Histology Exam #2

what are the functions of the endocrine system? list 3

• Regulate activities (cells, tissues, organs)

• Maintains homeostasis

• Coordinating growth + development

what tissues is the endocrine glands made up of?

Made up of islands of epithelial + glandular tissue

• Tissues are vascularized w/ capillaries--> in btw cords/clumps of secretory cells

what do endocrine glands secrete?

Secretes chemical messengers: hormones into blood stream

what are the 4 main groups of chemicals that act as hormones in the endocrine glands?

1. Steroids

2. Peptides

3. Proteins

4. Amines

the endocrine is divided into 3 parts, what are they?

1. Endocrine organs

   • only function is synthesis, storage, and secretion of hormones

   • Endocrine organs include: pituitary, pineal gland, thyroid, parathyroids, and adrenals

2. Components of other organs

   • clusters of endocrine cells are found in organs with other function such as pancreas, ovaries, and testes.

3. Diffuse endocrine system

   • individual cells found among the epithelium lining the gastrointestinal tract and the respiratory tract form the diffuse neuroendocrine system

list 5 characteristic of pituitary: shape, location, attached to what, referred to as what, under what control?

• Small bean shape organ

• Lies in bony depression in base of skull

• Attached to hypothalamic region of brain stalk

• Referred to as "master" gland

  • Controls activity of endocrine glands

• Under control of hypothalamus

what are the 2 major regions of the pituitary?

1. Anterior pituitary

   • also called adenohypophysis

   • glandular epithelium

   • secretes tropic which modulate other glands and direct action hormones which act on non-endocrine tissue

2. Posterior pituitary

   • also called neurohypophysis or pars nervosa

   • nervous tissue

   • stores vasopressin (ADH) and oxytocin

What is the older classification of the anterior pituitary secretory cells? list 2

• Secretory cells of AP were once classified according to their affinity for hematoxylin/eosin as:

  • Chromophils

    • Basophils

    • Acidophils

  • Chromophobes

    • Resting or degranulated chromophils

what is the newer classification of the anterior pituitary secretory cells? list 5

• Now classified based on their hormone content as:

  • Somatotrophs – growth hormone

  • Mammotrophs – prolactin

  • Corticotrophs – corticotrophin (ACTH) , lipotropins, and endorphins

  • Thyrotrophs – thyrotrophin (TSH)

  • Gonadotrophs – follicle stimulating hormone (FSH), and luteinizing hormone (LH)

how is precise identification of hormone content of the anterior pituitary done?

• Precise identification of hormone content--> done using hormone/antibody immunohistochemistry methods

  • One cell produced 1 type of hormone--> except in LH + FSH

    • LH + FSH--> identified w/in single cell

what supports secretory cells? what is it surrounded by?

• Clumps of secretory cells are supported by basement membrane

  • Surrounded by sinusoidal capillaries + stroma of collagen + reticulin

what do the axons of the posterior pituitary consist?

• Axons of posterior pituitary consist of non-myelinated axons of neurosecretory cells

  • located in hypothalamus

what do the neuron cell bodies synthesize and release in the posterior pituitary? what controls the secretion?

• Neuron cell bodies synthesize + release ADH + oxytocin down axon to posterior pituitary--> where it is stored

  • Form Herring bodies: distended terminations

• Secretion is controlled by nervous impulses from axons of hypothalamus in neurosecretion (process/structure)

list 4 characteristics of the thyroid

• Lobulated gland

• Lies anterior to trachea

• Produces hormones important for regulation of basal metabolic rate

• Hormones contain iodine

list the 3 hormones of the thyroid

1. tri-iodothyronine (T3)

2. thyroxine (tetra-iodothyronine (T4))

3. Calcitonin: produced by thyroid + responsible for calcium homeostasis

describe the lobes of the thyroid

• Have 2 lateral lobes

  • Connected by isthmus

  • Thin collagen capsule + septa--> divides organ in lobules

    • Septa carries blood vessels, lymphatics, nerves

  • Functional unit of thyroid: thyroid follicle

how are thyroid follicle formed?

