NGRTCI Endocrine System Anatomy

JOFRED M. MARTINEZ

God the Father

Creator of all things

living and no-living

true source of light and wisdom

enlighten our heart and mind

to follow your will today

help us to avoid confusions

and lead us to clarification

let your sublime wisdom

penetrate our humanity…

and your light

shine our dark parts

give us the source of inspiration

that we may become also

an inspiration to others.

we ask this through Christ our Lord

AMEN.

The cells, tissues, and organs are called

endocrine glands

• They are ductless

• They use the bloodstream

• They secrete hormones

• There are also similar glands called

paracrine and autocrine glands that

are quasi-endocrine

Glands that secrete substances are the

exocrine glands

• They have ducts

• They deliver their products directly to

a specific site

Hormone secretion

(a)

(b)

Blood flow

Skin

Duct

Thyroid

gland

Endocrine

gland

Endocrine

cell

Exocrine gland

(sweat gland)

Exocrine

cells

Nerve impulse

Bloodstream

Neuron

transmits

nerve

impulse

Glandular

cells secrete

hormone into

bloodstream

Neurotransmitter

released into

synapse

Post-

synaptic

cell responds

Target cells

(cells with hormone

receptors) respond

to hormone

Hormones have no

effect on other cells

Hypothalamus

Pituitary gland

Thyroid gland

Thymus

Adrenal gland

Pancreas

Parathyroid gland

Pineal gland

Kidney

Testis

(in male)

Ovary

(in female)

Chemically, hormones are either:

• Lipid-soluble Hormones

Steroid hormones

Thyroid hormones

Nitric oxide (NO)

• Water-soluble Hormones

Amine hormones

Peptide hormones and protein

hormones

Eicosanoid hormones

1. Hormonal mechanism: for example, the hypothalamus secretes

hormones that stimulate the anterior pituitary gland to secrete

hormones that stimulate other endocrine glands to secrete

hormones.

2. Humoral mechanism: for example, capillary blood contains a low

concentration of calcium that stimulates secretion of parathyroid

hormone. Parathyroid hormone makes serum calcium go up.

3. Neural mechanism: preganglionic SNS fiber stimulates the

adrenal medulla cells to secrete catecholamines.

Nervous system

Target cells

Action

Target cells

Action

–

– – –

Anterior pituitary gland

Action

Hypothalamus

Peripheral

endocrine

gland

Target cells

Endocrine

gland

Changing level

of substance

in plasma

Endocrine

gland

ORTICOTROPIN-RELEASING HORMONE

HYROTROPIN-RELEASING HORMONE

ROWTH HORMONE-RELEASING HORMONE

ONADOTROPIN-RELEASING HORMONE

ROLACTIN - INHIBITING HORMONE

ROWTH HORMONE- INHIBITORY HORMONE

ELANOCYTE - STIMULATING HORMONE

Optic nerve

Sphenoid bone

Hypothalamus

Optic chiasma

Sella turcica

Third ventricle

Trochlear nerve

Basilar artery

Anterior cerebral

artery

Pituitary stalk

(Infundibulum)

Anterior lobe

of pituitary gland

Sphenoidal

sinus

Posterior lobe

of pituitary

gland

Oculomotor

nerve

DRENOCORTICOTROPIC HORMONE

UTEINIZING HORMONE

OLLICLE-STIMULATING HORMONE

ROWTH / SOMATOTROPIC HORMONE

HYROID-STIMULATING HORMONE

ROLACTIN / LACTOGENIC HORMONE

ELANOCYTE-STIMULATING HORMONE

• Growth hormone (GH): controls growth and protein,

carbohydrate, and lipid metabolism. Production of growth

hormone is controlled by two other hormones:

1. Somatostatin: inhibits growth hormone.

2. Somatotropin: stimulates secretion of growth hormone.

• The majority of growth hormone is secreted during sleep. Other

factors that increase secretion of growth hormone are exercise,

stress, hypoglycemia, starvation, and hypothyroidism.

1. Prolactin: stimulates breast growth and production of milk.

2. FSH: stimulates development of egg and sperm and secretion

of sex hormones.

3. LH: stimulates the production of progesterone and regulates

ovulation in women, and regulates testicular growth,

testosterone production, and androgen production in men.

To stimulate the release of these gonadotropic

hormones, gonadotropin-releasing hormone (GnRH)

must be present.

Important for cervical dilatation prior to birth, and helps the uterus to

contract during labor and delivery, especially during the second and

third stages. In breast-feeding (lactating) mothers, oxytocin causes

milk to be “let down” into area of breast where baby can suckle and

receive milk.

When ADH is secreted, WATER is retained in the vascular space.

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

Follicular cells

Colloid

Extrafollicular

cells

© Fred Hossler/Visuals Unlimited

Larynx Colloid

Isthmus

(a)

(b)

Thyroid

gland Follicular

cell

Extrafollicular

cell


When thinking about thyroid hormones think energy

and metabolism!

