Lymphatic and Endocrine Systems Flashcards
1
Q
3 main lines of defence of lymphoid/immune system
A
- protective surface: skin, mucous surfaces, acid secretion
- non-specific cellular response: phagocytic cells, inflammation, anti-viral agents
- specific immune response: antigen recognition
2
Q
2 types of immune response
A
- humoral response: antibody production (B cells)
- cellular response: T cells
3
Q
Lymphoid organs
A
- thymus
- lymph nodes
- spleen
- bone marrow
4
Q
Mucosa-associated lymphoid tissue (MALT)
A
- located in walls of gastrointestinal, respiratory and urogenital tracts
5
Q
Gut-associated lymphoid tissue (GALT)
A
- palatine, lingual and pharyngeal tonsils
- mucosal nodules in oesophagus
- Peyer’s patches in small intestine
- Lymphoid aggregates in large intestine and appendix
- lymphocytes and plasma cells in lamina propria small and large intestines
6
Q
Bronchus-associated lymphoid tissue (BALT)
A
- lymphoid follicles associated with mucosa of bronchi
7
Q
Thymus
A
- major activity in childhood
- decrease size and activity in puberty
- infiltrated by lymphocytes during development
- production of immunocompetent T cells from T lymphocytes
8
Q
Lymph nodes
A
- encapsulated, highly organised aggregates of lymphocytes
- arranged along vessels of lymph vascular system
- filtration of lymph
- storage/proliferation of B+T lymphocytes
9
Q
Spleen
A
- filter blood as part of immune system
- recycling old RBCs
- storage platelets and WBCs
- helps to fight certain kind of bacteria (pneumonia, meningitis)
10
Q
Other lymphoid aggregates
A
- Tonsils
- Peyer’s patches
- appendix
11
Q
Where do T and B cells emigrate to and from?
A
- from thymus/bone marrow
- to peripheral lymphoid organs as part of adaptive immune system
12
Q
Thymus gland as “training school for T lymphocytes”
A
- lymphocytes move into cortex thymus
- nurse cells surround lymphocytes and from isolated barrier
- nurse cells test developing T cells by exposing to foreign and self antigens
- only those that recognise foreign antigens survive and undergo further training
- possible T cells exposed to many kinds of molecules
- lymphocytes progressively develop into immunocompetent T cells
13
Q
Blood, lymphatics and bone marrow
A
- Little structure or aggregate
- Cells in transport
- Stained with H&E, Wright’s, Giemsa or Wright-Giemsa stain (combination of Eosin, Azure Blue, Methylene Blue)
14
Q
Reticuloendothelial/ mononuclear phagocyte system
A
- haemopoietic stem cells in bone marrow: tissue specific macrophages
- Kupffer cells: liver
- Microglia cells: brain
- Reticular cells: lymphoid tissues
- Alveolar macrophages: lungs
- Histiocytes: subcutaneous tissue
15
Q
Histology of thymus
A
- Connective tissue capsule
- Connective tissue trabeculae (Blood vessels, adipose cells)
- Lobules with Cortex and Medulla (thymic reticular cells, thymic or Hassal’s corpuscles, adipose cells)
16
Q
Thymic reticular cells
A
- Contain secretory granules containing thymic hormones (thymulin, thymopoietin, thymosin, interleukins,
interferons) - involved in the blood-thymus barrier
- Contact of immature T cells and foreign antigens would cause T cells to die by apoptosis)
17
Q
Thymic/Hassal’s corpuscles
A
- function is unclear, involution by puberty
- found in medulla of human thymus, formed from dysfunctional epithelial reticular cells arranged concentrically
- keratin positive in stain
18
Q
Histology of lymph node
A
- capsule
- perinodal adipose tissue
- trabecula
- subcapsular sinus
- afferent lymphatic vessels
- lymphatic nodules
- hilum (efferent lymphatic vessels, lymphatic artery and vein)
19
Q
Lymphatic nodules (or lobules)
A
- outer cortex: inactivated B cells or follicles. May develop into germinal centre when activated
- inner or paracortex: T cells
- medulla: large blood vessels, medullary sinus and medullary cords (antibody-secreting plasma cells)
20
Q
Lymph flow in lymph node
A
- efferent lymphatics leave lymph node at hilum
- lymph goes into medullary sinus, contains B cells and plasma cells
- lymph flows in deep cortex, dominated by T cells
- flows into outer cortex, contains B cells
- dendritic cells, initiate immune response
- afferent lymphatics carry lymph to node from peripheral tissues
21
Q
Histology of Spleen
A
- capsule
- trabeculae
- white pulp: active immune response
- red pulp: filtration of RBCs
