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Yr 3 Sem 1 > Week 5 > Flashcards

Week 5 Flashcards

1
Q

What are the three components of the lymphatic system?

A

Lymphatic vessels
Lymph
Lymphoid tissues & organs

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2
Q

What are the key functions of the lymphatic system?

A

Circulatory function
Returns fluid that has leaked from the vascular system to the blood

Transport of nutrients, hormones, wastes

Immunity
Lymphocytes housed within lymphoid organs are activated by immune responses

Some lymphoid organs also contain macrophages, which engulf foreign material

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3
Q

What are the lymphatic vessels?

A

An elaborate network of drainage vessels that transport protein-rich interstitial fluid back to the bloodstream

Lymphatic capillaries drain the interstitial spaces of most tissues

When the interstitial fluid enters these vessels, it is called lymph

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4
Q

What is the flow of lymph?

A

Lymphatic capillaries –>lymphatic collecting vessels –>lymphatic trunks –>lymphatic ducts

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5
Q

What are lymphatic collecting vessels?

A

Thin-walled vessels that drain lymphatic capillaries
Possess numerous valves (beaded appearance)

In general, superficial lymphatic vessels (those in the skin and subcutaneous tissues) follow veins and eventually drain into deep lymphatic vessels

Deep lymphatic vessels follow arteries

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6
Q

What are lymphatic trunks?

A

Are formed by large collecting vessels

Named for the regions that they drain

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7
Q

Which lymphatic ducts drain into the thoracic duct or Rt lymphatic duct near the junction of subclavian and int. jugular veins?

A 
Jugular trunks (x2) 
Subclavian trunks (x2)
Bronchomediastinal trunks (x2)
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8
Q

Which lymphatic trunks drain into the cisterna chyli?

A 
Lumbar trunks (x2) 
Intestinal trunk (x1)
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9
Q

What is the thoracic duct?

A

Major vessel of the lymphatic system

38 - 45 cm long, 3-5 mm in diameter

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10
Q

What is the pathway of the thoracic duct?

A

Formed by the convergence of the lumbar & intestinal trunks (anterior to L1/2 vertebrae)

In 50% of people, it begins as an enlarged sac, the cisterna chyli
Cisterna (L. ‘box’), chyli (Gr. ‘juice’)

Ascends through the aortic hiatus into the posterior mediastinum

Enters the venous system at the junction of the Lt internal jugular and Lt subclavian veins

Receives lymph from the Lt jugular, subclavian & bronchomediastinal trunk before entering junction

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11
Q

What is the right lymphatic duct?

A

~ 1.25 cm long

Drains Rt upper limb, Rt side of head and thorax

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12
Q

What is the pathway of the right lymphatic duct?

A

Formed by lymphatic trunks draining the right upper quadrant of the body:
Rt jugular, subclavian & bronchomediastinal trunks

Enters the venous system at the junction of the Rt internal jugular and Rt subclavian veins

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13
Q

What does the lymphatic system rely on to prevent back flow?

A

Lymphatic system lacks a pump

Relies on valves to prevent backflow

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14
Q

What are the factors affecting lymphatic flow?

A

Rhythmic contraction of lymphatic vessels (smooth m.) & pulsations of nearby arteries

Intermittent pressure on lymphatic vessels
e.g. skeletal m. contraction, movement of viscera

Pressure changes in the thorax during respiration

Flow is almost negligible in an immobile limb
e.g. swelling of feet after a long plane trip

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15
Q

What are the 3 lymphoid cells?

A

Consist of lymphocytes, auxiliary immune cells and supporting cells

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16
Q

What are lymphocytes?

A

T cells: cellular adaptive immunity
~75% circulating lymphocytes

Subtypes: cytotoxic, helper, regulatory T cells

B cells: humoral adaptive immunity
Subtypes: plasma, memory cells

Natural Killer cells: innate (nonspecific) immunity
Induce apoptosis of virus- or cancer-infected cells

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17
Q

What are auxiliary immune cells?

A

MACROPHAGES
Widely distributed throughout lymphoid organs

Functions include:
Phagocytosis
Enhancement of inflammatory response
Presentation of antigens to T cells

DENDRITIC CELLS
Mobile, antigen-presenting cells

Possess wispy cellular extensions for antigen capture & phagocytosis

Migrate to lymph nodes and present antigens to naïve lymphocytes (initiates adaptive immune response

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18
Q

What are supporting cells?

A

Reticular cells: fibroblast-like cells that produce a connective tissue stroma (L. ‘bed covering’) for lymphoid tissues and organs

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19
Q

What is the function of lymphoid tissue? (2)

A

Proliferation site for lymphocytes

Surveillance point for lymphocytes & macrophages

20
Q

What are the types of lymphoid tissue? (2)

A

Diffuse lymphoid tissue
Loose arrangement of lymphoid cells & reticular fibres

Occur in most organs of the body
e.g. lamina propria of the GIT

Lymphoid follicles
Solid, spherical bodies consisting of tightly packed lymphoid cells & reticular fibres
Have germinal centres of proliferating B lymphocytes

Form part of lymphoid organs

21
Q

What are primary lymphoid organs?

A

Sites of B & T cell maturation

Red bone marrow, thymus

22
Q

What are secondary lymphoid organs?

A

Where mature lymphocytes first encounter their antigens and become activated

Lymph nodes*, spleen, tonsils, appendix, intestinal follicles (Peyer’s patches)

*Only lymph nodes filter the lymph, other lymphoid organs possess drainage but lack afferent lymphatics

23
Q

What are lymph nodes?

