Cui Dongmei. Atlas of Histology: with functional and clinical correlations. 1st ed

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CHAPTER 17

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335

Blood

vessel

Blood

vessel

Septa

Blood

vessels

Blood

vessels

Capsule

Parathyroid Glands

Figure 17-9A. Overview of the parathyroid glands. H&E, 37

The four small parathyroid glands typically lie on the posterior

surface of the thyroid gland (Fig. 17-1) and are separated from

the thyroid gland by a connective tissue capsule. Connective tissue

septa with blood vessels divide each parathyroid gland into many

incomplete lobules. The parathyroid glands are derived from the

endoderm of pharyngeal pouch 3 (the inferior parathyroid glands)

and pouch 4 (the superior parathyroid glands). There are two

types of cells in the parathyroid glands: chief cells and oxyphil

cells (Fig. 17-9B). Adipocytes are commonly found in the parathy-

roid glands in older individuals.

Oxyphil cells

Capillary

Connective

tissue

septum

Connective

tissue

septum

Blood

vessels

Blood

vessels

Oxyphil

cells

Oxyphil

cells

Chief

cells

Chief

cells

Chief

cells

Chief

cells

Figure 17-9B. Chief cells and oxyphil cells of the parathyroid

glands. H&E, 139; inset 296

The chief cells are smaller and more numerous than the oxyphil cells.

They are distributed throughout the glands and are the principal cells

in the parathyroid glands. Each chief cell has a large round nucleus

with a small amount of clear cytoplasm. These chief cells produce

PTH, also called parathormone, which is secreted in response to

low blood calcium levels. PTH indirectly promotes osteoclast pro-

liferation and increases their activity of absorption of bone tissue to

increase blood calcium levels. The oxyphil cells are large cells with

acidophilic (pink) cytoplasm as shown here. Each cell has a small

nucleus and a large amount of cytoplasm containing numerous mito-

chondria. The oxyphil cells are often arranged in clusters; individual

cells can also be found scattered among the chief cells. The oxyphil

cells appear at puberty, and their numbers increase with age. Their

functions are unclear.

CLINICAL CORRELATION

Figure 17-9C.

Parathyroid Adenoma. H&E, 96

Parathyroid adenomas are benign neoplasms of the parathyroid

gland representing the most common cause of primary hyperpara-

thyroidism, in which autonomous overproduction of parathyroid

hormone occurs. The increased parathyroid hormone results in

elevated blood calcium (hypercalcemia), which may cause constipa-

tion, kidney stones, neuropsychiatric issues, and bone diseases such

as osteitis ﬁ brosa cystica. The majority of cases are asymptomatic,

discovered incidentally when hypercalcemia is detected on routine

blood tests. Most cases are sporadic, but some cases may be related

to inherited conditions like multiple endocrine neoplasia (MEN1

and MEN2). Parathyroid adenomas are usually solitary, whereas

parathyroid hyperplasia tends to affect all four glands. Grossly, these

adenomas are well circumscribed with a red-to-brown cut surface.

Histologically, an adenoma is enveloped with a capsule, is usually

composed of monomorphic chief cells, and tends to compress the

surrounding normal parathyroid tissue. Deﬁ nitive treatment is surgi-

cal removal of the parathyroid gland containing the adenoma.

Adenoma

composed

of chief cells

Normal

parathyroid

gland with

adipose tissue

Adipocytes

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Organ Systems

Zona reticularis

Zona fasciculata

Zona glomerulosa

Capsule

Cortex

Medulla

Cortex

Medulla

Fig. 17-10B

Zones of the adrenal gland

Zona reticularis

Medulla

Zona reticularis

Zona fasciculata

Zona glomerulosa

Capsule

Capillary

Capillaries

Cortex

Figure 17-10A. Overview of the adrenal glands. H&E, 7

An adrenal gland covers the apical region of each kidney. It is

also called the suprarenal gland (Fig. 17-1A). Each adrenal gland

is covered by a connective tissue capsule and has a cortex and a

medulla. The cortex of the adrenal gland is derived from the meso-

derm and can be divided into three zones: the zona glomerulosa,

zona fasciculata, and zona reticularis. Hormone-producing cells

in the cortex secrete several types of hormones: mineralocor-

ticoids, glucocorticoids, and weak androgens. The medulla of

the adrenal gland is derived from the neural crest and contains

cell bodies of sympathetic ganglion neurons and their axons as

well as chromafﬁ n cells, which synthesize and release adrenaline

(epinephrine) and noradrenaline (norepinephrine) (Fig. 17-12A,B).

