Lecture 17: The Endocrine And Lymphatic System Flashcards Preview

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Flashcards in Lecture 17: The Endocrine And Lymphatic System Deck (28):

What are the 2 main classes of hormones?

1. Amino-acid based hormones eg amines, thyroxine, peptides, proteins
2. Steroids
-synthesised from cholesterol
-gonadal and adrenocortical hormones

Target cells must have specific receptors to which the hormones bind


The pituitary gland and hypothalamus
What are the 2 major lobes of the pituitary?

Pituitary gland has 2 major lobes:
1. Posterior pituitary (lobe):
-nerve fibres
2. Anterior pituitary (lobe):
-glandular tissue


Hormonal stimuli
Hormones can stimulate other endocrine organs to release their hormones. Give example

Hypothalmic hormones stimulate the release of most anterior pituitary hormones
Anterior pituitary hormones stimulate targets to secrete more hormones from target endocrine organs


What is the relationship between the posterior pituitary and the hypothalamus?

1) hypothalmic neurons synthesize oxytocin and ADH
2) oxytocin and ADH are transported along the hypothalmic-hypophyseal tract to the posterior pituitary
3) oxytocin and ADH are stored in axon terminals in the posterior pituitary
4) oxytocin and ADH are released into the blood when hypothalmic neurons fire


Pituitary-hypothalmic relationships
Ie between postior lobe and anterior lobe

Posterior lobe:
-extension of hypothalmic neural tissue
-nuclei of the hypothalamus synthesize the neurohormones oxytocin and ADH
-neurohormones are transported r the posterior pituitary

Anterior lobe:
-it is glandular
-hypophyseal portal system
-carries releasing and inhibiting hormones


Relationship between the anterior pituitary and the hypothalamus

1) When appropriately stimulated, hypothalmic neurons secrete releasing and inhibiting hormones into the primary capillary plexus.
2) hypothalmic hormones travel through the portal veins to the anterior pituitary where they stimulate or inhibit release if hormones from anterior pituitary.
3) anterior pituitary hormones are secreted into the secondary capillary plexus


List the anterior pituitary hormones
Go Ahead Fuck The Pregnant Lady

Growth hormone
Thyroid-stimulating hormone
Adrencorticotropic hormone
Follicle stimulating hormones
Luteinizing hormone

All are proteins
TSH, ACTH, FSH, LH are all tropic hormones (regulate secretory action of other endocrine glands)


What is the function of the growth hormone?
What happens if it hyper secretes or hyposecretes

-Stimulates most cells, but targets bone and skeletal muscle
-promotes protein synthesis and encourages use of fats for fuel
The direct action of GH is to stimulate liver, skeletal muscles bone, and cartilage to produce insulin-like growth factors

-in children results in gigantism
-in adults results in acromegaly
-in children results in pituitary dwarfism


What is the function of thyroid-stimulating hormone
How is it regulated

Stimulates the normal development and secretory activity of the thyroid
Regulation of TSH
-inhibited by rising blood levels of thyroid hormones that act on the pituitary and hypothalamus


What is the function of adrenocorticotropic hormone

Function of prolactin

Adrenocorticotropic hormone:
-stimulates the adrenal cortex to release corticosteroids

-stimulates milk production
-blood levels rise towards end of pregnancy
-suckling stimulates PRL release and promotes continues milk production



-Follicle-stimulating hormone (FSH) and luteinizing hormone
-FSH stimulates gamete (egg or sperm) production
-LH promotes production of gonadal hormones


What are the 3 parts the lymphatic system consists of?
What are the functions of the lymphatic system?

1. A network of lymphatic vessels
2. Lymph (fluid)
3. Lymph nodes

Returns interstitial fluid and leaked plasma proteins back to the blood
-once interstitial fluid enters lymphatics, it is called lymph
Together with lymphoid organs and tissues, provide the structural basis of the immune system


What are the lymphatic vessels in the system?

It's a one one system, lymph flows towards the heart
Lymph vessels (lymphatics) include:
-lymphatic capillaries (smallest)
-lymphatic collecting vessels (medium sized)
-lymphatic trunk and ducts (largest)


Describe the lymphatic capillaries

Similar to blood capillaries except:
-very permeable (take up cell debris, pathogens, and cancer cells)
-endothelial cells overlap to form one-way mini valves, and are anchored by collagen filaments, preventing collapse of capillaries
None in the CNS
Lacteals: specialised lymph capillaries present in intestinal mucosa
-absorb digested fat and deliver fatty lymph (chyle) to the blood


Describe the lymphatic collecting vessels

Similar to veins, except
-have thinner walls, with more internal valves
Trunks are formed by the union of the largest collecting ducts
-paired lumbar
-paired subclavian
-paired jugular trunks
-a single intestinal trunk


What are lymphatic ducts, what do they do?