1. Increases the metabolism of protein, fat, and glucose.

2. Increases body temperature in response to an elevated

metabolism, which produces body heat.

3. Increases the use of oxygen as metabolism increases.

4. Aids in the development of the neural and skeletal systems in

fetuses.

5. Helps regulate secretion of growth hormone.

6. Aids in production of red blood cells.

7. Affects respiratory rate: too much thyroid hormone increases

respiratory rate, and too little decreases respiratory rate.

8. Aids in normal growth and development.

• Both T3 and T4 increase metabolic rate of cells and tissues.

• T4 is the precursor to T3.

• T3 regulates the metabolic rate of all cells and all processes of cell

growth and tissue differentiation.

• T3 and T4 indirectly increase blood glucose levels.

• Being cold increases the conversion of T4 to T3.

• Things such as stress, starvation, certain dyes, and certain drugs

like steroids, beta-blockers, PTU (propylthiouracil), and

amiodarone decrease the conversion of T4 to T3.

• Targets the bones, kidneys, and epithelial cells of the intestines.

• Decreases blood/serum calcium in three ways:

1. Decreases intestines’ ability to absorb calcium.

2. Decreases osteoclast activity in the bones.

3. Decreases calcium resorption from the kidney tubules.

Bone resorption occurs when osteoclasts break down

bone and release calcium from the bone into the

blood.

Posterior view

Esophagus

Pharynx

Thyroid

gland

Parathyroid

glands

Trachea


Secretory cells

Capillaries


© R. Calentine/Visuals Unlimited

Liver

Intestinal enzymes

Ultraviolet light in skin

Kidney Stimulated by PTH

Hydroxycholecalciferol

Foods

Ca+2

Ca+2

Ca+2

Cholesterol

Provitamin D

Vitamin D

(Cholecalciferol)

Also obtained directly

from foods

Dihydroxycholecalciferol

(active form of vitamin D)

Controls absorption of

calcium in intestine

• Parathyroid hormone (PTH) makes

the serum calcium level go up!

• Too much PTH

hyperparathyroidism

hypercalcemia,

hypophosphatemia, bone damage,

and renal damage.

• Too little PTH hypoparathyroidism,

hypocalcemia,

hyperphosphatemia, hyperreflexia,

and cognitive changes (altered

sensorium).


PTH Ca+2

+ PTH

PTH

Ca+2

+ Ca+2

Bloodstream

– Stimulation

Inhibition

Release into

bloodstream

Parathyroid glands (on

posterior of thyroid gland)

Decreased blood calcium

stimulates parathyroid

hormone secretion

Increased blood

calcium inhibits

PTH secretion

Kidneys

conserve Ca+2 and

activate Vitamin D

Bone

releases Ca+2

Intestine

absorbs Ca+2

Active

Vitamin D

Co

rte

x

Me

du

lla

Capsule

Zona

glomerulosa

Zona

fasciculata

Zona

reticularis

Chromaffin

cells


© Ed Reschke

Adrenal gland

Kidney

Adrenal cortex

(a)

Zona

lomerulosa

Connective

tissue capsule

(b)

Zona

fasciculata

Zona

reticularis

Adrenal

medulla

Adrenal

cortex

Adrenal

medulla

Surface of

adrenal gland


Many heart attacks occur during the early morning hours when

people are coming out of REM sleep, as this is a very stressful

time for the body.

1. Stimulate gluconeogenesis (the formation of carbohydrates from

proteins and other substances by the liver).

2. Provide amino acids and glucose during times of stress.

3. Suppress the immune system due to powerful immunosuppressive

and anti-inflammatory properties.

4. Stimulate fat breakdown.

An increase in aldosterone secretion is also caused by:

• Low fluid volume levels in the vascular space as in shock or

hypovolemia.

• High blood levels of potassium.

The illnesses associated with aldosterone are:

• Hyperaldosteronism (Conn’s syndrome)

• Hypoaldosteronism

Sex hormones are usually broken down into three categories:

1. Androgens, testosterone being the main one.

2. Estrogens, estradiol being the main one.

3. Progestagens, progesterone being the main one.

Synthetic androgens (sex hormones) are referred to

as anabolic steroids.


