Lecture 17: The Endocrine And Lymphatic System Flashcards
What are the 2 main classes of hormones?
- Amino-acid based hormones eg amines, thyroxine, peptides, proteins
- 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:
- Posterior pituitary (lobe):
- nerve fibres - 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 Prolactin
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
Hypersecretion: -in children results in gigantism -in adults results in acromegaly Hyposecretion: -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
Prolactin:
- stimulates milk production
- blood levels rise towards end of pregnancy
- suckling stimulates PRL release and promotes continues milk production
Gonadotropins
- 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?
Parts:
- A network of lymphatic vessels
- Lymph (fluid)
- Lymph nodes
Function:
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
- 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
Functions:
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
Lymph
- enters via afferent lymphatic vessels
- travels through large subscapular sinus and smaller sinuses
- exits the node at the hilum via efferent vessels
Spleen
-Largest lymphoid organ
-served by splenic artery and vein
Functions:
-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
Tonsils
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
MALT
-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
Pineal Hypothalamus Pituitary gland Thyroid gland Parathyroid gland Thymus Adrenal glands Pancreas Ovary Testis