22
Q
White pulp in spleen
A
- lymphoid follicles (rich in B lymphocytes)
- periarteriolar lymphoid sheaths (PALS, rich in T lymphocytes)
23
Q
Red pulp in spleen
A
- sinuses (sinusoids)
- splenic cords
- marginal zone
24
Q
Functions of red pulp
A
- Removal of old red blood cells (iron recycled)
- Storage of red blood cells and lymphocytes
- Produces all types of blood cells (only during foetal life)
25
Endocrine system
- Consists of DUCTLESS GLANDS that secrete HORMONES into blood
system
26
Effects of endocrine system
- regulation of ion content and water balance of internal environment
- immune system regulation
- regulation of blood glucose and other nutrients & energy balance
- Help cope with emergency demands (trauma, stress, extremes of temperature)
- Role in sequential integration of growth & development
- Contribute to basic processes of reproduction including gamete/sperm production, nourishment of embryo/foetus, and delivery of new-born
27
Exocrine glands
- Secrete products onto free surface areas or into ducts, then to body cavities, lumen,
or to body surface.
- e.g. sweat glands, mucous glands, glands producing digestive enzymes
28
Endocrine glands
- Secrete hormones directly into the blood rather than through a duct
- e.g. pituitary glands, ovaries, testes
29
Principal endocrine glands
- Pituitary (neuroendocrine organ)
- Thyroid
- Parathyroid
- Adrenal
- Pineal
- Thymus
30
Other organs with endocrine tissue
- Hypothalamus (neuroendocrine organ)
- Pancreas
- Ovaries
- Testis
- Kidney
- Stomach
- Small intestine
- Placenta
- Liver
31
Amines (hormones)
- simplest hormone molecules, produced from an amino acid. Water soluble
- thyroxine produced in thyroid gland
- epinephrine produced in adrenal gland (medulla)
32
Proteins and peptides (hormones)
- consist of chains of amino acids, also water soluble
- Oxytocin in hypothalamus
- Insulin in pancreas
- Pituitary hormones (GH, LH etc) in anterior pituitary
- calcitonin in thyroid
- parathyroid hormone in parathyroid gland
33
Steroids (hormones)
- Derived from cholesterol, Lipid soluble
- aldosterone in adrenal cortex
- testosterone in testis
- oestrogen/progesterone in ovaries
34
Pituitary
- situated in sella turcica of sphenoid bone, attached by a stalk to the floor of 3rd ventricle of brain
- adenohypophysis (anterior pituitary): pars distalis, pars intermedia, pars tuberalis
- neurohypophysis (posterior pituitary): pars nervosa, infundibulum
35
Adenohypophysis
- pars anterior: largest of organ
- secretory cycle: chromophobes give rise to chromophils, return to chromophobe upon secretion
- alpha and beta cells produce all hormones of anterior lobe and release them into bloodstream
- pars tuberalis: vascular, consists of solid cords of non-granular epithelial cells
- pars intermedia: small, much less vascular than pars anterior, cells usually clear
36
Pars nervosa (neurohypophysis)
- Functional part are groups of axons of neurosecretory cells that are mainly originating from hypothalamus
- Also present are blood vessels and connective tissue
- Herring bodies are structures found in the posterior pituitary, represent terminal end of axons from hypothalamus, and hormones are temporarily stored in these locations, they're neurosecretory terminals
- Pituicytes are neuroglia type cells - supporting not secretory
37
Infundibulum (neurohypophysis)
- hollow stalk which connects the hypothalamus and the posterior pituitary gland
38
Variation in structure of anterior/posterior lobes
- cleft in young
| - isolated cysts in adult
39
Variation in structure of lobes in pregnancy
- Anterior lobe larger (135%) due to oestrogen-stimulated hyperplasia and hypertrophy of prolactin cells (to ensure lactation)
40
Variation in structure of lobes in puberty
- growth spurt is associated with increase in pars anterior due to great increase of alpha cells producing growth hormone
41
Hypopituitarism
- decreased (hypo) secretion of one or more of the eight hormones normally produced by pituitary gland
(e. g. pituitary dwarfism - decreased production of GH)
42
Hyperpituitarism
- increased (hyper) secretion of one or more of the 8 hormones normally produced by pituitary gland (e.g. pituitary adenoma
producing growth hormone)
- Induces gigantism if the condition develops before union of epiphyses of
long bones (in childhood).
