endocrine glands - doctor 2016 - ju medicine · 2018-08-11 · cell type present. their cytoplasm...

endocrine glands

Dr.shatarat

Dr.shatarat

Secretory cells of endocrine glands release their products,

signaling molecules called hormones, into the

neighboring vascularized compartment for uptake by

capillaries and distribution throughout the body.

▪ There is no

secretory duct as in exocrine glands

endocrine glands

Junqueira's

Basic Histology

Text and Atlas,

2014th Edition

Distribution by the circulation allows hormones to act on target cells with receptors for

those hormones at a distance from the site of their secretion.

Dr.shatarat

endocrine cells produce hormones

that act

on target cells only a short

distance awayThrough

1- local in interstitial fluid

2-short loops of blood vessels

For example :gastrin

made by pyloric G cells reaches

target cells in the fundic

glands

in which a signaling molecule

remains on the secreting cell’s surface

or adjacent extracellular

matrix and affects target cells when

the cells make contact.

Juxtacrine signaling is particularly

important in embryonic

and regenerative tissue interactions

contact-dependent signalling

Dr.shatarat

Why the CNS is not enough?

Why do we need Endocrine system?

Dr.shatarat

At puberty the female begins to

undergo regular monthly cycles called

THE OVARIAN CYCLE

Sexual cycles are under the control of the

(GnRH)

Controls the release of the Gonadotropin

FSH and LH

sexual cycles

The hypothalamus acts as a pulse generator which generates the pulsatile release of

Hypothalamus

Gonadotropin releasing hormone (GnRH)

from the anterior part of the pituitary gland

The follicle-stimulating hormone (FSH) luteinizing hormone (LH)

Control

The endometrial cycle ( menstrual cycle )

Controls

Brain

Dr.shatarat

Histology

Dr.shatarat

The HEMATOXYLIN stains nucleic acids

(plus calcium deposits and bacteria) blue.

Clear areas represent

water,

carbohydrate

lipid,

gas

The EOSIN stains most proteins

(actually, arginine and lysine) pink.

Dr.shatarat

Nuclei

Blue with the

will always stain

Hematoxylin.

will stain according to its composition.

The cytoplasm of cells

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Dr.shatarat

Cells of the adenohypophysisDr.shatarat

Pars distalis. This specimen of the pars distalis is

stained with brilliant crystal scarlet, aniline blue,

and Martius yellow to distinguish the various

cell types and connective tissue stroma. The

cords of cells are surrounded by a delicate

connective tissue stroma stained blue. The

sinusoidal capillaries are seen in close

association with the parenchyma and contain

erythrocytes stained yellow. In the region shown

here, the acidophils (Ac) are the most numerous

cell type present. Their cytoplasm stains cherry

red. The basophils (Bas) stain blue. The

chromophobes (Ch), although few in number in

this particular region, are virtually unstained.

640

Histology: A Text and Atlas: With Correlated Cell and Molecular Biology

The adenohypophysis is made of

epithelia cells !!!!!!!! and vascular

Sinusiods supported by a mesh of connective tissue

Most of the anterior lobe of the pituitary gland has

the typical organization of endocrine tissue

The cells are organized in clumps and cords separated

by

fenestrated sinusoidal capillaries of relatively large

diameter

Dr.shatarat

How many colors can be identified in this H&E section?????

Dr.shatarat

Adenohypophysis – high power

The adenohypophysis contains 3 cell types:-acidophils (stain red)-basophils (stain blue)-chromophobes (pale stain)

The adenohyphysis stains red-blue on low power because of the acidophils and basophils

Dr.shatarat

chromophils

(cells which take up

stain)

called acidophils and

basophils.

The anterior pituitary also contains one type of

chromophobe

(cells which stain only weakly)

Histologists identified three types of cells

according to their staining reaction, namely

Basophils (10%)

Acidophils (40%)

2- Chromophobes (50%)

1-Chromophils

Dr.shatarat

Parenchymal cells of the pars distalis to be

subdivided into acidophil cells (A), basophils

(B), and chromophobes (C) in which the

cytoplasm is poorly stained. Also shown are

capillaries and sinusoids (S)

stained with Gomori trichrome.

(X400

Dr.shatarat

Cells of the adenohypophysis

Chromophils

Acidophils Basophils

Chromophobes

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Importance of different colors?