Figure 17-10B. Cortex of the adrenal gland. H&E, left 41, left (insets) 466; right (4 panels) 163

The cortex of the adrenal gland contains many glandular cells. These cells are arranged in cords, which are formed by hormone secretory

cells. The capillaries run parallel to these cords. (1) The zona glomerulosa lies beneath the connective capsule and consists of secretory cells

that contain lipid droplets (vacuoles) and a pale-staining cytoplasm. These cells are arranged in round or ovoid clusters (like glomeruli);

they secrete mineralocorticoids, mainly aldosterone, which control the electrolyte balance by acting on the distal tubules of the kidney to

increase Na

and decrease K

absorption. (2) The zona fasciculata contains hormone-secreting cells that secrete glucocorticoids (mainly

cortisol and corticosterone). The glucocorticoids stimulate glycogen synthesis in the liver; increase carbohydrate, fat, and protein metabo-

lism; and suppress the immune response by slowing down immune cell (lymphocyte) circulation. ACTH stimulates the production of glu-

cocorticoids. The cells in the zona fasciculata contain many lipid droplets, which make the cytoplasm appear light and vacuolated. These

cells are arranged in long cords in which cell nuclei are packed close to one another with their pale-stained cytoplasm facing the capillaries.

(3) The zona reticularis is adjacent to the medulla. Its secretory cells contain only a few lipid droplets, and their cytoplasm is stained dark

and acidophilic in appearance. The cells are arranged in anastomosing cords, which are intermixed with by surrounding capillaries. These

secretory cells secrete androgens (mainly dehydroepiandrosterone), which can be converted into testosterone or estrogen. ACTH also

stimulates the secretion of the adrenal androgens. (4) The junction between the zona reticularis and the medulla is shown here. There are

many blood vessels separating the zona reticularis of the cortex and the medulla. The cells in the medulla are stained lighter than the cells

in the zona reticularis. The left insets show a high power view of hormone secreting cells in the zona glomerulosa, zona fasciculata, and

zona reticularis of the adrenal gland cortex. The right panels show regions of the adrenal gland that are indicated by the dashed boxes.

Adrenal Glands (Suprarenal Glands)

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337

Secretory cells in

zona reticularis

Lipid droplets

Rough

endoplasmic reticulum

Smooth

endoplasmic reticulum

Nucleolus

Mitochondrion with

tubular cristae

Figure 17-11A. Adrenal cortical cells, adrenal cortex. EM, 11,500; inset (color) H&E, 680

Cells of the adrenal cortex have features common to all cells that synthesize and secrete steroid hormones. The three most prominent

components of the cytoplasm are an abundance of smooth endoplasmic reticulum (SER), mitochondria that have peculiar tubular cris-

tae, and lipid droplets. Cholesterol, the precursor of steroid hormones, is stored as esters in the lipid droplets. Enzymes necessary for

synthesis of steroid hormones are located in the SER and in the inner mitochondrial membrane, so hormone production is a cooperative

function of these two organelles. Although proteins are not secreted by these cells, protein synthesis is required to maintain structure

and function. This is reﬂ ected by the prominent nucleolus and by the patches of RER.

CLINICAL CORRELATION

Figure 17-11B.

