimulating hormone(MSH), which acts on melanocytesin the epidermis.

Gonadotropic cells secretefollicle-stimulating hormone (FSH)and luteinizing hormone (LH)which acts on the gonads (testesand ovaries).

Corticotropic cells secreteadrenocorticotropichormone (ACTH), which actson the adrenal cortex.

Mammotropic cells secreteprolactin (PRL), which acts onmammary glands and testes.

Testis

Adrenalcortex

Testis

Adiposeconnective tissue

Posterior Pituitary

• Derived from the embryonic diencephalon

• Comprised of the following regions:– pars nervosa– infundibular stalk

• Neural connection between the hypothalamus and the posterior pituitary is the hypothalamo-hypophyseal tract

Hypothalamo-Hypophyseal Tract

Figure 20.8


Optic chiasm

Anterior pituitary

Posterior pituitary

Infundibulum

Paraventricular nucleus

Supraoptic nucleus

Hypothalamo-hypophyseal tract

Hypothalamus

Telodendria

Pituitary Gland Hormones

Thyroid Gland

• The largest gland entirely devoted to endocrine activities

• Located just inferior to the thyroid cartilage and anterior to the trachea

• Butterfly shape with right and left lobes connected by a midline isthmus

Thyroid Gland

Figure 20.9

Thyroid Follicle

• Functional unit of the thyroid gland

• Comprised of simple cuboidal cells that produce an iodinated glycoprotein called thyroglobulin (TGB) that is stored internally as a colloid

• The follicle cells and the internal storage area for TGB is collectively called the thyroid follicle

Thyroid Follicle

Figure 20.9


Thyroid cartilage

Thyrohyoid muscle

Common carotid artery

Superior thyroid vessels

Trachea

Parafollicular cellCapillary

Follicular cells

Thyroid follicle

Follicle lumen (contains colloid)

(b)

(a)

Cricoid cartilage

Right lobe of thyroid gland

Left lobe of thyroid gland

Isthmus of thyroid gland

LM 400x

Connectivetissuecapsule

Inferiorthyroid artery

Inferiorthyroid veins

a(right): © The McGraw-Hill Companies, Inc./Photo and Dissection by Christine Eckel; b(right): © The McGraw-Hill Companies, Inc./Photo by Dr. Alvin Telser

Parafollicular Cells

• Large endocrine cells located between thyroid follicles called parafollicular cells

• Secrete calcitonin, which helps to regulate serum calcium

Thyroid Gland–Pituitary Gland Negative Feedback Loop

Figure 20.10


stimulatory

inhibitory

TH

TRH

TSH

1

3

4

5

2

Hypothalamus

TH stimulates target cells to increase metabolicactivities, resulting in an increase in basal bodytemperature.

Increased body temperature is detected by thehypothalamus, and secretion of TRH by thehypothalamus is inhibited. TH also blocks theinteractions of TRH from the hypothalamusand anterior pituitary to prevent the formationof TSH.

Negative feedbackinhibition

A stimulus (e.g., low body temperature)causes the hypothalamus to secretethyrotropin-releasing hormone (TRH),which acts on the anterior pituitary.

Thyrotropic cells in theanterior pituitary releasethyroid-stimulatinghormone (TSH).

TSH stimulates follicular cells of the thyroidgland to release thyroid hormone (TH).

Anteriorpituitary

Target organs in body

Parathyroid Glands

Small glands

(usually four)

embedded on

the posterior

surface of the

thyroid gland

Figure 20.11

Parathyroid Glands

There are two types of cells that are seen in the parathyroid gland:

1. Chief cells (principal cells)—secrete parathyroid hormone (PTH) that helps regulate serum calcium2. Oxyphil cells—function unknown

Cells of the Parathyroid Gland

Figure 20.11


Oxyphil cell

Parathyroid glands

Esophagus

Trachea

Chief cells

Capillary

Oxyphil cells

Chief cells

(a) Posterior view (b) Histologic views

LM 135x

Connective tissue capsuleof parathyroid gland

Thyroid gland(posterior aspect)

Muscles on posteriorside of pharynx

b: © Victor Eroschenko

Parathyroid Hormone

Figure 20.12


Bone

Intestine

Kidney

Bloodstream

PTH molecules

1

4

2

3

Ca2+ ions Low blood calcium (Ca2+) levels aredetected by the parathyroid gland.

Parathyroid hormone (PTH)is secreted into bloodstream.

Rising Ca2+

in blood inhibitsPTH release.

Target organs respond toPTH, or its effects, to increaseblood calcium levels:

• Osteoclasts resorb bone connective tissue, releasing Ca2+ into the bloodstream.

• Kidney retains Ca2+ and promotes activation of an inactive form of vitamin D to calcitriol, an active form of vitamin D.

• Small intestine increases absorption of more Ca2+

under the influence of calcitriol.