• Acidophils secrete growth hormone and

prolactin

• Basophils secrete TSH, LH , FSH and ACTH

• Chromophobes are undifferentiated cells

Dr.shatarat

Cells of the Adenohypophysis

1- Chromophobes

• small weakly stained cells

• represent stem cells or (most likely)

• partially degranulatedchromophils

Dr.shatarat

The micrograph shows somatotrophs stained using an antibody

against somatotropin. (X400; Hematoxylin counterstain)

Subtypes of basophilic and

acidophilic cells are identified

by immunohistochemistry

Specific cells are usually named

according to their hormone’s

target cells

Acidophils secrete either growth

hormone (somatotropin) or

prolactin and are called

somatotrophs and lactotrophs

(or somatotropic cells and

lactotropic cells), respectively.

The basophilic cells are the

corticotrophs, gonadotrophs,

and thyrotrophs

Chromophils

Dr.shatarat

Chromophils

Acidophils

Somatotops Mammotrops

Basophils

Gonadotrops Thyrotrops Corticotrops

Dr.shatarat

1- Somatotrops:

• LM

• Form ~ 50% of the total number of chromophils.

• Occur in clumps and clusters

• Central nucleus

• EM

• Rod shaped mitochondria

• Many rER

• Many secretory granules (secrete GH)

• Moderate Golgi

• Action of GH: acts on growth of long bones via insulin-like growth factors synthesized in the liver.

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2- Mammotrops

• Form 15-20% of chromophils

• Occur singly

• Small polygonal cells

• Organelles are ill-defined

• During lactation organelles increase in size and number

• Secrete prolactin

• Action of prolactin: promotes milk secretion.

Dr.shatarat

3- Gonadotrophs

• Form ~ 10% of chromophils.

• Rounded cells.

• Prominent nucleus.

• Many granules with variable size.

• Cytoplasm contains well developed Golgi, many rER.

• Secrete FSH and LH.

• Action of FSH: promotes ovarian follicle development and estrogen secretion in women, and spermatogenesis in men.

• Action of LH: promotes follicular maturation and progesterone secretion in women and Leydig secretion in men.

Dr.shatarat

4- Thyrotrops

• Form ~ 5% of chromophils.

• Located away from sinusoids.

• Cytoplasm contains many small organelles.

• Secrete TSH.

• Action of TSH: stimulates thyroid hormone synthesis, storage, and liberation.

Dr.shatarat

5- Corticotrops

• Form 15-20% of chromophils.

• Round-ovoid cells scattered through pars distalis.

• Eccentric nucleus with few organelles.

• Secrete ACTH.

• Action of ACTH: stimulates secretion of adrenal cortex hormones and regulated lipid metabolism.

Dr.shatarat

• are characterized by a star like appearance with their cytoplasmic

processes encircling hormone-producing cells.

• They have the ability to make cell clusters or small follicles

• they do not produce hormones.

• Folliculostellate cells are interconnected by gap junctions.

• Based on immunocytochemical and electrophysiological studies, it

is hypothesized that the network of folliculo-stellate cells

interconnected by gap junctions transmits signals from the

pars tuberalis to pars distalis.

• These signals may regulate hormone release throughout the

anterior lobe of the pituitary gland. Thus, the folliculo-stellate

network may appear to function in addition to the hypophyseal portal

vein system

* Folliculostellate cells

Dr.shatarat

It is composed of neural tissue, containing

some 100,000 unmyelinated axons of large

secretory neurons with cell bodies in the

supraoptic and paraventricular nuclei of the

hypothalamus

Also present are highly branched glial

cells called pituicytes that resemble

astrocytes and are the most abundant

cell type in the posterior pituitary

Neurohypophysis (Posterior Pituitary)

Dr.shatarat

Neurohypophysis – high power

The neurohypophysis resembles neural tissue, with glial cells, nerve fibers, nerve endings, and intra-axonal neurosecretory

granules

Precursors of ADH (vasopressin) and oxytocin are synthesized in

the hypothalamus and transported to the pars nervosa where processing is completed

Dr.shatarat

Does not contain secretory cells.

Contains axons of secretory nerves; their mother cells are present in the paraventricular and supraoptichypothalamic nuclei.

Pituicytes are the most numerus cells.

Pituicytes resemble astrocytes.

Dr.shatarat

Neurohypophysis – high power

Hering bodies are large dilated axon terminal endings that are filled with accumulated neurosecretory granules

Dr.shatarat

Secretory neurons have larger diameter but are histologically and functionally similar to other neurons.

Axons of neurons transport ADH and oxytocin into the pars nervosa.