Pheochromocytoma. H&E, ×96

Pheochromocytomas are neoplasms of the adrenal medulla

characterized by the production of catecholamines, such as

epinephrine and norepinephrine, which cause signiﬁ cant

hyper-

tension, often episodic, in affected patients. Most pheochro-

mocytomas are sporadic, but about 10% are associated with

familial syndromes such as MEN (types 2A and 2B), and von

Hippel-Lindau. Some pheochromocytomas are bilateral, and

although most occur in adults, about 10% occur in children.

Grossly, most of these tumors are well circumscribed and

range in size from a few grams to kilograms. Microscopically,

pheochromocytomas can have a diverse appearance, from

spindle cells to large, bizarre cells. The cells are often arranged

in nests, or cell packets called zellballen. Histologic features

alone do not reliably separate benign tumors from malignant

ones; therefore, the demonstration of metastases is necessary to

ascertain malignancy. Deﬁ nitive treatment is surgical removal

of the tumor.

Pheochromocytoma

with zellballen

Adjacent normal

adrenal cortex

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UNIT 3

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Organ Systems

Cell bodies of

ganglion neurons

Cell bodies of

ganglion neurons

Nerve fibers

Chromaffin

cells

Chromaffin

cells

Blood cells

in the vein

Blood cells

in the vein

Nucleus of chromaffin cell

Nucleolus

Rough

endoplasmic reticulum

Norepinephrine

granule

Norepinephrine

granule

Lumen of

fenestrated

fenestra

ted

capillary

Lumen of

fenestrated

capillary

Chromaffin cells

Figure 17-12A. Adrenal medulla. H&E, 140; inset (left)

340; inset (right) 158

The adrenal medulla is derived from the neural crest; its embry-

onic origin is different from that of the adrenal cortex. The cells

in the adrenal medulla include chromafﬁ n cells and ganglion neu-

rons. Large blood vessels (veins) are found in the medulla; these

vessels drain blood out of the adrenal gland. Chromafﬁ n cells are

irregularly shaped neuroendocrine cells and are the predominant

cells in the adrenal medulla. These cells have round nuclei with

pale-staining cytoplasm as shown here. They have numerous

plasma secretory granules that stain intensively with chromium

salts; therefore, they are called chromafﬁ n cells. These cells secrete

the sympathomimetic hormones adrenaline (epinephrine) and

noradrenaline (norepinephrine) in response to stress. The sympa-

thetic ganglion neurons have large cell bodies that are surrounded

by supporting cells as shown in the left inset. The adrenal medulla

is innervated by sympathetic preganglionic nerves.

Figure 17-12B. Cells of the adrenal medulla. EM, 5,700; inset (color) H&E, 1,632

Cells of the adrenal medulla synthesize and secrete adrenaline (epinephrine) and noradrenaline (norepinephrine), with adrenaline

being the main product. These catecholamines are both synthesized from the amino acid tyrosine through a series of reactions that

occur in the cytosol and within the granules in the cytoplasm. The generation of the granules, along with the enzymes, packag-

ing proteins, and membrane proteins, involves the RER and Golgi complex, so these cells have equipment similar to a protein-

synthesizing cell, although their product is not a protein. The granules vary greatly in size and appearance, a reﬂ ection partly of the

current state of activity (synthesis, storage) and partly of the catecholamine (epinephrine, norepinephrine) stored in the granule. The

granules that store norepinephrine (noradrenaline) are the large electron-lucent proﬁ les containing a small electron-dense particle at

the edge of the cavity. Like the cells of the cortex, the cells of the adrenal medulla are closely associated with the walls of fenestrated

capillaries. However, the edge of the vessel in the upper left corner of this view does not show the fenestrations.

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339

Superior

colliculus

Posterior

commissure

Pineal

gland

Capsule

Septum

Brain

sand

Brain sand

Pinealocytes

Capillary

Neuroglial

cells

Neuroglial

cells

Brain

sand

Brain

sand

Neuroglial

cells

Neuroglial

cells

Pineal Gland

Figure 17-13A. Overview of the pineal gland. H&E, 5

The pineal gland is a pinecone-shaped neuroendocrine gland about 8 mm

in length that produces melatonin and is covered by a capsule of pia mater.

