Adrenal Cortex在线视频

Hello everyone!

We are going to discuss the structures

and functions of the adrenal cortex.

Firstly,

let us start with a case.

Rose was a 32-year-old woman

who developed systemic lupus

erythematosus (SLE).

The doctor said SLE was a kind of

autoimmune disease

and prescribed relatively

high dose methylprednisolone for 2 weeks.

After treatment,

Rose found the SLE symptoms have abated

but there were some unexpected changes

in her body,

including weight gain,

round face,

and acnes on the skin.

What was the function of

methylprednisolone in SLE?

Why did these unpleasant symptoms develop

after 14 days' therapy?

After going through the structures

and functions of the adrenal cortex,

you should be able to identify

the different zones in the cortex of

adrenal gland,

list the hormones produced by each zone;

and explain some symptoms

of the clinical disorders.

This picture shows us the location

of the adrenal glands,

just above the kidneys.

According to their location,

you can also call them suprarenal glands.

These glands are important

endocrine organs of the human body.

From a cross-sectional view,

the gland is divided into two parts,

the peripheral adrenal cortex

and the central medulla.

The two parts are different

in embryogenesis.

The cortex arises from mesoderm,

and the medulla from the neural crest

of the ectoderm.

Thus,

their structures and functions

are significantly different.

In this session,

we will focus on the cortex.

The adrenal cortex secretes

adrenocortical hormones

consisting of a mixture of

several types of sterols.

Cortical dysfunction,

no matter hyperadrenocorticism

or hypoadrenocorticism,

can cause clinical disorders

such as Cushing's syndrome

and Addison's syndrome, respectively.

Microscopically under low power field

we can easily see the cortical region,

the outer part of the gland,

with three concentric zones.

From outside to inside,

they are zona glomerulosa,

zona fasciculata, and zona reticularis.

Among these,

zona fasciculata occupies

most of the cortex.

At high power,

the zone details can be identified.

Let us start at the outermost zone.

The zona glomerulosa,

immediately beneath the capsule,

comprises about 15% of the cortex.

In this area,

round or columnar or pyramidal cells

are closely packed in spherical clusters.

Cells in this zone secrete

mineralocorticoid hormones

which can regulate the balance of

water and electrolytes,

sodium, and potassium,

through the kidney.

These hormones form part of

the Renin-Angiotensin-Aldosterone System

RAAS.

This pathway is involved in the regulation

of blood pressure through renal tubules

and collecting duct in water

and electrolytes absorption.

You can find the details

from physiology textbooks

or our school's online course of

"Clinical Physiology"

The second zone of adrenal cortex

is zona fasciculata.

This zone occupies about

65%-80% of the cortex

and consists of long cords

of large polyhedral cells.

These large cells

are filled with lipid droplets

and appear vacuolated

in routine histologic preparations.

These cells secrete glucocorticoids

and modulate the metabolism of

carbohydrate, fat, and proteins.

Production of glucocorticoids

is mainly regulated by

Adrenocorticotropic Hormone (ACTH),

which is secreted by pituitary gland.

The predominant glucocorticoid

in humans is cortisol.

For the physiological functions

of the glucocorticoids,

please again refer to

resources in physiology.

One of the functions of glucocorticoids

is in suppressing immune response

and inhibiting inflammation.

Exogenous glucocorticoids,

for example methylprednisolone,

are very useful

in treating autoimmune diseases

and other inflammatory disorders

such as asthma.

However,

prolonged use of high dose glucocorticoid

will lead to many side effects,

as manifested by Rose in our case.

The symptoms are similar to

the Cushing's syndrome

caused by increased ACTH

or an adrenal tumor.

The innermost zona reticularis

locates close to the medulla.

It occupies about 10% of the cortex,

and the cells are arranged in

a branching network.

The cells are smaller and

more heavily stained than other zones

because they contain

fewer lipid droplets

and more lipofuscin pigment.

These cells can secrete cortisol

and androgen

that supplement the sex steroids

secreted by the gonads.

Increased androgen secretion

during puberty by the testes

is required for the growth of

male accessory sex organs.

While in female,

small amount of androgen

promotes the growth of bone,

muscle, and body hair.

If the zona reticularis

secrets excess androgen in the female,

it may result in virilization,

including hirsutism,

gain in muscle mass,

breast atrophy, and amenorrhea etc.

Above we have discussed

the cortical region of adrenal gland.

Based on hormonal functions of the glands,

can you explain the symptoms Rose developed

after her prolonged high dose

methylprednisolone treatment?

Here are the references.

Thank you.

See you next time!