• Secretory products accumulate in the distal part of the axon in Hering bodies.

• Hering bodies appear slightly acidophilic.

• Secretory products are surrounded by a membrane and bound to neurophysin.

• Nerve impulses trigger the release release of peptides from neurosecretory bodies.

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Most Oxytocin is released from paraventricular nuclei.

Most ADH is released from supraoptic nuclei.

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ADH facilitates resorption of water from the distal tubules and collecting ducts of the kidney by altering the permeability of the cells to water.

Dr.shatarat

Oxytocin promotes contraction of smooth

muscles of the uterus and myoepithelial cells of the

breast.

Dr.shatarat

Tumours of the pituitary

may have two special features;

their endocrine disturbances and their relationship to the optic chiasma.

Chromophobe adenoma

is the commonest pituitary tumour.

As it enlarges it expands the

pituitary fossa (sella turcica) and

this may be demonstrated

radiologically. Compression of the

optic chiasma produces the very

rapid typical bitemporal

hemianopia.

The tumour itself is non-secretory

and gradually destroys the normally

functioning gland.

The patient develops

hypopituitarism with loss of sex

characteristics, hypothyroidism and

hypoadrenalism

Dr.shatarat

The eosinophil adenoma secretes the pituitary

growth hormones. If it occurs before puberty,

which is unusual, it produces gigantism; after

puberty it results in acromegaly.

The basophil adenoma is small, produces no

pressure effects and may be associated with

Cushing’s syndrome, although this more often

results from hyperplasia or tumour of the

suprarenal cortex.

Dr.shatarat

Gross anatomy

Dr. Shatarat & Dr. Badran

Glands drain ipsillaterally by superior, middle, and inferior thyroid veins.


In the fifth week, epithelium

of the dorsal wing

of the third pouch differentiates

into

INFERIOR PARATHYROID

GLANDwhile

the ventral wingforms

THE THYMUS

Both gland primordia lose

their connection with the

pharyngeal wall, and the thymus

then migrates in a caudal and a

medial

direction, pulling the inferior parathyroid

with it


Epithelium of the dorsal wing of the fourth pharyngeal pouch forms

When the

parathyroid gland

loses contact with the

wall of the pharynx,

it attaches itself to

the dorsal surface of

the caudally

migrating

thyroid as the

superior parathyroid

gland

Epithelium of the dorsal wing of

the fourth pharyngeal pouch

forms

THE SUPERIOR

PARATHYROID GLAND


Parathyroid Gland – low power

Low power of

parathyroid, showing

random cords of cells.

The parathyroid is

somewhat lobulated in

appearance and

considerable adipose

tissue is intermingled

with secretory portions.

Adipose tissue Cords of cells


Parathyroid Gland – high power

2 cells types of the Parathyroid:

Chief cells secrete parathormone (PTH). They have large round nuclei with a small amount of clear cytoplasm.

Oxyphil cells have smaller, darker nuclei and

relatively larger amount of cytoplasm. The

significance of the oxyphil cells is not clear.

Some

oxyphil cells show low levels of PTH

synthesis, suggesting that

these cells are transitional derivatives of

principal cells.

Chief

cells

Oxyphil cells


• Photomicrograph of human

parathyroid gland. This H&E–stained

specimen shows the gland with part

of its connective tissue capsule

(Cap). The blood vessels (BV) are

located in the connective tissue

septum between lobes of the gland.

The principal cells are arranged in

two masses (top and bottom) and are

separated by a large cluster of

oxyphil cells (center).

The oxyphil cells are the larger cell

type with prominent eosinophilic

cytoplasm. They may occur in small

groups or in larger masses, as seen

here. The principal cells are more

numerous. They are smaller, having

less cytoplasm, and consequently

exhibit closer proximity of their

nuclei. Adipose cells (AC) are

present in variable, although limited,

numbers

Rea

d o

nly


Also called pineal body, epiphysis

cerebri

is an endocrine or neuroendocrine

gland that regulates daily body

rhythm.

PINEAL GLAND

The pineal gland is a flattened, pine

cone–shaped structure

It measures 5 to 8 mm high and 3 to5

mm in diameter and weighs between

100 and 200 mg.

In humans, it is located at the

posterior wall of the third ventricle

near the center of the brain.

It develops from neuroectoderm of

the posterior portion of the roof of

the diencephalon and remains

attached to the brain by a short

stalk.


The pineal gland contains two types of parenchymal cells:

Pinealocytes

Interstitial (glial) cells.


