Ch 18 Endocrine System Flashcards
4 principal mechanisms of communication between cells
- Gap junctions
- Neurotransmitters
- Paracrine
- Hormones
- Endocrine system
- Glands, tissues, and cells that secrete hormones
- Endocrinology
- Study of endocrine system, diagnosis and treatment of endocrine disorders
- Endocrine glands
- Organs that are traditional sources of hormones
- Nervous system
- Electrical impulses are the messengers
- Pathway = Neuron -> nerve impulse -> neurotransmitter -> target cell
- Endocrine system pathway
- Hormones are the chemical messengers. And target through blood stream
- Endocrine cells -> blood stream -> target cells
endocrine glands
- Thyroid
- Adrenal gland
- Gonads
- Pituitary
exocrine glands
- Liver
- Salivary gland
- Sweat gland
Overview of hormones
- Produced by the endocrine glands
- Chemical messengers (bloodstream)
- Can only affect target cells or target organs
- Cells that do not possess receptors for a specific hormone do not respond to that hormone
Negative and positive feedback loop
- Hormone secretion is regulated by a self adjusting mechanism called feedback loop
- Negative feedback
- Positive feedback
Hypothalamic control of endocrine system
- Hypothalamus is a control center of the endocrine system
- Secretes regulatory hormones that control release of pituitary hormones
- Hypothalamus secretes releasing hormones (RH) and inhibiting hormones (IH)
- Regulates multiple primitive functions - water balance, thermoregulation, sex drive, childbirth
- Many of its functions have closed connections to pituitary gland
Hypothalamus anatomy
- Hypothalamus is shaped like a flattened funnel
- Forms floor and walls of third ventricle
- Hypothalamus contains collection of nuclei surrounding the third ventricle and the mammillary bodies
Pituitary gland
- Also called hypophysis
- Locate inferior to hypothalamus - connected by infundibulum
- Housed in sella tunica of sphenoid bone
Pituitary gland divided into
anterior and posterior
- Anterior pituitary parts
- Pars tubercles
- Pars intermedia
- Pars distills
- Posterior pituitary
- Directly connected to hypothalamus
- Infundibular stalk
- Pars nervosa
Anterior pituitary - adenohypophysis
- Anterior three-quarters of pituitary
- Linked to hypothalamus by hyophysial-portal system
Posterior pituitary - neurohypophysis
- Posterior quarter of the pituitary
- Nerve tissue, not a true gland
- Hypothalamus and neurohypophysis connect through hypothalamo-hypophysial tract
histology of anterior pituitary
- Purple and bulbous
histology of posterior pituitary
- Tan and smaller
RH
releasing hormone = hypothalamus
TRH (thyroid releasing hormone)
PRL (prolactin) (mammary gland) and TSH (thyroid)
GnRH
LH and FSH -> testis and ovaries
CRH
ACTH -> adrenal cortex
GHRH
GH -> liver
Pineal gland
- Located beneath the posterior end of corpus collosum
- After age 7 it shrinks
- Plays a role in circadian rhythm
Thymus
- Plays a role in 3 systems
- Endocrine, lymphatic, immune
thymus location
between lungs above the heart
thymus hormones
- Thymopoietin
- Thyrosin
- Thymulin
Thyroid gland
- Largest gland that has only an endocrine function
thyroid location
- Located inferior to thyroid cartilage and anterior to the trachea
- Butterfly shape with right and left lobes connected by isthmus
- Thyroid follicles
- Sacs that make up most of thyroid
- Follicle lumen
- Contain protein-rich colloid (traps iodine, center of thyroid hormone production)
- Follicular cells
- Simple cuboidal epithelium that lines follicles
Parathyroid glands
- Small gland posterior area of thyroid
- Usually 4
two types of parathyroid cells
- Chief cells: secrete PTH (parathyroid hormone)
- Oxyphil cells: unknown function
Adrenal glands
- Located on superior borders of the kidneys
- Composed of 3 layers producing different corticosteroid
3 layers of adrenal glands
- Zona glomerulosa
-Zona fasciculata- Zona reticularis
- Zona glomerulosa
- Produces mineralocorticoids (aldosterone)
- Zona fasciculata
- Produces glucocorticoids (cortisol)
- Zona reticularis
- Produce gonadocorticoids including androgens
- Adrenal medulla
- Gland’s inner core
- Consist of chromatin cells - modified ganglionic cells of sympathetic nervous system
- Secrete norepinephrine and epinephrine - involved in flight or fight
Pancreas
- Located between duodenum and spleen; posterior to stomach
- Has both exocrine and endocrine functions
Pancreatic acini (exocrine tissue)
produce alkaline secretions into ducts that lead to duodenum for digestion
Pancreatic islets (islets of Langerhans)
small clusters of endocrine cells
4 types of islet cells
- Beta: 80%
- Alpha 10%
- Dela: 3%
- F cell 1%
Diabetes Mellitus
- Most prevalent metabolic disease in the world, ~ 422 million cases
- 34 million in the US
- Due to a hypo secretion of insulin
Diabetes Mellitus symptoms
- Polyuria (excess urine output)
- Polydipsia (intense thirst)
- Polyphagia (hunger)