• Each thyroid follicle--> formed by single layer of cuboidal epithelium bound by basement membrane

describe the lumen of the thyroid

• Enclosed lumen is filled w/ colloid--> eosinophilic homogenous proteinaceous + rich in thyroglobulin

  • Stores T3 + T4 prior to secretion

describe the follicles of the thyroid

• Small amts of fine fibrocollagenous tissue--> rich in capillaries lie btw follicles

• Size of follicle + height of thyroid epithelium--> varies

  • Depends on if thyroid is actively synthesizing/breaking down thyroid hormones OR in resting phase

what type of epithelium does the thyroid have?

• Epithelium appear flat/cuboidal when inactive

  • Become tall columnar when active (synthesizing/secreting)

what are C cells?

• Thyroid C cell ("clear" cells):

  • Produce calcitonin

  • Calcitonin: lowers blood calcium levels

    • Discovered in dogs

    • In clusters in fibrocollgenous tissue btw follicles

  • "parafollicular" cell was originally used for C cells

where are C cells located?

• In humans--> was thought that C cells lie adjacent to thyroid epithelial cells + w/in basement mem

  • Not in contact w/ colloid

  • Immunocytochemical methods--> may be used to distinguish these cells

how many parathyroids does human have?

• Most humans have 4

  • Some have 8

what are parathyroid anatomically associated with?

• very small parathyroid glands anatomically associated with the thyroid

what does the parathyroid secrete?

• Secrete parathormone (parathyroid hormone – PTH): involved in calcium homeostasis

• Parathyroid hormone raises serum calcium levels

what are the parathyroid glands covered by?

• Parathyroid glands are covered by a delicate capsule with septa

  • There is a cord and clump arrangement of cells associated with a capillary network

what are the 2 types of parathyroid?

1. Chief cells

   • Secrete PTH

   • Small (5-8µ) in diameter

   • Eosinophilic

   • Small dark nucleus

   • Numbers vary depending on calcium balance

   • Act on bones, kidneys and intestines to increase amount of available calcium

2. Oxyphil cells

   • Inactive cells of same cell type as chief cells

   • Less numerous than chief cells

   • Larger (6-10µ) and deeply stained with eosin

what are present after puberty in the parathyroid?

• Adipocytes are present in the parathyroid after puberty, and may occupy 60% of the gland in elderly persons

what is the adrenal cortex covered by?

connective tissue capsule

what are the 3 zones of the adrenal cortex?

1. Zona Glomerulosa (outer layer)

   • Cells arranged in small rounded clusters

   • Produces mineralocorticoids, mainly aldosterone

2. Zona Fasciculata (middle layer)

   • Broadest zone; cells arranged in long cords with straight fenestrated capillaries

   • Cells appear foamy due to lipid droplets (cholesterol derivatives)

   • Secretes glucocorticoids, primarily cortisol.

3. Zona Reticularis (inner layer)

   • Cells arranged in an irregular network

   • Smaller, darker-staining cells

   • Produces androgens and some glucocorticoids.

list 3 characteristics of the adrenal medulla

• Contains large, pale-staining cells clustered around blood vessels

• Secretes catecholamines (epinephrine and norepinephrine)

• Cells contain granules that turn brown with chrome salts → called chromaffin cells

describe the blood supply of the adrenal glands + the medulla

• Glands need rich vascular supply

• Arterial supply forms plexus of small arteries around capsule

• Some arteriole branches form cortical capillaries--> some arterioles pass directly to medullary region

• In medulla

  • blood medullary sinuses is collected into medullary veins

  • Blood that has percolated thru cortex also collected here

what does the endocrine pancreas consist of? color of stain? location?

• Islets of Langerhans: endocrine portion of pancreas

• Pale staining

• Scattered among exocrine pancreas

• Each islet has capillary network--> in contact w/ each cell

what are the 2 main secretions of the endocrine pancreas?

• Insulin

• Glucagon

  • Plays role in carb metabolism

what are the 4 cell types of the islets of Langerhans?