- Induces acromegaly if the condition develops after union, when bony overgrowth causing somatic enlargement specifically in the extremities and face (in adult)
43
Acidophils
- somatotropes (growth hormone)
| - Lactrotropes (prolactin)
44
Basophils
- Thyrotropes (thyroid stimulating hormone)
- Gonadotropes (luteinizing hormone or follicle-stimulating hormone)
- Corticotropes (adenocorticotrophic hormone)
45
Thyroid gland
- located below larynx, in front of Trachea
- 2 lobes connected by mass of tissue - Isthmus
- Very rich blood supply, can deliver high levels of hormone quickly
- Gland filled with microscopical sacs - Follicles
- produces 3 hormones: T3, T4 and Calcitonin.
- Consists of Follicular cells and Parafollicular cells (or C cells)
46
Follicular cells
- Thyroxine (T4)
- Tri-iodothyrine (T3)
- Hormones that regulate base metabolic rate and influence growth/maturation of nervous tissue
47
Parafollicular cells
- Calcitonin
- Regulates blood calcium levels in conjunction with Parathyroid hormone
- Recognised by extensive unstained cytoplasm
48
Thyroid follicles
- lined by simple cuboidal epithelium (= follicular cells) filled with glycoprotein complex called Thyroglobulin or Thyroid Colloid (=precursors to thyroid
hormones T3 and T4)
49
Certinism (thyroid gland disorder)
- Lack of thyroxine from birth or before birth
- Could be from lack of thyroid gland or lack of iodine in mother
- Irreparable mental defects
- Stunted growth
- Reduced growth and function of many organs
50
Myxedema (thyroid gland disorder)
- Occurs because of severe hypothyroidism that is not diagnosed or is not treated successfully.
- a person may experience symptoms such as drowsiness, confusion and hypothermia as well as changes to the skin
51
Goitre (thyroid gland disorder)
- a swelling of the neck resulting from enlargement of the thyroid gland
- due to lack of iodine in diet, over- or underproduction of
thyroid hormones or nodules in gland itself
- In most cases, the swelling is small and does not cause any
symptoms
52
Parathyroid
- Small oval shaped gland, closely associated with thyroid gland
- Principle role is regulation of serum calcium and phosphate levels via parathyroid hormone
53
Chief (principal) cells in parathyroid
- Most abundant, secrete parathyroid hormone.
| - Prominent nucleus, little cytoplasm, varies staining intensities depending on degree of secretory activity
54
Oxyphil cells in parathyroid
- produce additional autocrine and paracrine factors, function and secretions not fully known
- Larger, less numerous than chief cells, small densely stained nuclei, strongly eosinophilic cytoplasm
55
Tetany (parathyroid gland disorder)
- calcium deficiency due to hypoparathyroidism
- Causes neurones to depolarise without usual stimulus, leading to increased nervous impulses causing twitches, spasms and convulsions.
