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Chapter 9�The Endocrine System

Essentials of Human Anatomy & Physiology

Slides 9.1 – 9.22

Seventh Edition

Elaine N. Marieb

Lecture Slides in PowerPoint by Jerry L. Cook

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Slide 9.1

The Endocrine System

Second messenger system of the body
Uses chemical messages (hormones) that are released into the blood
Hormones control several major processes

Reproduction
Growth and development
Mobilization of body defenses
Maintenance of much of homeostasis
Regulation of metabolism

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Slide 9.2

Hormone Overview

Hormones are produced by specialized cells
Cells secrete hormones into extracellular fluids
Blood transfers hormones to target sites
These hormones regulate the activity of other cells

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Slide 9.3

The Chemistry of Hormones

Amino acid-based hormones

Proteins
Peptides
Amines

Steroids – made from cholesterol
Prostaglandins – made from highly active lipids

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Slide 9.4

Mechanisms of Hormone Action

Hormones affect only certain tissues or organs (target cells or organs)
Target cells must have specific protein receptors
Hormone binding influences the working of the cells

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Slide 9.10

Control of Hormone Release

Hormone levels in the blood are maintained by negative feedback
A stimulus or low hormone levels in the blood triggers the release of more hormone
Hormone release stops once an appropriate level in the blood is reached

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Slide 9.11

Hormonal Stimuli of Endocrine Glands

Endocrine glands are activated by other hormones

Figure 9.2a

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Slide 9.12

Humoral Stimuli of Endocrine Glands

Figure 9.2b

Changing blood levels of certain ions stimulate hormone release

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Slide 9.14

Location of Major Endrocrine Organs

Figure 9.3

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Slide 9.15

Pituitary Gland

Size of a grape
Hangs by a stalk from the hypothalamus
Protected by the sphenoid bone
Has two functional lobes

Anterior pituitary – glandular tissue
Posterior pituitary – nervous tissue

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Slide 9.16

Hormones of the Anterior Pituitary

Six anterior pituitary hormones

Two affect non-endocrine targets
Four stimulate other endocrine glands (tropic hormones)

Characteristics of all anterior pituitary hormones

Proteins (or peptides)
Act through second-messenger systems
Regulated by hormonal stimuli, mostly negative feedback

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Slide 9.17

Hormones of the Anterior Pituitary

Figure 9.4

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Slide 9.18

Growth Hormone (GH)

General metabolic hormone
Major effects are directed to growth of skeletal muscles and long bones
Causes amino acids to be built into proteins
Causes fats to be broken down for a source of energy

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Slide 9.19

Functions of Other Anterior Pituitary Hormones

Prolactin (PRL)

Stimulates and maintains milk production following childbirth
Function in males is unknown

Adrenocorticotropic hormone (ACTH)

Regulates endocrine activity of the adrenal cortex

Thyroid-stimulating hormone (TSH)

Influences growth and activity of the thyroid

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Slide 9.20a

Functions of Other Anterior Pituitary Hormones

Gonadotropic hormones

Regulate hormonal activity of the gonads

Follicle-stimulating hormone (FSH)

Stimulates follicle development in ovaries
Stimulates sperm development in testes

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Slide 9.20b

Functions of Other Anterior Pituitary Hormones

Gonadotropic hormones (continued)

Luteinizing hormone (LH)

Triggers ovulation
Causes ruptured follicle to become the corpus luteum
Stimulates testosterone production in males

Referred to as interstitial cell-stimulating hormone (ICSH)

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Slide 9.22

Hormones of the Posterior Pituitary

Oxytocin

Stimulates contractions of the uterus during labor
Causes milk ejection

Antidiuretic hormone (ADH)

Can inhibit urine production
In large amounts, causes vasoconstriction leading to increased blood pressure (vasopressin)

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Slide 9.22b

Hormones of the Posterior Pituitary

Figure 9.5

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Slide 9.23a

Thyroid Gland

Found at the base of the throat
Consists of two lobes and a connecting isthmus
Produces two hormones