The pineal gland is part of the epithalamus (a diencephalic structure) that

extends caudally from its attachment immediately superior to the poste-

rior commissure into the superior (quadrigeminal) cistern. It is superior

to the colliculi of the midbrain. Secretion of melatonin is stimulated by

darkness and inhibited by light. The level of this hormone increases dur-

ing sleep. Connective septa divide the pineal into poorly deﬁ ned lobules.

This gland contains pinealocytes, neuroglial cells, and blood vessels.

Calciﬁ ed concretions called brain sand (also called corpora arenacea)

may also be present in the pineal gland, especially in older patients.

Figure 17-13B. Pinealocytes and brain sand of the pineal gland.

H&E, 140; insets 363

The pineal gland is composed of two types of cells: pinealocytes and

neuroglial cells. The pinealocytes are modiﬁ ed neurons, which have

round or ovoid nuclei with pale-stained cytoplasm containing granules

ﬁ lled with melatonin. The pinealocytes synthesize melatonin, which is

important in the regulation of the circadian rhythms (day and night

cycles). The pinealocytes are larger than the neuroglial cells and have

a long cytoplasmic process that extends to the capillaries; their secre-

tory granules are released into the capillaries. The neuroglial cells are

supportive cells with small, dark nuclei. They are also called pineal

astrocytes and are commonly found near the capillaries. The particles

of brain sand assume various sizes as shown here; their function is not

known. Other functions of the pineal gland may relate to promoting

sleep and sexual development; enhancing mood and slowing the aging

process; and, possibly, inhibiting the growth of some tumors.

The calciﬁ cations (brain sand) within the pineal gland increase with

age. These calciﬁ cations appear white in computed tomography

scan and magnetic resonance imaging and are commonly used as a

natural landmark by radiologists and neurologists.

CLINICAL CORRELATION

Figure 17-13C.

Pineoblastoma. Immunohistochemical preparation

for

synaptophysin, 198

Pineoblastoma is an aggressive malignant tumor in children, which

arises in the pineal gland. Because it commonly consists of cellular

sheets that lack an architectural pattern, it is described as a small blue

cell tumor. The term embryonal is also used to emphasize the rudi-

mentary developmental stage of the tumor, although in some tumors

the cells begin to show differentiation into neurons, or glial cells, or

even rods and cones. The earliest stages of such specialization may

be detectable before any architectural alteration. Synaptophysin is a

protein associated with synapses. An antibody to this marker protein,

conjugated to the enzyme peroxidase, creates a colored metabolite

wherever synaptophysin appears in cell cytoplasm or membranes. In

the image on the left, a brown compound marks the tumor cells that

contain synaptophysin. Tumor treatments can be individually formu-

lated based on the different cellular components.

Tumor

Nucleus of

tumor cell

Synaptophysin in

tumor cell cytoplasm

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UNIT 3

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Organ Systems

Islets of

Langerhans

Islets of

Langerhans

Exocrine

secretory cells

Exocrine

secretory cells

Small

artery

Small

artery

Septum

Interlobular

duct

Interlobular

duct

Connective

tissue

Connective

tissue

Islet of

Langerhans

Islet of

Langerhans

Exocrine

secretory cells

Endocrine

secretory cells

Exocrine

gland

Exocrine

gland

Exocrine

gland

Exocrine

gland

Capillaries

Islet of

Langerhans

Endocrine Pancreas

Figure 17-14A. Islets of Langerhans, endocrine pancreas. H&E,

39

The pancreas has endocrine and exocrine components. The endocrine

component consists of the islets of Langerhans, which are clusters of

endocrine cells within a capillary network. There are numerous pale-

staining islets of Langerhans scattered throughout the pancreas, and

each of them is surrounded by an eosinophilic exocrine component

of the pancreas as shown here. A connective tissue septum divides

the pancreas into lobules. Two interlobular ducts, surrounded by the

connective tissue, belong to the exocrine pancreas, from which they

carry secretions. The endocrine pancreas does not have ducts; the

hormones (insulin and glucagon) secreted by the islets of Langerhans

are released into the capillaries and from there into the blood circula-

tion. Insulin and glucagons play important roles in regulating blood

glucose levels. Insulin stimulates glucose entry in many cells, thereby

regulating carbohydrate metabolism and lowering blood glucose lev-

els. Glucagon enhances the synthesis and release of glucose from the

liver into the blood, thus increasing blood glucose levels.