Lymph is delivered into one of 2 large ducts
-right lymphatic ducts drains the right upper arm and the right side if the head and thorax
-thoracic duct arises from cisterna chyli and drains the rest of the body
Each empties lymph into venous circulation at the junction of the internal jugular and subclavian veins on its own side of the body
Lymph is propelled by:
-pulsation of nearby arteries
-contraction of smooth muscle in the walls of the lymphatics


What are the lymphoid cells of the body?

Aka lymphocytes: warriors of immune system
-macrophages phagocytise foreign substances and help activate T cells
Two main varieties
-T cells
-B cells
T cells and B cells protect against antigens
T cells
-manage the immune response
-attack and destroy foreign cells
B cells
-produce plasma cells, which secrete antibodies


What is the function of the lymphoid tissue?

-Houses and provides a proliferation site for lymphocytes
-furnishes a surveillance vantage point
Two main types:
1. Diffuse lymphatic tissue
-diffuse lymphatic tissue comprises scattered reticular tissue elements in every body organ
-larger collections in the lamina propria if mucous membranes and lymphoid organs

2. Lymphatic follicles
-lymphatic follicles (nodules) are solid, spherical oldies of tightly packed reticular elements


What are lymph nodes what is their function?

-principle lymphoid organs of the body
-embedded in connective tissue, in clusters along lymphatic vessels
-near the body surface in inguinal, axillary and cervical regions of the body
1-filter lymph-macrophages destroy microorganisms and debris
2- immune system- lymphocytes are activates and mount an attack against antigens


Describe the structure of a lymph node

-Bean shaped with an external fibrous capsule
-Two histology ally distinct regions
Cortex- which contains follicles with germinal centres
Medulla- lymph sinuses contain macrophages
T cells circulate continuously among the blood, lymph nodes, and lymphatic stream


Circulation of the lymph nodes

-enters via afferent lymphatic vessels
-travels through large subscapular sinus and smaller sinuses
-exits the node at the hilum via efferent vessels



-Largest lymphoid organ
-served by splenic artery and vein
-site of lymphocyte proliferation and immune surveillance and response
-cleanses the blood of aged cells and platelets and debris

-stores breakdown products of RBC's eg iron
-site of fetal erythrocyte production (normally stops after birth)
-has a fibrous capsule and trabeculae
-contains lymphocytes, macrophages, and huge numbers if erythrocytes.


Describe the structure of the spleen

Has 2 distinct areas
-White pulp around central arteries
-red pulp in venous sinuses and splenic cords
(Rich in macrophages for disposal of worn-out RBS's and blood borne pathogens


What is the thymus and what is its function?

Size with age:
-In infants, it is found in the inferior neck and extends info the mediastinum, where it is partially overlies the heart
-increase in size and is most active during childhood
-stops growing during adolescence and then gradually atrophies
Contains densely packed lymphocytes and scattered macrophages
Differs from other lymphoid organs in important ways
-it functions strictly in T lymphocyte maturation
-it doesn't directly fight antigens



Simplest lymphoid organs
Form a ring of lymphatic tissue around the pharynx
-palatine tonsils- at posterior end of the oral cavity
-lingual tonsils- grouped at base of tinge and
-pharyngeal tonsils- in posterior wall of the nasopharynx
Epithelial tissue overlying tonsil masses invagination, forming tonsillar crypts
Crypts trap and destroy bacteria and particulate matter


Mucosa- associated lymphatic tissue

-Peyers patches, tonsils, and the appendix (digestive tract)
-Lymphoid nodules in the walls of the bronchi (respiratory tract)
Protects the digestive and respiratory systems from foreign matter
Peyers patches
-in the wall of the distal portion of the small intestine
-similar structures are also found in the appendix
-destroy bacteria, preventing them from breaching the intestinal wall
-generate "memory" lymphocytes


Developmental aspects

Lymphatic organs arise from mesoderm (except the thymus: endoderm)
Except for the spleen and tonsils, lymphoid organs are poorly developed at birth.


List the endocrine structures of the body

Pituitary gland
Thyroid gland
Parathyroid gland
Adrenal glands