Endocrine APR - Lab

Insulin

Produce by the pancreas when blood glucose (sugar) level increases

Insulin Effect on our Body

Causes body cells, especially skeletal muscle fibers and liver cells (hepatocytes), to take in glucose, thus removing glucose from the blood and lowering the blood glucose level

Insulin effect on Homeostasis

It’s the only control mechanism that causes the blood glucose level to decrease

Pancreas Diagram

Pancreas is an exocrine and endocrine organ

Normoglycemia

• A normal level of blood glucose

  • Regular, smooth swimming is a sign of normal behavior in fish

Hyperglycemia

• An abnormally high level of blood glucose

  • Fast, darting movements are signs of hyperglycemia in fish

Hypoglycemia

• An abnormally low level of blood glucose

  • Slow, lethargic movements and difficulty moving are signs of hypoglycemia in fish.

  • Excess insulin can induce a state of hypoglycemia called insulin shock.

After extensive exercise, a person with diabetes is feeling dizzy, sweating, shaky, and tired. What could this person do to improve the situation?

Have the person consume food or drink containing glucose

ENDOCRINE APR

Pituitary Gland Function

• Anterior pituitary produces the following hormones:

  • thyroid-stimulating (TSH)

  • prolactin (PRL)

  • adrenocorticotropic (ACTH)

  • growth (GH)

  • luteinizing (LH)

  • melanocyte-stimulating (MSH)

  • follicle-stimulating (FSH)

• Posterior pituitary stores and releases: antidiuretic hormone (ADH) and oxytocin (OT)

Pituitary Gland

• Location:

  • Midline of middle cranial fossa

  • Rests in hypophysial fossa of sphenoid bone

• Description:

  • Small, oval, bilobed endocrine gland

  • Two functional lobes: anterior (adenohypophysis) and posterior (neurohypophysis)

  • Connected by the infundibulum to the hypothalamus
    Also known as:

  • Hypophysial gland or hypophysis

• Comment:

  • Posterior pituitary does not produce any hormones; ADH and OT are produced in the hypothalamus

Infundibulum of Pituitary Gland

• Location:

  • Ventral surface of diencephalon (hypothalamus) at midline

• Description:

  • Contains hypothalamo-hypophysial tract

  • Contains hypothalamo-hypophysial portal vein that carries hypophysiotropic hormones to the anterior pituitary

• Function:

  • Transmits antidiuretic hormone (ADH) and oxytocin through hypothalamo-hypophysial tract to posterior pituitary

• Comment:

  • Latin: infundibulum = a funnel

Hypothalamus

• Location:

  • Ventral diencephalon

• Description:

  • Collection of nuclei located inferior to thalamus

  • Includes infundibulum and mammillary bodies

Hypothalamus Function

• Considered master control center for endocrine system

• Secretes releasing and inhibiting hormones that control anterior pituitary gland

• Produces hormones that are transported to and stored in posterior pituitary gland

• Controls autonomic nervous system

• Regulates body temperature, food, and water intake

• Regulates emotional behavior

• Maintains sleep/wake cycle

Pineal Gland

• Location:

  • Diencephalon (epithalamus)

• Description:

  • Pea-sized endocrine gland

  • Attached to roof of third ventricle

• Also known as:

  • Pineal body

Pineal Gland Function

• Secretes melatonin (involved in sleep/wake cycles)

• Modified activity in endocrine organs (pituitary, pancreas, parathyroid, suprarenal, and gonads)

Thyroid Gland

• Location:

  • Neck (anterior inferior)

• Description:

  • Bilobed endocrine gland

  • Normally composed of left and right lateral lobes connected across midline by isthmus of gland

  • An additional, superiorly-directed, conical pyramidal lobe present 50% of the time

Thyroid Gland Function

• Function:

  • Follicular cells: synthesize and secrete thyroid hormones T3 (triiodothyronine) and T4 (thyroxine)

  • Parafollicular cells: synthesize and secrete calcitonin

• Comments:

  • Lobes lie lateral to trachea and larynx

  • Enlarged thyroid gland known as a goiter, typically due to insufficient dietary iodine

Lateral Lobe of Thyroid Gland

• Location:

  • Lateral and anterior to trachea and larynx

• Description:

  • Paired, elongated, lateral extension from isthmus

Lateral Lobe of Thyroid Gland Function

• Synthesizes and secretes thyroid hormones T3 (triiodothyronine) and T4 (thyroxine)

• Synthesizes and secretes calcitonin

Pancreas

• Location:

  • Abdomen

  • Posterior to stomach

  • In upper abdominal quadrants; in epigastric region and left hypochondriac region (tail)

• Description:

  • Accessory digestive organ

  • Elongated nodular gland

  • Divided into head, neck, body, and tail

  • Head adjacent to duodenum

Pancreas Function

• Function:

  • Endocrine (regulation of glucose metabolism): pancreatic islet cells release hormones (insulin, glucagon, and somatostatin) into blood

  • Exocrine (digestion): acinar cells produce digestive enzymes (pancreatic juice) and pancreatic duct cells produce bicarbonate ions; these are released into duodenum via pancreatic ducts

• Comment:

  • Reduction in insulin production or release by pancreatic islet cells can result in diabetes mellitus

Head of Pancreas

• Location:

  • Abdomen (right upper quadrant)

  • Adjacent to duodenum

• Description:

  • "C" shape conforms to duodenum

  • Contains junction of bile and main pancreatic ducts that form hepatopancreatic ampulla

• Comment:

  • Reduction in insulin production or release by pancreatic islet cells can result in diabetes mellitus

Body of Pancreas

• Location:

  • Pancreas

• Description:

  • Between neck and tail of pancreas

• Comment:

  • Splenic artery and vein course along superior border

  • Reduction in insulin production or release by pancreatic islet cells can result in diabetes mellitus

Tail of Pancreas

• Location:

  • Abdomen (left upper quadrant)

  • Posterior to stomach

  • Tip of tail adjacent to spleen

• Description: Elongated part of gland

• Comment: Reduction in insulin production or release by pancreatic islet cells can result in diabetes mellitus

Suprarenal gland

• Locations:

  • Abdomen (upper quadrants)

  • Adjacent to superior pole of kidney

• Description:

  • Paired; pyramidal-shaped, endocrine gland

  • Two parts: cortex (outer) and medulla (inner)

• Also known as: Adrenal Gland

• Comment: Epinephrine and norepinephrine, also known as adrenaline and noradrenaline

Suprarenal gland Function

• Cortex: secretes hormones (corticosteroids and androgen)

• Medulla: chromaffin cells secrete catecholamines (epinephrine and norepinephrine)

Suprarenal Capsule

• Locations: Surrounds suprarenal (adrenal) gland

• Description: Connective tissue

• Also known as: Adrenal Capsule

Suprarenal Cortex

• Locations: Outer part of suprarenal (adrenal) gland

• Description:

  • Lipid-rich, yellowish outer part of gland

  • Three regions: zonula glomerulosa, zonula fasciculata, and zonula reticularis

• Also known as: Adrenal cortex

• Comment: Disorders of suprarenal cortex hormone secretion include Addison's disease and Cushing's syndrome

Suprarenal Cortex Function

• Zonula glomerulosa produces mineralocorticoids (e.g., aldosterone) that regulate sodium/potassium ratio in blood and body fluids

• Zonula fasciculata produces glucocorticoids (e.g., cortisol) that stimulate lipid and protein metabolism, and regulate blood glucose levels

• Zonula reticularis produces steroid sex hormones called gonadocorticoids (e.g., dehydroepiandrosterone or DHEA)

Suprarenal Medulla

• Locations: Central part of suprarenal (adrenal) gland

• Description:

  • Reddish-brown, core of gland

  • Composed primarily of chromaffin cells

• Also known as: Adrenal medulla

Suprarenal Medulla Function

Produces epinephrine (adrenaline) and norepinephrine (noradrenaline) that work with sympathetic nervous system in "fight-or-flight" responses