The interstitial (glial) cells constitute

about 5% of the cells in the gland.

In addition to the two cell types,

the human pineal gland is characterized

by the presence of calcified concretions called

brain sandIt appears to be derived from precipitation of

calcium phosphates and carbonates on carrier

proteins that are released into the cytoplasm

when the pineal secretions are exocytosed


Melatonin▪ is released in the dark and regulates reproductive function in mammals by inhibiting

the steroidogenic activity of the gonads

▪ Production of gonadal steroids is decreased by the inhibitory action of melatonin on

neurosecretory neurons located in the hypothalamus (arcuate nucleus) that produce

GnRH.

▪ Inhibition of GnRH causes a decrease in the release of FSH and LH from the anterior

lobe of the pituitary gland. In addition to melatonin, extracts of pineal glands from

many animals contain numerous neurotransmitters, such as serotonin, norepinephrine,

dopamine, and histamine, and hypothalamic-regulating hormones, such as

somatostatin and TRH.

▪ Clinically, tumors that destroy the pineal gland are associated with precocious (early-

onset) puberty.

▪ Animal studies demonstrate that information relating to the length of daylight reaches

the pineal gland from photoreceptors in the retina.

▪ The pineal gland thus influences seasonal sexual activity. Recent studies in humans

suggest that the pineal gland has a role in adjusting to sudden changes in day length,

such as those experienced by travelers who suffer from jet lag.

▪ In addition, the pineal gland may play a role in altering emotional responses to the

reduced length of day during winter in temperate and subarctic zones known as

seasonal affective disorder (SAD)


Endocrine Pancreas

(Islets of Langerhans)


Endocrine Pancreas

Islets of Langerhans

Low power High power


Endocrine Pancreas

• Cells in the islets of Langerhans

– Alpha – secrete glucagon

– Beta – secrete insulin

– Delta – secrete somatostatin and gastrin

– PP – secrete pancreatic polypeptide


First described by Langerhans in 1869 (as an observation on the urine of pancreactictomized dogs).

In 1893 Gustave-Edouard Laguesse (1861-1927) attached the name Langerhans to the structures. Langerhans did not suggest any function for them. The book has been reprinted with an English translation by H. Morrison.


Spherical-oval cellular masses between the acini of the pancreas.

Variable in size and number of cells in them.

They form ~ 1 million secretroy units.

Not homogeneously distributed and increase in number towards the tail.

Surrounded by a very thin capsule.

They have the same embryological origin as the rest of the pancreas (endoderm).


Section of an adult human pancreas stained for glucagon (green) and insulin (red)


In H & E cells show variation in staining reaction between acidophilia and basophilia.

E.M. shows typical poly peptide secreting cells with variable amount of granules.

Immunohistochemistry is the only accurate method to differentiate between cells.


Major pancreatic cells cell

Cell Location % Secretion Function

α Peripheral ~ 20 Glucagon ↑ Blood glucose level; ↑ glycogenolysis and lipolysis

β Central ~ 70 Insulin ↓ Blood glucose level

δ Scattered 5-10 Somatostatin Inhibits release of other cells

F (PP) Scattered <1 Pancreatic polypeptide

↑ activity of chief cells, ↓ bile secretion.↓ pancreatic enzyme and HCO3 secretion.↓ intestinal motility


Suprarenal (adrenal) Glands


Adrenal Histology


The gland is divided into an outer cortex and an inner medulla.

The adrenal cortex is composed of three zones histologically:

• Outer zona glomerulosa, site for aldosterone synthesis.

• Central zona fasciculata produce cortisol, and

• Inner zona reticularis produce androgens.


Zona glomerulosa

Is the exclusive site of production of aldosterone.

Consists ~ 15% of the cortex.

Cells are arranged in closely packed clusters continuous with the next layer.

Cells are small pyramidal-columnar with spherical nuclei.

Clusters of cells are surrounded by fenestrated sinusoidal capillaries.

Cells have abundant sER, large mitochondria with shelf-like cristae, Golgi complex, few rER, and few lipid droplets.


Zona glomerulosa secretes mineralocorticoids, that function in the regulation of sodium and potassium homeostasis and water balance.

The main mineralocorticoid is aldosterone.

Aldosterone stimulates resorption of sodium from:

• Distal renal tubules.

• Gastric mucosa.

• Salivary glands.

• Sweat glands.

The zona glomerulosa is under the feed back control of the renin-angiotensin-aldosterone system.