Figure 17-14B. Islets of Langerhans, endocrine pancreas. H&E, 462

There are four types of endocrine cells in the islets of Langerhans: alpha cells, beta cells, delta cells, and PP cells. It is difﬁ cult to

distinguish among them in H&E stain. However, the beta cells are usually distributed throughout the islets; the other three types

of cells are commonly found at the periphery of the islets. Alpha cells secrete glucagon, beta cells secrete insulin, delta cells secrete

somatostatin and gastrin, and PP cells secrete pancreatic polypeptide. Secretion of insulin occurs in response to high blood glucose

levels; secretion of glucagon occurs in response to lower blood glucose levels.

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341

Insulin-producing

(beta) cells

Insulin-producing

(beta) cells

Capillaries

Exocrine

secretory

cells

Exocrine

secretory

cells

Endocrine secretory cell

Rough endoplasmic reticulum

Golgi complex

Secretory granules in alpha cell

Erythrocyte in lumen of

fenestrated capillary

Secretory granules

in beta cell

Secretory granules

in beta cell

Figure 17-15A. Pancreatic islet cells, islets of Langerhans.

Immunocytochemistry stain, 189

This is an example of an islet of Langerhans prepared with

a special immunocytochemistry stain for insulin. Cells

with brown color are insulin-producing cells and are the

predominant cells in the islets of Langerhans. Insulin-

producing cells, also called beta cells, are distributed

throughout the pancreatic islets. The background counter-

stain is hematoxylin, which makes the endocrine pancreatic

cells appear light blue with darker blue–stained nuclei.

Type 1 diabetes mellitus is the most common type of dia-

betes in childhood and adolescence (65% of total cases). It

is characterized by insulin deﬁ ciency and sudden onset of

severe hyperglycemia, diabetic ketoacidosis, and death if

patients are left without insulin treatment. Symptoms also

include polyuria, polydipsia, lethargy, and weight loss.

The major cause of the disease is autoimmune destruction

of the insulin-secreting beta cells in the islets of Langerhans

by T cells and humoral mediators (tumor necrosis factor,

interleukin-1, nitric oxide). Treatment options depend

largely on patient and physician preferences and include

baseline doses of insulin plus adjustable premeal doses of

short-acting insulin or rapid-acting insulin analogs.

Figure 17-15B. Pancreatic islet cells, islets of Langerhans. EM, 13,000; inset (color) H&E, 1,632

Pancreatic islet cells, like other types of endocrine cells, are closely associated with fenestrated or sinusoidal capillaries. The granules

of each of the four main types of cells have slightly different characteristic appearances in electron micrographs. Proﬁ les of two dif-

ferent cells are visible in this view. The cell adjacent to the wall of the capillary appears to be an alpha (glucagon-secreting) cell with

small-to-medium granules that have an electron-dense core with a very narrow electron-lucent surround. The proﬁ le in the upper

left appears to belong to a beta (insulin-secreting) cell with larger granules, a less dense core, and a wide lucent area surrounding the

core. The nuclei of the cells are not present in this view, but note that the cytoplasm of the alpha cell exhibits typical features of a

polypeptide synthesizing and secreting cell: Both RER and a large Golgi complex are readily apparent.

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UNIT 3

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Organ Systems

SYNOPSIS 17-1 Pathological Terms for the Endocrine System

Bitemporal hemianopia ■ : A visual ﬁ eld deﬁ cit characterized by loss of both temporal visual ﬁ elds, most often due to com-

pression of the optic chiasm by a pituitary tumor or cyst (Fig. 17-7A,B).