Ovary

• Locations:

  • Pelvis (lateral wall)

  • Near distal end of uterine tube

  • Extends into lower abdominal quadrants

• Description:

  • Paired, female gonad

  • Almond shape and size

  • Contains oocytes (egg)

• Comment:

  • Suspended by mesovarium of broad ligament (a peritoneal fold)

  • Suspensory ligament of ovary (a peritoneal fold) contains ovarian vessels and nerves

  • Size decreases after menopause

Ovary Function

• Maturation (oogenesis) and release (ovulation) of oocytes

• Produces the female sex hormones progesterone, estrogen, and inhibin

Testis

• Locations: Scrotum

• Description:

  • Paired, oval, male gonad

  • Dense outer capsule (tunica albuginea testis)

  • Interior divided into 200-300 lobules

  • Each lobule contains up to three seminiferous tubules

Testis Function

• Function:

  • Produces sperm cells

  • Produces androgens (male sex hormones) such as testosteron

• Comment:

  • Plural: testes

  • The testis begins development near the kidney, and later descends along the posterior abdominal wall to the scrotum

  • Development of sperm cells is temperature dependent (scrotal temperature ~3° lower than body cavity)

  • Temperature of testis regulated by: (1) distance from body cavity, and (2) heat exchange between testicular artery and pampiniform venous plexus

  • Testosterone regulates hair pattern, sperm production, skeletomuscular growth, and libido

Anterior Piutiary

• Location:

  • Anterior aspect of pituitary gland (pars distalis, pars intermedia)

  • Around pituitary stalk (pars tuberalis)

• Description:

  • Glandular part of pituitary gland

  • Three divisions: pars distalis, pars intermedia, and pars tuberalis

  • Pars distalis consists of chromophil cells (two subtypes: acidophil and basophil) and chromophobe cells

  • Pars distalis consists of basophils and colloid-containing cysts that are lined by a cuboidal epithelium

  • Pars tuberalis consists of basophils

  • Extensive capillary network is present

Anterior Pituitary Function

• Function:

  • Synthesizes and secretes:

    • thyroid-stimulating hormone (TSH)

    • prolactin (PRL)

    • adrenocorticotropic hormone (ACTH)

    • growth hormone (GH)

    • luteinizing hormone (LH)

    • melanocyte-stimulating hormone (MSH)

    • follicle-stimulating hormone (FSH)

• Comment:

  • Anterior pituitary develops as extension of oral cavity epithelium

  • Pituitary also known as hypophysis

  • Anterior pituitary also known as adenohypophysis; sometimes equated with pars distalis

  • Posterior pituitary also known as neurohypophysis; sometimes equated with pars nervosa

  • Chromophil cells have affinity for histological dyes; chromophobe cells stain weakly with histological dyes

Infundibulum of Pituitary Gland

• Location: Ventral surface of diencephalon (hypothalamus) at midline

• Description:

  • Contains hypothalamo-hypophysial tract

  • Contains hypothalamo-hypophysial portal vein that carries hypophysiotropic hormones to the anterior pituitary

• Comment: Latin: infundibulum = a funnel

Infundibulum of Pituitary Gland Function

Transmits antidiuretic hormone (ADH) and oxytocin through hypothalamo-hypophysial tract to posterior pituitary

Posterior Pituitary

• Location:

  • Posterior aspect of pituitary gland (pars nervosa)

  • Infundibulum, between posterior pituitary and hypothalamus

• Description:

  • Posterior aspect of pituitary gland (pars nervosa)

  • Infundibulum, between posterior pituitary and hypothalamus

• Comment:

  • Posterior pituitary develops as inferior extension of hypothalamus

  • Pituitary also known as hypophysis

  • Anterior pituitary also known as adenohypophysis; sometimes equated with pars distalis

  • Posterior pituitary also known as neurohypophysis; sometimes equated with pars nervosa