1. Beta cells (60–70%)

   • Produce insulin and amylin

2. Alpha cells (20–25%)

   • Produce glucagon

3. Delta cells (5–10%)

   • Produce somatostatin

4. PP (or F) cells (1–2%)

   • Produce pancreatic polypeptide

Location of neuroendocrine cells

• Neuroendocrine cells are widely scattered throughout the gastrointestinal and respiratory tract epithelium

what are the neuroendocrine system referred as historically?

• Historically referred to as the APUD system (Amine Precursor Uptake and Decarboxylation)

what is the function of the Neuroendocrine system?

• Work together with the autonomic nervous system to regulate GI and respiratory tract activity

list 4 histology characteristics of the Neuroendocrine system?

• Hard to see on H&E stain

• Small, pale-staining cells located near the basement membrane

• Do not reach the lumen

• Best visualized with immunohistochemical staining

what were the old terminology of the neuroendocrine system?

• Previously identified using silver stains

• Old names: argentaffin and argyrophil cells

what is the male reproductive system responsible for? list 3

• nourishment

• temp storage of sperm

• Synthesis + secretion of male sex hormones

what is the female reproductive system responsible for? list 4

• Production of ova

  • provides suitable environment for fertilization + development of the fetus

  • giving birth to the developed fetus

  • nutrition of the newborn

  • secretion of female sex hormones

what are the components of the female reproductive system? List 6

1. Ovaries: Produce ova through the process of oogenesis and are also endocrine in function

2. Oviducts: Convey ova from the ovary to the endometrial lining of the uterus

3. Uterus: A muscular organ, consisting of three areas, which are adapted to provide a suitable environment for implantation and nourishment of the embryo

4. Vagina: A fibromuscular tube extending from the vestibule to the cervix forming the lower portion of the birth canal

5. Vulva: External genitalia- modified skin

6. Breast: Glandular tissue which produces milk following birth

describe the ovary shape, location, + what each organ divides into

• Ovaries are paired

• Small ovoid organs lying in lateral pelvic cavity

• Each organ is divided into highly cellular cortex + richly vascularized medulla

what type of epithelium is on the surface of the ovary? what outdated term is used for the ovary covering?

• Surface of ovary: covered by single layer of low cuboidal epithelium, continous w/ peritoneum at hilum of ovary

• Germinal epithelium: used for ovary covering

  • Misleading old term--> epithelium is X source of ova

what is below the epithelium layer of the ovary?

 basement mem + dense eosinophilic layer (tunica albuginea)

what are the 2 major components of the ovarian cortex?

1. Stroma and stromal cells

2. Numerous ovarian follicles in various stages of maturation

what are stromal cells?

• Spindle shaped cells

• Gives strucutral support to developing ova

• Form thecal layers of developing follicle + secrete estrogen + progesterone

how many primordial germ cells (oocytes) are present in the cortex at birth?

~400,00

what happens to the follicles at puberty?

• Some primordial follicles continue to develop--> under influence of follicle stimulating hormone (FSH) from pituitary

what happens to the follicles at each monthly cycle?

• 1 follicle matures + releases an egg

• Mature follicle= Graafian follicle

what happens to the follicle at ovulation? what simulates ovulation? where does the egg expel to?

• Graafian follicle can be seen w/ naked eye

  • Budge on ovary surface

• Stimulus to ovulate: surge of luteinizing hormone (LH) from pituitary

• Egg is expelled into peritoneal cavity near fallopian tubes

what is the ovarian medulla?

• Highly vascular w/ coiled arteries + veins

  • Gives extensive capillary bed--> radiates to cortex + is in close association with follicles

describe the shape of the uterus

• Thick walled

• Pear shaped

• Muscular organ

what is the uterus divided into? name 3. any commonalities?

1. Fundus

2. The body

3. The cervix

• Fundus + body--> have same histological strucuture

• Cervix--> cylindrical neck region

what 2 linings does the fundus body have?

1. myometrium

2. endometrium

what is the myometrium? what is it composed of? list 3.

• Thick muscular wall of the uterus

• Composed of three indistinct smooth muscle layers:

  1. Central layer: thick and circularly arranged

  2. Inner layer: more oblique

  3. outer layer: more oblique

what happens during pregnancy in the fundus body?