Goiter

■ : A general term for enlargement of the thyroid gland; common causes include benign multinodular goiter, diffuse

toxic goiter, and thyroiditis (Fig. 17-8C).

Osteitis ﬁ brosa cystica

■ : A cystic bone lesion seen in patients with hyperparathyroidism due to increased osteoclast activity

and bone resorption caused by elevated parathyroid hormone (Fig. 17-9C).

Polydipsia

■ : Term describing patients with excessive thirst, commonly seen in diabetes mellitus when hyperglycemia causes

osmotic ﬂ uid diuresis with resultant dehydration and thirst (Fig. 17-16).

Polyuria

■ : Term describing excessive urination, commonly seen in diabetes mellitus when hyperglycemia produces osmotic

ﬂ uid diuresis with resultant dehydration and secondary polydipsia (Fig. 17-16).

Amyloid

■ : Extracellular glycoproteins characterized physically by ﬁ brillar ultrastructures and chemically by response to

special staining reactions (Fig. 17-16).

CLINICAL CORRELATION

Figure 17-16.

Type 2 Diabetes Mellitus. H&E, 195

ype 2 diabetes mellitus is characterized by hyperglyce-

mia with normal or elevated insulin levels, in contrast

to type 1 diabetes in which hyperglycemia is associated

with little or no insulin production. In type 2 diabetes,

insulin is present, but insulin-sensitive tissues, such as

skeletal muscle and adipose tissues, manifest resistance

to the action of insulin. Defects in beta cell function

also contribute to the disease process. Type 2 diabetes

generally has an insidious onset and typically affects

adults. Risk factors include genetic factors and a strong

association with obesity. Approximately 85% of type 2

diabetes is associated with obesity. Clinically, patients

present primarily with polyuria and polydipsia due to

the hyperglycemia. Chronic hyperglycemia leads to

accelerated atherosclerosis and small vessel damage,

which affects the eyes (retinopathy), kidneys (neph-

ropathy), and nerves (neuropathy). Early in the disease,

the islets of Langerhans become hyperplastic in order

to produce more insulin. Later in the disease, the islets

become atrophic with amyloid deposition. Treatment

includes diet modiﬁ cation and exercise to induce weight

loss and the use of oral hypoglycemic medications.

Some patients may require insulin late in the disease

process because of progressive loss of beta cells.

Amyloid

replacing

islet of Langerhans

Exocrine

pancreas

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CHAPTER 17

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Endocrine System

343

Gland Name Hormone

producing Cells

Hormone Produced Target Tissues and

Organs

Main Functions

Pituitary Glands

Adenohypophysis

(anterior pituitary)

Acidophils:

Somatotrophs

Mammotrophs

Growth hormone

Somatotropin

Prolactin

Liver (primary); bone,

muscle, and adipose tissue

(secondary)

Mammary gland

Stimulate body growth

Stimulate mammary glands to produce

milk

Basophils:

Corticotrophs

Thyrotrophs

Gonadotrophs

ACTH and

corticotropin

TSH

FSH

Adrenal cortex

Thyroid gland

Ovaries

Testes

Stimulate secretion of glucocorticoids and

androgens

and T

Stimulate oocytes to develop and promote

estrogen secretion

Stimulate testes to produce sperm

Neurohypophysis

(posterior pituitary)

Neurosecretory

cells from

hypothalamus

Vasopressin/ADH

Oxytocin

Collecting tubules of

kidney; smooth muscle in

arterioles

Uterus, mammary gland

Promote collecting tubules’ permeability

to water

Stimulate contraction of uterus and

mammary gland

Thyroid Gland

Follicular cells

Parafollicular cells

and T

Calcitonin

Most tissues of body

Bone

Increase metabolic rate; inﬂ uence body

growth and development

Inhibit osteoclasts’ absorption activity and

reduce blood calcium level

Parathyroid Gland

Chief cells PTH Bone; small intestine;

kidney

Increase osteoclasts’ absorption activity and

increase blood calcium level

Adrenal Gland

Adrenal cortex Secretory cells in

zona glomerulosa

Secretory cells in

zona fasciculata

Secretory cells in

zona reticularis

Mineralocorticoids

(aldosterone)

Glucocorticoids (cortisol

or hydrocortisone;

corticosterone)

Weak androgens

(dehydroepiandrosterone,

androstenedione)

Renal tubules of the

kidney

Liver; immune cells (such

as T and B lymphocytes

and macrophages); muscle

and adipose tissue

Testes; uterine and

mammary glands; other

tissue, such as bone, hair,

etc.