Zona Glomerulosa


Zona Fasciculata

The thickest middle zone that form ~80% of the cortex.

Cells are large polyhedral, arranged in long straight cords 1-2 cells thick.

Cords are separated by sinusoidal capillaries.

Cells are lightly stained, commonly binucleated.

Cells are typical steroid synthesizing cells.

Cytoplasm contains lipid droplets.

Cells secrete glucocorticoids, mainly cortisol.


Glucocorticoids may have different, even opposite effects in different tissues:

• In the liver:

• ↑ conversion of aminoacids to glucose.

• ↑ polymerization of glucose to glycogen.

• ↑ uptake of aminoacids and fatty acids.

• In adipose tissue: ↑ breakdown of lipids to glycerol and free fatty acids.

• In other tissues: ↓ rate of glucose use and ↑ oxidation of fatty acids.

• In cells: ↓ protein synthesis and ↑ protein catabolism.


Zona reticularis

The inner zone, forms 5-7% of the cortex. Contains light and dark cells.

Cells are smaller than the reticularis, their nuclei are more deeply stained.

Cells are arranged in anastomosing cords separated by fenestrated capillaries.

Cells have few lipid droplets.

Cells are typical steroid-secreting cells.

Their principal secretion is weak androgen (minimal glucocorticoids).


Adrenal medulla

Composed of large, pale staining epithelioid cells; chromaffin cells, connective tissue, sinusoidal capillaries and nerves.

The chromaffin cells are modified neurons.

Myelinated, presynaptic nerves pass directly to chromaffin cells.


E.M shows that there are two types of chromaffin cells:

• Cells containing large dense core vesicles → secrete norepinephrine.

• Cells containing small homogeneous less dense vesicles → secrete epinephrine.

Chromaffin cells


Glucocorticoids secreted in the cortex induce the conversion of norepinephrineto epinephrine in chromaffin cells.

Most of chromaffin cells at the cortico-medullary junction secrete epinephrine.

Norepinephrine-secreting cells are also found in paraganglia (collections of catecholamine-secreting cells adjacent to the autonomic ganglia) and in various

viscera. The conversion of norepinephrine to epinephrine (adrenalin) occurs only in chromaffin cells of the adrenal medulla

About 80% of the catecholamine secreted from the adrenal

is epinephrineDr. Shatarat & Dr. Badran

The catecholamines, in concert with the glucocorticoids, prepare the body for the “fight-or-flight” response.

Sudden release of catecholaminesestablishes conditions for maximum use of energy.


are innervated by preganglionic sympathetic neurons,

They trigger epinephrine and norepinephrine release

during stress and intense emotional reactions.

Epinephrine increases:

▪ heart rate

▪ dilates bronchioles,

▪ dilates arteries of cardiac and skeletal muscle.

Norepinephrine constricts:

▪ vessels of the digestive system and skin, increasing

blood flow to the heart, muscles, and brain.

Both hormones stimulate glycogen breakdown, elevating blood glucose levels.

Together these effects augment the capability for defensive reactions or escape of

stressors, the fight-or-flight response.

During normal activity the adrenal medulla

continuously secretes small quantities of these

hormones.

Medullary chromaffin cells


Thyroid gland


Thyroid follicle:

• The structural and functional unit of the thyroid gland.

• Consists of a group of cells resting on the same basal lamina surrounding a lumen filled with colloid.

• The follicles are variable in size.

• Hormones are stored in the follicles.

• Each follicle is surrounded by variable amount of connective tissue.


Follicular cells (principal cells):

• Squamous-columnar cells according to activity.

• Basophilic cytoplasm.

• Nucleus: round-ovoid with 2 nucleoli.

• Many rER.

• Numerous apical lysosomes and mitochondria.

• Supranuclear Golgi complex.

• Apical microvilli.

• Numerous vesicles in the cytoplasm.


Parafollicular cells (Clear cells, C cells):

• Pale staining, larger than follicular cells.

• Occur singly or in clusters among follicular cells.

• Overlapped by follicular cells.

• E.M:

• Moderate rER.

• Well-developed Golgi.

• small, dense, basal secretory granules.

• Secrete calcitonin:

• Inhibits bone resorption by osteoclasts.

• Stimulated when Ca2 is high.


C

C

C


Thyroid gland

1. Recognize and understand the coverings of the thyroid gland and their clinical

importance.

2. Recognize and understand the main parts of the thyroid gland and their locations,

relations and connections.

3. Comprehend the blood supply of the thyroid gland, their relations with recurrent and

external laryngeal nerves.