Posterior Pituitary Function

• Secretes oxytocin and antidiuretic hormone (i.e., ADH or vasopressin); these hormones (synthesized by hypothalamic cells) are transported to posterior pituitary for storage (visible as Herring bodies) and eventually released into capillaries

• Pituicytes support hypothalamic axons

Thyroid Follicle

• Location: Thyroid gand

• Description:

  • Spherical structural units

  • Lined by follicular cells

  • Contains follicular colloid

• Comment:

  • Thyroglobulin is often called colloid

  • Colloid can store up to two weeks supply of thyroglobulin

Thyroid Gland Function

Iodination and storage of thyroglobulin

Follicular Colloid of Thyroid Gland

• Location: Thyroid follicle

• Description: Stored form of secretory product (thyroglobulin) from follicular cells

• Comment:

  • Thyroglobulin is often called colloid

  • Colloid can store up to two weeks supply of thyroglobulin

Nucleus of Follicular Cell of Thyroid Gland

• Location: Follicular cell in thyroid gland

• Description:

  • Largest organelle (5-10 µm in diameter)

  • Spherical or ovoid structure

  • Nuclear envelope comprised of double membrane (i.e., two lipid bilayers)

  • Contains cellular DNA and one or two nucleoli

Nucleus of Follicular Cell of Thyroid Gland Function

• Function:

  • DNA replication

  • DNA transcription into mRNA

  • Ribosomal RNA synthesis and ribosome subunit assembly (in nucleolus)

• Comment:

  • Staining of DNA with basic histological dyes like hematoxylin depends on transcriptional activity: DNA undergoing active transcription, called euchromatin, stains lightly because it is less folded and, therefore, less dense; transcriptionally inactive DNA, or heterochromatin, is tightly packed and condensed and, therefore, stains more darkly

  • Micrometer (µm), also known as a micron, is 1/1,000 of a millimeter

Parafollicular cell of thyroid gland

• Location: Between adjacent follicles of thyroid gland

• Description: Dispersed large cells

• Comment: “C” cell

Parafollicular cell of thyroid gland Function

Produces calcitonin, which lowers blood calclium levels

Pancreatic islet of Langerhans

• Location: Pancreas

• Description: Cluster of cells forming endocrine portion of pancreas

• Comment: endocrine pancreas secretes hormones into bloodstream

Pancreatic islet of Langerhans Function

Produces four hormones:

• Insulin

• Glucagon

• Somatostatin

• Pancreatic Polypeptide

Capillary in pancreatic islet of Langerhans

• Location:

  • Endocrine pancreas

  • Between arterioles and venules

• Description: Fenestrated capillaries

Capillary in pancreatic islet of Langerhans Function

Carries blood and hormones (insulin, glucagon, gastrin, somatostatin, and pancreatic polypeptide) from pancreatic islet of Langerhans

Exocrine Pancreas

• Location: Throughout pancreas

• Description: Tubulo-acinar gland composed of 40-50 acinar cells that surround a lumen formed by centro-acinar cells (beginning of pancreatic duct system)

• Comment:

  • Pancreatic duct system (which forms main and accessory pancreatic ducts) delivers secretions to duodenum at major and minor duodenal papillae (respectively)

  • Acute pancreatitis (inflammation of pancreas) is a condition that involves lysis (dissolving) of pancreatic cells. The most common cause is gallstones that obstruct the outflow of pancreatic enzymes into duodenum and their subsequent "backflow" and impact on pancreatic acini. Chronic, heavy alcohol use is also a common cause.

  • Majority (95%) of pancreatic cancers (adenocarcinomas) affect exocrine portion of the pancreas. Endocrine pancreatic cancer (i.e., islet cell carcinomas) make up approximately 1% of total.

Exocrine Pancreas Function

• Synthesizes and secretes digestive enzymes and proenzymes

• Pancreatic (digestive) enzymes include:

  • pancreatic amylase

  • pancreatic lipase, ribonuclease (RNase)

  • Deoxyribonuclease (DNase)

• Pancreatic proenzymes include: trypsinogen, chymotrypsinogen, procarboxypeptidase, and elastase