56
Osteitis fibrosa cystica (parathyroid gland disorder)
- blood phosphate lowered, blood calcium increased, produces pathological deposits of calcium in several
organs (kidneys/arteries)
- Condition arises from
hyperparathyroidism
- Characterised by increased activity and number of osteoclasts, multiple bone cavities. Bones less resistant, and prone to fractures
57
Adrenal
- Small flattened glands closely linked to upper pole of each kidney
- 2 distinct areas: adrenal cortex and adrenal medulla
58
Adrenal cortex
- secretes a variety of steroid hormones linked to cholesterol
- Mineralocorticoids: electrolyte/fluid haemostasis
- Glucocorticoids: carbohydrate, protein, lipid metabolism
- Sex hormones: to supplement gonadal production
59
Adrenal medulla
- highly specialised adjunct to sympathetic nervous system
| - Secretes the Catecholamines Adrenalin (Epinephrine) and Noradrenalin (Norepinephrine)
60
3 zones of adrenal cortex
- zona glomerulosa: cells arranged in irregular ovoid clumps. Round, strongly stained nuclei, sparse cytoplasm, abundant smooth ER and mitochondria with triglyceride droplets. Secretes mineralocorticoid hormones
- zona fasciculata: intermediate but broadest zone. Large secretory cells, abundant cytoplasm, secretes glucocorticoid hormones
- zona reticularis: thin innermost layer, may be responsible for secretion of small amounts of sex hormone
61
What does adrenal medulla contain?
- small closely packed clumps of secretory cells with large granular nuclei, strongly basophilic cytoplasm
- chromaffin cells secretes catecholamine hormones adrenalin and noradrenalin.
62
Adrenal gland disorders
- Aldosteronism: due to over secretion of aldosterone
- Hypertension: largely due to increased sodium and decreased potassium
- Addison's disease: due to increased potassium and decreased sodium, leading
to low blood pressure
- Cushing’s syndrome: an increase in the production of glucocorticoids such as Cortisol
63
Pineal gland
- Small organ connected by short stalk to brain, containing nerve fibres that communicate
with the hypothalamus
- Plays role in biological cycles (circadian rhythms, i.e. sleep and wake cycles)
- Produces melatonin from the precursor serotonin. Melatonin secretion is inhibited by light and triggered by darkness.
- largest at infancy and early childhood, involutes rapidly at puberty
- Melatonin suppresses production of Gonadotrophin Releasing Hormone by the
hypothalamus, suppressing pituitary gonadotrophin secretion/activation of gonadal
growth and hormone secretion.
- controls the onset of puberty
64
Cells of pineal gland
- Pineal Chief cells (Pinealocytes): modified neurones
| - Neuroglial cells: similar to astrocytes
65
Ageing in pineal gland
- Appearance of basophylic extracellular bodies called Corpora Arenacea. Also referred to as Pineal Sand or Brain Sand
- calcified structures in the pineal gland.
- can be seen on X rays of skull and are useful guide for location of pathological conditions.
66
Pancreas
- Major exocrine and endocrine gland
- Clumps of endocrine tissue form Islets of Langerhans
- Clumps of secretory cells supported by fine reticular network containing numerous fenestrated capillaries
- Small cells with poorly stained cytoplasm, surrounded by strongly stained pancreatic tissue (greater amounts of RER in exocrine cells which secrete protein)
67
3 principal cell types in pancreas
- Alpha cells which secrete Glucagon
- Beta cells which secrete Insulin
- Delta cells which secrete Somatostatin
- All indistinguishable with H&E, require specialised tinctorial stains or immunohistochemistry
to identify individually
68
Insulin-dependent type 1 diabetes (pancreas gland disorder)
- partial or total destruction of Beta cells due to autoimmune disease (individual susceptibility controlled by several genes)
69
Insulin-dependent type 2 diabetes (pancreas gland disorder)
- occurs later in life, frequently associated with obesity
70
Islet cell tumours (pancreas gland disorder)
- may produce insulin, glucagon, somatostatin, and pancreatic polypeptide
- Some produce 2 or more of these hormones simultaneously, giving complex clinical symptoms
71
Enteroendocrine cells
- Intestines/Digestive Tract:
- Found in gastric glands throughout GIT
- Variety of hormones produced (gastrin, secretin, gastric inhibitory polypeptide, glucagon-like polypeptide, cholecystokinin, somatostatin, motilin, serotonin substance P, vasoactive intestinal polypeptide)
72
Carcinoids or carcinoid tumour (enteroendocrine cell disorder)
- slow-growing neuroendocrine tumour
- produce several vasoactive substances, mainly serotonin
- Overproduction of serotonin increase gut motility, but high levels are related to mucosal vasoconstriction and damage