4. Understand the embryological origins of the pituitary gland and its associated

malformations.

5. Grasp the clinical correlations of the midline structures of neck related to the thyroid

gland and differentiate between them and the those on the lateral side of the neck.

6. Recognize and understand imaging of the thyroid gland.

7. Grasp the histological structure of the thyroid gland and its cells under light.

7/14/2018 Dr.Shatarat

Gross anatomy


Transverse sections through the neck at the

level of the second sixth cervical vertebrae

➢ It is placed anteriorly

in the lower neck

at the level with

the 5th cervical to the

1st thoracic vertebrae


It consists of

Right and left lobes connected

by

a narrow isthmus 7/14/2018 Dr.Shatarat

its apex being directed upward as far as

the oblique line on the lamina of the

thyroid cartilage

3- Lobs

its base

lies below at the level of the fourth or

5th tracheal ring.

Each lobe is pear shaped

Apex

base

The posteromedial aspects of the lobes are

attached to the side of the cricoid cartilage by a

lateral thyroid ligament

Note

It should be noted that the normal thyroid gland is nearly

always asymmetric. The right lobe may be even twice as

large as the left lobe.

The right upper pole extends higher up in the

neck, and the lower pole extends lower.


4- THE ISTHMUS

is often present, and it projects

upward from the isthmus

5- Pyramidal lobe

The isthmus extends

across the midline in

front of

the 2ed, 3ed , and 4th

tracheal rings

A fibrous or fibromuscular band, the levator of the thyroid gland, musculus levator glandulae

thyroideae, sometimes descends from the body of the hyoid to the isthmus or pyramidal lobe

Note

persists in at least 15% of

the population


True capsule

False capsule

6- Coverings and fascia of the thyroid gland

The thyroid gland is surrounded by


A-True capsule, a thin fibrous

capsule,

which is formed by condensation of

the stroma of the gland.

➢ It is attached by means of dense

connective tissue to the cricoid

cartilage (part of the larynx) and

superior tracheal rings (part of the

trachea).

The True capsule of thyroid capsule is

much denser in front than behind and the

enlarging gland therefore tends

to push backwards, burying itself round the

sides and even the back of the

trachea and oesophagus.

Clinical note

cause dangerous DyspneaDysphagia7/14/2018 Dr.Shatarat

B- False capsuleit is a loose sheath formed by the visceral

portion of the pretracheal layer of deep

cervical fascia external to the true capsule

➢ The false capsule thickens between the

cricoid cartilage and thyroid gland to

form the

ligament of Berry(The suspensory ligament of the thyroid)

gland

(attaches the thyroid gland to trachea)


The false capsule of the thyroid

gland also

attaches the gland to

the larynx and even to the hyoid

bone

This explains why the thyroid gland

follows the movements of the

larynx in swallowing.

This information is important because any pathologic neck

swelling that is part of the

thyroid gland will move upward when the patient is asked

to swallow

It is clear that the false

capsule is attached to

Both the larynx and

trachea

Clinical note


a large goitre will extend downwards into the

superior

mediastinum

(‘Plunging Goitre’)

The pretracheal layer of deep cervical fascia is attached to hyoid bone

Retrosternal Goiter

The attachment of the sternothyroid muscles to the thyroid

cartilage effectively binds down the thyroid gland to the larynx

This limits upward expansion of the gland

However, downward expansion has no limitation

And

Or


7- Relations of the Lobes

C-The

sternothyroi

d

B-The

sternohyoid

D-The anterior

border of the

sternocleidomastoid

A-The

superior belly

of the

omohyoid


The anastomosis between

the superior and inferior thyroid arteries.

Posterior view


Posterolaterally:

The carotid sheath with the

common carotid artery, the

internal jugular vein, and the

vagus nerve

The larynx, the trachea, the pharynx,

and the esophagus. Associated with

these structures are the cricothyroid

muscle and its nerve supply, the

external laryngeal nerve. In the

groove between the esophagus and

the trachea is

the recurrent

laryngeal nerve

Medially:


A-The superior thyroid artery

B-The inferior thyroid artery

C- Sometimes the thyroidea ima.

A-The superior thyroid artery, a branch of

the external carotid artery, descends to the

upper pole of each lobe, accompanied by

The External Laryngeal

Nerve


The superior thyroid artery on each side is related

to the external laryngeal nerve, which supplies the

cricothyroid muscle.