• Smooth muscle undergoes hypertrophy (increase in cell size)

• And hyperplasia (increase in cell number)

• Changes occur in response to high estrogen levels

what is the endometrium? what happens to it during menstrual cycle?

• Inner lining of the uterus

• Undergoes cyclic, hormone-regulated changes during the menstrual cycle

what is the structure of the endometrium?: epithelium, gland shape

• Simple columnar epithelium

• Epithelium forms simple tubular endometrial glands

• Lamina propria beneath the epithelium = endometrial stroma

what are the 2 layers of the endometrium? what control the changes of the endometrium?

1. Functional layer (superficial): shed during menstruation

2. Basal layer: remains after menstruation; regenerates the functional layer

• Changes driven by ovarian hormone secretion patterns

what is cervix?

• Lower part of the uterus that projects into the vagina

• Endocervical canal connects the endometrial cavity to the vagina

what is the cervix stroma made of?

• Mostly fibrocollagenous tissue

• Contains little smooth muscle

what is Endocervical canal epithelium?

• Simple columnar epithelium that secretes mucin

• Epithelium forms indentations/furrows into the lamina propria (sometimes called “tubular glands,” though not truly glands)

what is the Squamo-columnar junction (SCJ) in the cervix?

Transition from simple columnar epithelium to stratified squamous non-keratinized epithelium covering the ectocervix

what is the function of the fallopian tube? (Uterine Tube / Oviduct)

• Functions to capture the ovulated egg via the fimbriae

• Transports the egg from the pelvic cavity toward the uterus

what are the 4 segments of the fallopian tube?

1. Intramural – passes through the myometrial wall

2. Isthmus – narrow, thick-walled region

3. Ampulla – long, thin-walled segment (site of fertilization)

4. Infundibulum – flared end with fimbriae

describe the epithelium + associated cells of the fallopian tube? list 3

• Lined with tall columnar ciliated cells and secretory cells

• Ciliated cells: help move the ovum

• Secretory cells: produce watery tubal fluid for nutrition and protection of the ovum

what is the wall structure of the fallopian tube made of?

• Lamina propria: delicate connective tissue beneath epithelium

• Smooth muscle layers:

  • Inner layer: tight spiral → appears circular

  • Outer layer: loose spiral → appears longitudinal

list 3 characteristics of the Breast tissue

• Each breast contains 15–25 glandular units (lobes)

• Each lobe is a compound tubulo-acinar gland

• Lobes are arranged radially around the nipple at different depths

Lobules & Duct System of the breasts: how is it divided? what does the lobules contain? duct epithelium?

• Each lobe is divided into lobules

• Lobules contain:

  • Alveolar ducts

  • Clusters of terminal ductules

• Duct epithelium:

  • Simple columnar or cuboidal

  • Outer layer of discontinuous myoepithelial cells

describe the connective tissue of the breasts.

• Lobules embedded in loose fibrous connective tissue

• This is surrounded by dense fibrocollagenous tissue + adipose tissue

what are Lactiferous Ducts & Sinus?

• Each lobe drains into a single lactiferous duct

• The duct opens separately on the nipple

• Before opening, it expands to form the lactiferous sinus

describe the nipple strucutre

• Contains smooth muscle bands:

  • Longitudinal (parallel to ducts)

  • Circular (near the base)

• Smooth muscle contraction → nipple erection

What surrounds the nipple? what does it contain? what is the purpose of their secretions?

• The areola is pigmented skin surrounding the nipple

• Contains sebaceous glands not associated with hair follicles

• Their secretions likely protect the nipple and areola during suckling

list 3 changes in the breast during pregnancy

• Progesterone stimulates formation of alveolar secretory units

• These units begin producing a serous fluid in the third trimester

• True milk production starts several days after birth (parturition)

what are the 4 components of the male reproductive system?