Thyroid and Parathyroid Hormones

Adrenal Glands• Paired glands anchored on the superior border

of the two kidneys; also called suprarenal glands

Figure 20.13

Adrenal Glands

• Divided functionally into an outer adrenal cortex and an inner adrenal medulla

Figure 20.13

Adrenal Cortex

Three distinct layers of cells (from superficial to deep):1. Zona glomerulosa—produce mineralocorticoids, the main one being aldosterone2. Zona fasciculata—produce glucocorticoids, the main one being corticosterone3. Zona reticularis—produce the sex hormones, estrogen- and testosterone-related hormones

Adrenal Cortex Hormones

Adrenal Medulla

• Forms the inner core of the adrenal gland• Consists of chromaffin cells, which are

modified cells of the sympathetic division of the autonomic nervous system

• These cells secrete norepinephrine and epinephrine

Figure 20.13

Adrenal Cortex and Medulla

Pancreas

• Located between the duodenum and spleen and posterior to the stomach

Pancreas

Figure 20.14


Duodenum

Gallbladder

Celiac trunk

Spleen

Diaphragm

Liver (cut)

Pancreatic islet

Alpha cell

Beta cell

Delta cell

F cell

Spleen

(a)

Alpha cell

Beta cell

Delta cell

F cell

(b)

Pancreatic islet cells

LM 150x

Inferiorvena cava

Abdominalaorta

Body ofpancreas

Pancreaticducts

Bileduct

Duodenalpapilla

Duodenumof smallintestine

Inferiorvena cava

Tail ofpancreas Pancreatic

acinus

Head ofpancreas

Head ofpancreas

Body ofpancreas

Abdominalaorta

Tail ofpancreas

Pancreaticacini

Leftkidney

Bloodcapillary

a: © The McGraw-Hill Companies, Inc./Photo and Dissection by Christine Eckel; b: © The McGraw-Hill Companies, Inc./Photo by Dr. Alvin Telser

Pancreas

• Both an exocrine (ducted gland) and endocrine (ductless) gland

• About 98–99% of pancreatic cells are pancreatic acini that produce alkaline pancreatic secretions into ducts

• The remaining 1–2% of cells are small clusters of endocrine cells called pancreatic islets (islets of Langerhans)

• The hormones of the islet cells closely regulate the level of blood glucose

Pancreatic Islets

Figure 20.14


Duodenum

Gallbladder

Celiac trunk

Spleen

Diaphragm

Liver (cut)

Pancreatic islet

Alpha cell

Beta cell

Delta cell

F cell

Spleen

(a)

Alpha cell

Beta cell

Delta cell

F cell

(b)

Pancreatic islet cells

LM 150x

Inferiorvena cava

Abdominalaorta

Body ofpancreas

Pancreaticducts

Bileduct

Duodenalpapilla

Duodenumof smallintestine

Inferiorvena cava

Tail ofpancreas Pancreatic

acinus

Head ofpancreas

Head ofpancreas

Body ofpancreas

Abdominalaorta

Tail ofpancreas

Pancreaticacini

Leftkidney

Bloodcapillary

a: © The McGraw-Hill Companies, Inc./Photo and Dissection by Christine Eckel; b: © The McGraw-Hill Companies, Inc./Photo by Dr. Alvin Telser

Pancreatic Islets

Comprised of four different types of endocrine cells, each secreting a different hormone:

1. Alpha cells—secrete glucagon

2. Beta cells—secrete insulin

3. Delta cells—secrete somatostatin

4. F cells—secrete pancreatic polypeptide

Pancreatic Hormones

Pineal Gland

• Secretes melatonin, which is involved in maintaining the 24-hour circadian cycle and sexual maturation

• It is located in the posterior region of the epithalamus

Pineal Gland and Thymus

Figure 20.1


Ovaries (female)EstrogenInhibinProgesterone

Testes (male)AndrogensInhibin

Pancreatic isletsGlucagonInsulinSomatostatinPancreatic polypeptide

Gastrointestinal (GI) tractCholecystokinin (CCK)Gastric inhibitory peptide (GIP)GastrinSecretinVasoactive intestinal peptide (VIP)

Parathyroid glands(located on posterior surfaceof thyroid)Parathyroid hormone (PTH)

ThymusThymopoietinThymosins

Thyroid glandCalcitonin (CT)Thyroid hormone (TH)

Pineal glandMelatonin

KidneyCalcitriolErythropoietin (EPO)

Adrenal glandsCortex: CorticosteroidsMedulla: Epinephrine (E) Norepinephrine (NE)

HeartAtriopeptin

Pituitary glandAnterior pituitary secretes: Adrenocorticotropic hormone (ACTH) Follicle-stimulating hormone (FSH) Growth hormone (GH) Luteinizing hormone (LH) Melanocyte-stimulating hormone (MSH) Prolactin (PRL) Thyroid-stimulating hormone (TSH)Posterior pituitary releases: Antidiuretic hormone (ADH) Oxytocin (OT)

HypothalamusAntidiuretic hormone (ADH)Oxytocin (OT)Regulatory hormones

Thymus

• Located just superior to the heart and just deep to the sternum

• Larger in infants and children than in adults

• Functions in association with the lymphatic system to regulate and maintain body immunity

Other Organs with Endocrine Functions

Pituitary Gland Development

Figure 20.15

Thyroid Gland Development

Figure 20.16

Chapter 20 *Lecture Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for...

Documents

Transcript of Chapter 20 *Lecture Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for...