L1b - Tissues & Systems (2) Flashcards
Define ‘gland’.
A single or a group of epithelial cells adapted for secretion.
What are the two major types of glands? Describe their characteristics.
- Exocrine Glands (secrete materials directly into ducts or onto the apical epithelial surface; composed of glandular epithelia and secrete mucus, sweat, oil, earwax and digestive enzymes)
- Endocrine Glands (“ductless glands” that secrete materials through the basal surface which diffuses through the basement membrane, connective tissue and into the bloodstream)
Describe the structural features of exocrine glands.
- Unicellular glands
- Goblet cells
- No ducts involved
- Multicellular glands
- Most glands are of this type
- Usually involves ducts
- Duct system can be classified according to shape
Describe the structural features of endocrine glands.
- Ductless, basal secretion
- Secretion diffuses into bloodstream
- Acts at a distant location (hormone)
State the main exocrine gland shapes.
- Simple Tubular Structure
- Compound Tubular Structure
- Simple Alveolar Structure
- Compound Alveolar Structure
(Simple: duct portion does not branch)
(Compound: duct portion branches)
Describe the different types of exocrine gland secretion.
- Holocrine Secretion (Cell accumulates substance for secretion, dies and discharges its content; oil in sebaceous glands)
- Merocrine Secretion (Secretion occurs by exocytosis; sweat glands)
- Apocrine Secretion (Small pieces of cell containing secretion breaks off and cell repairs itself; mammary gland milk lipid droplets)
What are the 2 major control systems of the body?
- Nervous System
- Endocrine System
How does the endocrine system aid communication?
1) Endocrine glands throughout the body secrete hormones - target cells have hormone receptors
2) Hormone binds and initiates or inactivates selective metabolic activities within these cells
List the endocrine organs.
- Pituitary gland
- Thyroid gland
- Pineal gland
- Parathyroid gland
- Adrenal glands
What are endocrine cells found within?
- Hypothalamus
- Skin
- Thymus
- Liver
- Stomach
- Pancreas
- Small intestine
- Gonads (testes and ovaries)
What are endocrine organs?
Single organs that are entirely endocrine in function.
What are endocrine cells?
Present in clusters in organs which have a different primary function.
Describe different endocrine function.
- Maintaining homeostasis of blood composition and volume
- Controlling reproductive activities
- Regulating development, growth and metabolism
- Controlling digestive processes
Name the releasing hormones of the hypothalamus.
- TRH
- PRH
- GnRH
- CRH
- GHRH
Name the inhibitory hormones of the hypothalamus.
- PIH
- GIH
Describe the involvement of the thyroid in the endocrine system.
Thyroid-stimulating hormone (TSH) stimulates thyroid gland to release thyroid hormone.
Describe the involvement of the mammary gland in the endocrine system.
Prolactin (PRL) acts on mammary glands to stimulate milk production.
Describe the involvement of the gonads in the endocrine system.
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) act on gonads (testes and ovaries) to stimulate development of gametes (sperm and oocyte).
Describe the involvement of the body tissues in the endocrine system.
Growth hormone (GH) acts on all body tissues, especially cartilage, bone, muscle, and adipose connective tissue to stimulate growth.
Describe the involvement of the adrenal gland in the endocrine system.
Adrenocorticotropic hormone (ACTH) acts on the adrenal cortex you cause release of corticosteroids.
Where is the thyroid located?
- Anterior to trachea
- Inferior to thyroid cartilage of larynx
What is the shape of the thyroid?
Butterfly
What does the thyroid produce and release?
Thyroid hormone
What does the thyroid hormone do?
Increased metabolic rate and results in:
- Increased protein synthesis (especially in neurons)
- Increased glucose uptake
- Increased breathing, heart rate and force of contraction
- Increased glycogenolysis, gluconeogenesis and lipolysis
- Decreased glycogenesis and lipogenesis
What are the 3 ways in which endocrine secretion can be triggered?
- Hormonal release
- Humoral agents in the blood (e.g. nutrients, sugars, chemicals)
- Direct neural input
What occurs in hyperthyroidism?
- Upregulates all metabolism
- Tend to be heat intolerant (body temperature is already quite high)
- May lose weight
What type of organs are adrenal glands?
Retroperitoneal organs
Where are adrenal glands located?
At the superior pole of the kidneys
Describe the different parts of the adrenal gland.
Adrenal Medulla (inner core) - Releases epinephrine and norepinephrine in response to sympathetic stimulation
Adrenal Cortex (outer layers) - Releases corticosteroids (e.g. aldosterone which controls fluid/electrolyte balance, cortisol, corticosterone and androgens)