Endocrine System - Anatomy and Physiology LAB - Lecture Slides, Slides of Physiology

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The Endocrine System

•^

A gland is one or more cells that makesand secretes an aqueous fluid

-^

Classified by:1. Site of product release – endocrine or

exocrine

2. Relative number of cells forming the

What is a gland? gland – unicellular or multicellular

Endocrine System: Overview

•^

Endocrine system

• the body’s second

great controlling system which influencesmetabolic activities of cells by means ofhormones

-^

Endocrine glands

• pituitary, thyroid,

parathyroid, adrenal, pineal, and thymus

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The pancreas and gonads produce bothhormones and exocrine products

How

do

we

call

the

products

of

the

endocrine

glands?

•^

HORMONES:

chemical

“messengers”

that

helps

to

coordinate

and

integrate

the

activity

of

the

body

•^

Hormones,

comes

from

a

Greek

word

meaning

“to

arouse”,

because

they

stimulating

changes

in

their

metabolic

activity.

Types of Hormones

•^

Amino acid based

• most hormones belong

to this class, including:–

Amines, thyroxine, peptide, and proteinhormones

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Steroids

• gonadal and adrenocortical

hormones

-^

Eicosanoids

• leukotrienes and

prostaglandins

Hormone Action

• Hormones alter target cell activity by one of

two mechanisms–

Second messengers involving:

-^

Regulatory G proteins

-^

Amino acid–based hormones

Direct gene activation involving steroidhormones

• The precise response depends on the type

of the target cell. Organs that response to aparticular hormones are referred to as the target organs

Major Endocrine Organs

Figure 16.

• Small gland hanging from the roof of the

third ventricle of the brain

• Secretory product is melatonin• Melatonin is involved with:

Day/night cycles

Physiological processes that show rhythmicvariations (body temperature, sleep,appetite)

Pineal Gland

•^

Pituitary gland

• two-lobed organ that

secretes nine major hormones

-^

Neurohypophysis

• posterior lobe (neural

tissue) and the infundibulum– Receives, stores, and releases hormones from

the hypothalamus

•^

Adenohypophysis

• anterior lobe, made up

of glandular tissue– Synthesizes and secretes a number of

hormones

Pituitary (Hypophysis)

Pituitary-Hypothalamic Relationships:

Anterior Lobe

Adenohypophysis

hormones

(cont)

•^

Growth

hormone

(GH):

Is

a

general

metabolic

hormone

that

plays

and

important

role

in

determining

body

size.

•^

Prolactin:

Stimulates

breast

development

and

promote

and

maintains

lactation

by

the

mammary

glands

after

childbirth.

It

may

stimulate

testosterone

production

in

males.

Figure 16.

Metabolic Action of Growth Hormone

Thyroid and Parathyroid Glands

Figure 16.10a

•^

The largest endocrine gland, located inthe anterior neck

, consists of two lateral

lobes connected by a median tissue masscalled the isthmus

• Composed of follicles that produce the

glycoprotein thyroglobulin

• Colloid (thyroglobulin + iodine) fills the lumen

of the follicles and is the precursor of thyroidhormone

• Other endocrine cells,

the parafollicular

cells, produce the hormone calcitonin

Thyroid Gland