Damage to the

external

laryngeal

nerve

results in an

inability to

tense the

vocal folds

and in

hoarseness

Thus, The Superior Thyroid Artery during surgery on the thyroid ,

is ligated near the gland to avoid injury to

the external laryngeal nerve 7/14/2018 Dr.Shatarat

➢ a branch of the thyrocervical trunk,

ascends behind the gland to the level of

the cricoid cartilage.

➢ It then turns medially and downward to

reach the posterior border of the gland.

The recurrent laryngeal

nerve crosses either in front of or behind the artery,

or it may pass between its branches.

B-The inferior thyroid artery


The terminal branches of the

inferior

thyroid artery

on each side are related to the

RECURRENT LARYNGEAL

NERVE.


Thus, THE INFERIOR THYROID ARTERY during

surgery on the thyroid ,

is ligated away from the gland to avoid injury to

the recurrent laryngeal nerve


C-The thyroidea ima, In

approximately 10% of people, a

thyroid ima artery

ascends on the anterior surface of

the trachea, which it supplies,

and continues to the isthmus of

the thyroid gland.

The possible presence of this artery

must be considered when performing

procedures in the midline of the neck

inferior to the isthmus because it is a

potential source of bleeding

arises from the brachiocephalic trunk,

or the arch of the aorta,

from the right common carotid

subclavian, or internal thoracic arteriesVari

ab

le

Clinical note


Lesions of the Laryngeal Nerves

The muscles of the larynx are innervated by

the recurrent laryngeal nerves, with the

exception of the cricothyroid muscle, which is

supplied by the external laryngeal nerve. Both

these nerves are vulnerable during operations

on the thyroid gland because of the close

relationship between them and the arteries

of the gland.

To be discussed next year


9-The veins from the thyroid gland

C-The inferior thyroid vein

The inferior thyroid veins of the two

sides anastomose with one another as

they descend in front of the trachea.

They drain into the left brachiocephalic

vein in the thorax

A-Superior thyroid vein

which drains into the internal jugular vein;

B-The middle thyroid vein

which drains into the internal jugular vein;


10-The lymphatic vessels of the thyroid gland

communicate with a capsular network of

lymphatic vessels

From this network, the vessels pass

initially to prelaryngeal, pretracheal,

and paratracheal lymph nodes, which

drain in turn to the superior and

inferior deep cervical nodes

Inferior to the thyroid gland, the

lymphatic vessels pass directly to the

inferior deep cervical lymph nodes


The uppermost, just above the

thyroid

isthmus, in front of the cricoid

cartilage, and medial to

a pyramidal lobe, if present, is a

constant node group

of one to five nodes, which has

been termed

The Delphian node

enlargement of which is

indicative of metastasis

from thyroid or

laryngeal carcinoma.


with development of the arches and clefts,

a number of outpocketings,

The pharyngeal

pouches appear

THE PHARYNGEAL ARCHES

are separated

by deep clefts known as

PHARYNGEAL

CLEFTS

In a cross section of the embryo in the area of the head and neck

The following can be noticed

THE PHARYNGEAL ARCHES


Pharynx (ventral view) 4th week

Thyroid Gland

1-begins to develop during the

third week as an endodermal

thickening in the floor of the

pharynx

between the tuberculum

impar and the copula at a

point later indicated

by the foramen cecum


2- It descends in front of the pharyngeal gut as a bilobed diverticulum

3- During this migration, the thyroid

remains connected to the tongue by a

narrow

canal, the thyroglossal duct.


4-As development continues, the duct elongates, and its distal end becomes bilobed. Soon,

the duct becomes a solid cord of cells, and as a result of epithelial proliferation, the bilobed

terminal swellings expand to form the thyroid gland

5-The thyroid gland now migrates inferiorly in the neck and passes either anterior to, posterior to,

or through the developing body of the hyoid bone.

6-By the seventh week, it reaches its final position in relation to the larynx and trachea.

Meanwhile, the solid cord connecting the thyroid gland to the tongue fragments and

disappears. 7/14/2018 Dr.Shatarat

7-The site of origin of the thyroglossal duct on

the tongue remains as a pit called

the foramen cecum.

8-The thyroid gland may now be

divided into a small median isthmus

and two large lateral lobes

Pharynx and derivatives (between 6th and 7th weeks)7/14/2018 Dr.Shatarat

9-The ultimobranchial bodies (from the fifth pharyngeal pouch) and

neural crest cells are believed to be incorporated into the thyroid gland,

where they form the parafollicular cells, which produce

calcitonin.