Pancreatic islet (Islet of Langerhans)

From Kent M. Van De Graaff and Stuart Ira Fox, Concepts of Human Anatomy and

Physiology, 2nd ed. ©1989 Wm. C. Brown Publishers, Dubuque, Iowa. All Rights

Reserved. Reprinted with permission


Gallbladder Common bile duct

Pancreatic duct

Pancreas Duct

Capillary

Small

intestine

Digestive enzyme-

secreting cells

Pancreatic islet

(Islet of Langerhans)

Hormone-secreting

islet cells

too high

too low

Control center

Beta cells secrete

insulin

Receptors

Beta cells detect a rise

in blood glucose

Effectors

Insulin

• Promotes movement of glucose

into certain cells

• Stimulates formation of glycogen

from glucose

Stimulus

Rise in blood glucose

Response

Blood glucose drops toward

normal (and inhibits insulin

secretion)

Normal

blood glucose

concentration

Stimulus

Drop in blood glucose

Response

Blood glucose rises toward

normal (and inhibits glucagon

secretion)

Receptors

Alpha cells detect a drop

in blood glucose

Effectors

Glucagon

• Stimulates cells to break down glycogen

into glucose

• Stimulates cells to convert

noncarbohydrates into glucose

Control center

Alpha cells secrete

glucagon

Pineal Gland

• Secretes melatonin

• Regulates circadian rhythms

Thymus Gland

• Secretes thymosins

• Promotes development of certain lymphocytes

• Important in role of immunity

Reproductive Organs

• Ovaries produce estrogens and progesterone

• Testes produce testosterone

• Placenta produces estrogens, progesterone, and

gonadotropin

Other organs: digestive glands, heart, and kidney

Sympathetic impulses

CRH released

ACTH released

Cortisol released

Long-term adjustment or resistance stage

• Increase in blood concentration of amino acids.

• Increased release of fatty acids.

• Blood glucose increases.

• Blood glycerol and fatty acids increase.

• Heart rate increases.

• Blood pressure rises.

• Breathing rate increases.

• Air passages dilate.

• Pupils dilate.

Anterior pituitary

Hypothalamus

Adrenal cortex

Adrenal medulla

Neural signals

Hormonal signals Stress results from changes

in the external environment

Signals from

sensory receptors

Epinephrine and

norepinephrine

released

Norepinephrine

released

Short-term “fight or flight” or alarm stage.

• Blood flow redistributes.

• Increased glucose formed from

noncarbohydrates—amino acids (from

proteins) and glycerol (from fats).

• Endocrine glands decrease in size

• Muscular strength decreases as GH levels decrease

• ADH levels increase due to slower break down in liver and

kidneys

• Calcitonin levels decrease; increase risk of osteoporosis

• PTH level changes contribute to risk of osteoporosis

• Insulin resistance may develop

• Changes in melatonin secretion affect the body clock

• Thymosin production declines increasing risk of infections

test Normal values significance Thyroid-stimulating

hormone

0.5–5.0 U/mL ↑ in primary hypothyroidism

↓in primary hyperthyroidism

Triiodothyronine (T3) 80–200 ng/100 mL ↓ in hypothyroidism

↑ in hyperthyroidism

Thyroxine (T4 ) 4–12 g/100 mL ↓ in hypothyroidism

↑ in hyperthyroidism

test Normal values significance Parathyroid

hormone

25 pg/mL ↑ in primary hyperparathyroidism

↓ in primary hypoparathyroidism,

parathyroid trauma during thyroid

surgery

Calcium 8.5–10.5 mg/100 mL ↑ in some cancers,

hyperparathyroidism

↓ in hypothyroidism

Phosphorus 2.4–4.7 mg/dL ↑ in hypoparathyroidism

↓ in hyperparathyroidism

test Normal values significance Growth hormone 5 ng/mL ↑ in acromegaly

↓ in small stature

Antidiuretic

hormone

2.3–3.1 pg/mL ↑ in SIADH

↓ in diabetes insipidus

Urine specific

gravity

1.010–1.025 ↓ in diabetes insipidus

Adrenocorticotropic

hormone

120 pg/mL at 6–8 a.m. ↑ in Addison’s disease

↓ in Cushing’s syndrome, long-

term corticosteroid therapy

test Normal values significance Cortisol 5–25 g/100 mL ↑ in Cushing’s syndrome, stress

↓ in Addison’s disease, steroid

withdrawal

Vanillylmandelic

acid (VMA)

0.7–6.8 mg/24 h ↑ in pheochromocytoma

test Normal values significance Fasting plasma

glucose (FPG)

70–100 mg/dL in stress, Cushing’s syndrome

FPG 101–125 pre-diabetes

FPG 126 diabetes mellitus

↓ in hypoglycemia, Addison’s

disease

Oral glucose

tolerance test

Blood glucose less

than 140 mg/dL at 2

hours

BG 140–199 at 2 hours pre-

diabetes; BG 200 at 2 hours

diabetes mellitus

Glycosylated

hemoglobin

4%–7%

↑ in poor diabetes control

• A thyroid scan may be done to determine the presence of

tumors or nodules.

• A computed tomographic (CT) scan or magnetic resonance

imaging (MRI) may be done to locate a tumor or identify

hypertrophy of a gland.

• Ultrasound may be done of the thyroid or parathyroid glands to

determine if they are enlarged or to find masses.

• Biopsy is done to obtain tissue to examine for possible

cancerous cells.

NGRTCI Endocrine System Anatomy

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