Thyroid hormone
Calcitonin

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Slide 9.23b

Thyroid Gland

Figure 9.6

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Slide 9.24

Thyroid Hormone

Major metabolic hormone
Composed of two active iodine-containing hormones

Thyroxine (T₄) – secreted by thyroid follicles
Triiodothyronine (T₃) – conversion of T₄ at target tissues

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Slide 9.25

Calcitonin

Decreases blood calcium levels by causing its deposition on bone
Antagonistic to parathyroid hormone
Produced by C (parafollicular) cells

Figure 9.9

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Slide 9.26

Parathyroid Glands

Tiny masses on the posterior of the thyroid
Secrete parathyroid hormone

Stimulate osterclasts to remove calcium from bone
Stimulate the kidneys and intestine to absorb more calcium
Raise calcium levels in the blood

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Slide 9.27

Adrenal Glands

Two glands

Cortex – outer glandular region in three layers
Medulla – inner neural tissue region

Sits on top of the kidneys

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Slide 9.28a

Hormones of the Adrenal Cortex

Mineralocorticoids (mainly aldosterone)

Produced in outer adrenal cortex
Regulate mineral content in blood, water, and electrolyte balance
Target organ is the kidney
Production stimulated by renin and aldosterone
Production inhibited by atrial natriuretic peptide

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Slide 9.28b

Hormones of the Adrenal Cortex

Figure 9.10

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Slide 9.29a

Hormones of the Adrenal Cortex

Glucocorticoids (including cortisone and cortisol)

Produced in the middle layer of the adrenal cortex
Promote normal cell metabolism
Help resist long-term stressors
Released in response to increased blood levels of ACTH

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Slide 9.29b

Hormones of the Adrenal Cortex

Sex hormones

Produced in the inner layer of the adrenal cortex
Androgens (male) and some estrogen (female)

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Slide 9.30

Hormones of the Adrenal Medulla

Produces two similar hormones (catecholamines)

Epinephrine
Norepinephrine

These hormones prepare the body to deal with short-term stress

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Slide 9.32a

Pancreatic Islets

The pancreas is a mixed gland
The islets of the pancreas produce hormones

Insulin – allows glucose to cross plasma membranes into cells from beta cells
Glucagon – allows glucose to enter the blood from alpha cells
These hormones are antagonists that maintain blood sugar homeostasis

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Slide 9.32b

Pancreatic Islets

Figure 9.13

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Slide 9.33

Pancreatic Hormones and Blood Sugar

Figure 9.14

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Slide 9.34

Pineal Gland

Found on the third ventricle of the brain
Secretes melatonin

Helps establish the body’s wake and sleep cycles
May have other as-yet-unsubstantiated functions

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Slide 9.35

Thymus

Located posterior to the sternum
Largest in infants and children
Produces thymosin

Matures some types of white blood cells
Important in developing the immune system

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Slide 9.36

Hormones of the Ovaries

Estrogens

Produced by Graafian follicles or the placenta
Stimulates the development of secondary female characteristics
Matures female reproductive organs
Helps prepare the uterus to receive a fertilized egg
Helps maintain pregnancy
Prepares the breasts to produce milk

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Slide 9.37

Hormones of the Ovaries

Progesterone

Produced by the corpus luteum
Acts with estrogen to bring about the menstrual cycle
Helps in the implantation of an embryo in the uterus

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Slide 9.38

Hormones of the Testes

Interstitial cells of testes are hormone-producing
Produce several androgens
Testosterone is the most important androgen

Responsible for adult male secondary sex characteristics
Promotes growth and maturation of male reproductive system
Required for sperm cell production

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Slide 9.39

Other Hormone-Producing Tissues and Organs

Parts of the small intestine
Parts of the stomach
Kidneys
Heart
Many other areas have scattered endocrine cells

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Slide 9.40

Endocrine Function of the Placenta

Produces hormones that maintain the pregnancy
Some hormones play a part in the delivery of the baby
Produces HCG in addition to estrogen, progesterone, and other hormones

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Slide 9.41

Developmental Aspects of the Endocrine System

Most endocrine organs operate smoothly until old age

Menopause is brought about by lack of efficiency of the ovaries
Problems associated with reduced estrogen are common
Growth hormone production declines with age
Many endocrine glands decrease output with age