Second origin of the thyroid gland

as we mentioned before, most glands have two different origins


Congenital Anomalies of the

Thyroid Gland

1-Agenesis of the Thyroid

Failure of development of the thyroid gland may occur and

is the commonest cause of cretinism

2-Incomplete Descent of the Thyroid

The descent of the thyroid may be arrested at

any point

between the base of the tongue and the trachea

Lingual thyroid is the most common form of

incomplete

descent The mass of tissue


Aberrant thyroid tissue may be found anywhere along the path of

descent

of the thyroid gland. It is commonly found in the base of the tongue,

just behind the foramen cecum, and is subject to the same diseases

as the

thyroid gland itself.

caution!!!

A mass in the

posterior midline

might be the only

thyroid in the

patient’s body


Th

yro

glo

ss

al

Du

ct

an

d T

hyro

id A

bn

orm

ali

ties


3-Persistent Thyroglossal Duct

Conditions related to a persistence of

the thyroglossal duct

usually appear in childhood, in

adolescence, or in young

adulthood


Thyroglossal Duct and Thyroid

Abnormalities

A thyroglossal cyst may lie at any

point along the migratory pathway

of the

thyroid gland but is always near or in

the midline of the neckby its name, it is a cystic remnant of

the thyroglossal duct, Although

approximately

50% of these cysts are close to or

just inferior to the body of the hyoid

bone they may also be found at the

base of the tongue

or close to the thyroid cartilage.

Sometimes a thyroglossal cyst is

connected to

the outside by a fistulous canal, a

thyroglossal fistula. Such a fistula

usually

arises secondarily after rupture of a

cyst but may be present at birth.7/14/2018 Dr.Shatarat

Thyroglossal cyst.

These cysts, which

are remnants of the

thyroglossal

duct, may be

anywhere along the

migration pathway of

the thyroid gland.

They are commonly

found behind the

arch of the hyoid

bone. An important

diagnostic

characteristic

is their

midline

location.7/14/2018 Dr.Shatarat

Branchial fistulas occur when the

second pharyngeal arch fails to grow

caudally

over the third and fourth arches, leaving

remnants of the second, third,

and fourth clefts in contact with the

surface by a narrow canal.

Such a fistula, found on the lateral

aspect of the neck directly anterior to

the sternocleidomastoid muscle,

usually provides drainage for a

lateral cervical

cyst These cysts, remnants of the

cervical sinus, are most often

just below the angle of the jaw

Branchial Fistulas

Frequently a lateral cervical cyst is not

visible at birth but becomes evident as it

enlarges during childhood.

Patient with a lateral cervical cyst. These cysts are always on the lateralside of the neck in front of the sternocleidomastoid muscle. They commonly lie under

the angle of the mandible and do not enlarge until later in life.7/14/2018 Dr.Shatarat

4-Thyroglossal Sinus (Fistula)

Occasionally, a thyroglossal cyst ruptures

spontaneously,

producing a sinus). Usually, this is a result of

an infection of a cyst. All remnants of the

thyroglossal

duct should be removed surgically


1-As the lateral lingual swellings increase in size, they overgrow the

tuberculum

impar and merge, forming the anterior two-thirds, or body, of the tongue

Since the mucosa covering the body of the tongue originates

from the first pharyngeal arch, sensory innervation to this area is by

the mandibular branch of the trigeminal nerve.

The body of the tongue is

separated from the posterior third by a V-shaped groove,

the terminal sulcus

2-The posterior part, or root, of the tongue originates from the second,

third,

and part of the fourth pharyngeal archThe fact that sensory innervation to

this part of the tongue is supplied by the glossopharyngeal nerve

indicates that

tissue of the third arch overgrows that of the second.

Some of the tongue muscles probably differentiate in situ, but most are

derived from myoblasts originating in occipital somites.

Thus, tongue musculature

is innervated by the hypoglossal nerve.7/14/2018 Dr.Shatarat

Tuberculum impar

Copula

(hypobranchial

eminence

Epiglottal

swelling

Palatine

tonsil

Root of

tongue

Foramen

cecum

in t

he f

loo

r o

f th

e p

hary

nx


Metastatic disease to the thyroid is common; it

likely

relates to its rich blood supply of approximately

560 mL/100 g tissue/min (a flow rate per gram

of tissue

that is second only to the adrenal glands)


endocrine glands - doctor 2016 - ju medicine · 2018-08-11 · cell type present. their cytoplasm...

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