Inﬂ uence salt and water balance by

promoting renal tubule reabsorption of

and water and secretion of K

Involved in carbohydrate metabolism

and stimulation of gluconeogenesis in

the liver; immunosuppressive; reduces

muscle and adipose tissue uptake of

glucose

As weak androgens, can be converted to

either testosterone or estrogen; contribute

to sex characteristics and reproduction

Adrenal medulla Chromafﬁ n cells:

Adrenaline

secreting cells

Noradrenaline

secreting cells

Adrenaline (epinephrine)

Noradrenaline

(norepinephrine)

Heart; blood vessel; liver

and adipocytes

Increase heart rate and cardiac output;

constrict blood vessels in organs and

increase blood ﬂ ow to heart and to

skeletal muscle

Increase release of glucose and fatty acids

into blood; dilate pupils, and prepare body

for action.

Pineal Gland

Pinealocytes Melatonin

Serotonin

Hypothalamus Regulate circadian rhythms; promote sleep

and control sexual activity; enhance mood

and slow the aging process

Endocrine Pancreas

Alpha

Beta,

Delta

PP cells

Glucagon

Insulin

Somatostatin

Pancreatic polypeptide

Liver; gastric glands;

exocrine pancreas

Regulate blood glucose levels; stimulate

gastric gland secretion; inhibit exocrine

pancreatic secretion

ACTH, adenocorticotropic hormone; TSH, thyroid-stimulating hormone; FSH, follicle-stimulating hormone; LH, luteinizing hormone; ADH, antidiuretic

hormone; T

, triiodothyrodine; T

, thyroxine; PTH, parathyroid hormone; PP cells, pancreatic polypeptide cells.

TABLE 17-1 Endocrine Organs

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344

Male Reproductive

System

Introduction and Key Concepts for the Male Reproductive System

Figure 18-1 Overview of the Male Reproductive System

Figure 18-2 Orientation of Detailed Male Reproductive System Illustrations

Testis

Figure 18-3A Overview of the Testis

Figure 18-3B,C Seminiferous Tubules of the Testis

Figure 18-4A Cells in the Seminiferous Tubules

Figure 18-4B Seminiferous Epithelium

Figure 18-5 Seminiferous Epithelium, Early Spermatid

Figure 18-6A Sertoli Cells, Seminiferous Tubules

Figure 18-6B Sertoli Cell and Primary Spermatocyte, Seminiferous Epithelium

Figure 18-7 Interstitial Cells of Leydig

Synopsis 18-1 Functions of Sertoli Cells

Synopsis 18-2 Functions of Testosterone

Figure 18-8 Hormone Regulation Involving the Testicular Cells

(Interstitial Cells of Leydig and Sertoli Cells)

Figure 18-9 Overview of Readily Identiﬁ able Spermatogenic Cells in the Seminiferous Epithelium

Figure 18-10 Overview of Spermatogenesis and the Stages of the Seminiferous Epithelium

Figure 18-11A Stage I Seminiferous Epithelium

Figure 18-11B Stage II Seminiferous Epithelium

Figure 18-12A Stage III Seminiferous Epithelium

Figure 18-12B Stage IV Seminiferous Epithelium

Figure 18-13A Stage V Seminiferous Epithelium

Figure 18-13B Stage VI Seminiferous Epithelium

Intratesticular Genital Ducts

Figure 18-14A Intratesticular Genital Ducts

Figure 18-14B Tubuli Recti

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