• Testes:

  • Produce spermatozoa

  • Synthesize and secrete androgens

• Epididymis, vas deferens, ejaculatory duct, part of male urethra:

  • Ductal system to carry spermatozoa to exterior

• Seminal vesicles, prostate gland, bulbiurethral glands:

  • Secretory glands to provide fluid and nutrients to support and nourish spermatozoa

• Penis:

  • Organ responsible for carrying a suspension of spermatozoa into the female reproductive tract

what are the testes?

• Pair of compact ovoid organs located in the scrotum

what are the testes covered in?

• Completely covered by a thick fibrocollagenous capsule called the tunica albuginea

• The tunica albuginea divides the testis into 200–300 lobules

• Each lobule contains 1–4 seminiferous tubules (sites of sperm production)

what does the duct system for sperm transport consist of? list 4

• The testes connect to a paired duct system that collects, stores, and transports spermatozoa, consisting of:

  1. Efferent ducts (ductuli efferentes)

  2. Epididymis

  3. Vas deferens (ductus deferens)

  4. Ejaculatory duct

what is the Seminiferous Tubules? what is it lined with? what are the associated cells?

• Site of sperm production in the testes

• Lined by germinal epithelium + Sertoli cells (supporting cells)

• Leydig cells lie in the interstitial space between tubules and secrete testosterone

what is Spermatogenesis?

• Spermatogonia (basal layer) = spermatogenic stem cells capable of extensive mitosis

• Spermatogenesis = process of producing spermatids

• Spermiogenesis = transformation of spermatids into spermatozoa; occurs in four stages

what are sertoli cells?

• Tall columnar cells extending from basement membrane to lumen

• Provide structural + metabolic support (“nurse cells”) to developing sperm

• Also have phagocytic functions

• Contribute to the blood–testis barrier (not in your text but useful knowledge)

what are leydig cells?

• Located in interstitial tissue between seminiferous tubules

• Endocrine cells that synthesize and secrete testosterone

what are myoid cells?

• Found around the outer walls of seminiferous tubules

• Contractile cells containing intermediate filaments and desmin

• Help move sperm and fluid through the tubules

where are vas deferens located?

Located within the spermatic cord along with arteries, veins, lymphatics, and nerves

describe the structure of the vas deferens

• Travels to the base of the bladder

• Joins a duct from the seminal vesicle → forms the ejaculatory duct

• Ejaculatory ducts pass through the prostate and open into the prostatic urethra

what is the small lumen of the van deferens lined by?

• Small lumen lined by pseudostratified columnar epithelium with stereocilia

• Underlain by a fibrocollagenous lamina propria; mucosa appears folded

what are 3 layers of the muscular wall of the van deferens?

• Inner longitudinal

• Middle circular

• Outer longitudinal

what attaches to the sperm cords?

• Has a loose fibrocollagenous adventitia attaching it to spermatic cord structures

• Duct severed during a vasectomy

what is the prostate? what is it made of? epithelium of secretory vs. urethra?

• Produces a major portion of seminal fluid, along with seminal vesicles

• Made of branched tubulo-acinar glands arranged concentrically around the prostatic urethra

• Secretory epithelium varies from pseudostratified to tall columnar depending on activity

• Prostatic urethra is lined by transitional epithelium

what to the gland lumens contain? what does the stroma contain? what is the prostate surrounded by?

• Gland lumens may contain corpora amylacea (spherical proteinaceous concretions)Stroma contains fibrocollagenous tissue and smooth muscle

• Surrounded by a capsule with septa dividing it into lobule-like regions

• Surrounded by a capsule with septa dividing it into lobule-like regions

Histology

study of cells + microscopic strucuture of tissue

Histopathology

study of microscopic strucuture of diseased tissue

Pathology

study of nature + cause of disease, involves changes in strucuture + functions--> condition produced by disease

Anatomic pathology

field of pathology that deals w/ structural changes in disease

Surgical pathology

application of pathological procedures + techniques for investigating tissues removed surgically

Histopathology techniques

preparation of organs, tissues, or tissue components for microscopic study

Pathologist

specialist in diagnosing abnormal changes in tissues removed at operations + postmortem examination

what is the routine pathology lab?

• Where tissues that have been received from surgery + autopsy + cytological specimens are prepared for microscopic examination