A

Widely distributed secondary lymphoid organs, clustered along lymphatic vessels

Vary in size from a pin-head to an olive (and bigger during pathology)

24
Q

What is the gross structure of lymph nodes?

A

Dense fibrous capsule
Compartmentalised by trabeculae
Stroma of reticular connective tissue

25
What are the functions of lymph nodes?
House lymphocytes AND macrophages Site of immune system activation Filtering of lymph (microorganisms, debris)
26
What is the histology of lymph nodes? (3)
CORTEX Germinal centres of proliferating B cells T cells in transit (circulating in lymph & blood) Numerous dendritic cells MEDULLA Medullary cords – thin inward extensions from the cortex, contain numerous B & T cells LYMPH SINUSES Lymphatic channels crossed by a network of reticular fibres (macrophages reside on these fibres) Subcapsular sinus, medullary sinus
27
What is nodal circulation?
Lymph flows into the node through numerous afferent lymph vessels (convex side) Lymph moves through the subcapsular sinus towards the medulla Flow occurs through medullary sinuses Exits via efferent lymph vessels Located at hilum (indented region on concave side)
28
What is the gross structure of the spleen?
Largest lymphoid organ, roughly the size of a clenched fist Dark red, highly vascular, ovoid organ Enclosed by a thin (easily ruptured) capsule of fibroelastic connective tissue + smooth m. cells Trabeculae extend inward to the interior to form a supporting framework Intraperitoneal: surrounded by visceral peritoneum except the hilum (entry of splenic artery & exit of splenic vein)
29
What are the surfaces of the spleen?
Diaphragmatic surface: outer, convex Visceral surface: inner, concave Impressions from stomach, kidney, colon, pancreas
30
What are the peritoneal ligaments of the spleen?
The gastrosplenic & splenorenal ligaments attach to the hilum of the spleen These ligaments contain the splenic vessels
31
What is the location of the spleen?
Lt Hypochrondriac region, LUQ behind stomach Roughly deep to Ribs 9 - 11 ribs (separated by diaphragm) Rests on the Lt colic flexure
32
What is the function of the spleen? (5)
Immunity: site for lymphocyte proliferation, surveillance & response Blood filter: macrophages remove debris, foreign matter Reservoir: blood, platelets, monocytes When needed, spleen contracts and releases these substances into the circulation Recycles: by-products of RBC breakdown e.g. iron Erythropoiesis (foetus)
33
What is the histology of the spleen? (2 main components)
``` Two main components: islands of white pulp in a sea of red pulp (L. ‘flesh’) Friable texture (easily crumbled) ``` White pulp: site of immune functions Mostly lymphocytes suspended on reticular fibres Red pulp: where senescent RBC and bloodborne pathogens are destroyed Huge numbers of erythrocytes and the macrophages that engulf them
34
What is the arterial supply to the spleen?
Splenic a.: largest branch of the celiac trunk Splenic a. runs a tortuous course along the superior border of the pancreas At the splenic hilum, it divides into a number of branches (~5) before entering
35
What is the venous drainage of the spleen?
Splenic v., formed by several tributaries emerging from the hilum (and joined by IMV) Runs posteriorly to the tail and body of the pancreas for most of its course Unites with SMV posterior to the neck of the pancreas to form the portal v.
36
What is the lymphatic drainage of the spleen?
Lymph nodes in the splenic hilum Drain to the pancreaticosplenic lymph nodes -->celiac nodes -->intestinal trunk
37
What is the nerve supply of the spleen?
Sympathetic: abdominopelvic splanchnic nerves via the celiac ganglion (T6-T10) *Stimulate contraction of the spleen. Parasympathetic – CNX Vagus
38
Discuss a splenectomy (Why is it performed?) (What replaces the function of the spleen?)
The spleen is one of the most easily and frequently injured abdominal organs Rupture can lead to extensive haemorrhaging (highly vascular organ) Splenectomy (full or partial) may be performed to prevent haemorrhagic shock Liver & red bone marrow can replace the functions of the spleen In children <12 years, the spleen can regenerate if partially removed
39
What is a microbiome?
a collection of microbial genomes
40
What is a microbiota?
a collection of microbes
41
What is the human microbiome?
Is an integral part of the human body Varies according to body site: GIT, vagina, urethra, skin Is plastic and influenced by environmental exposures 90% of the cells in and on the body are microbial
42
# Define these key terms: Commensal Probiotic Pathogen Dysbiosis
Commensal: a colonising organism that is neither beneficial nor detrimental Probiotic: an organism that elicits health benefits to the host Pathogen: an organism that is detrimental to the host or causes disease Dysbiosis: loss of balance within a microbial community
43
What can dysbiosis cause?
Can shift a healthy microbiome to a disease-associated state Disease can arise when: Microbiome diversity increases at sites that normally have restricted diversity Or when there is reduced diversity at body sites that usually have great diversity BACTERIAL SIGNALS & COMPOUNDS Can modulate signalling pathways (e.g. metabolism), immune cell responses and change host gene expression
44
Dysbiosis and disease (GIT microbiome & vaginal and urethral microbiome)
Can be local or systemic in nature GIT microbiome Dental caries Peptic ulceration, oesophageal & gastric carcinoma Obesity Ulcerative colitis, Crohn’s disease* Irritable bowel syndrome Sleep, mood, stress disorders** Vaginal & urethral microbiome Bacterial vaginosis Recurrent UTIs Susceptibility to infection during pregnancy Pre-term birth Implications for vaginal vs. C-section delivery
45
What is disease management for the human microbe?
Microbial manipulation strategies Human nutrition Antibiotics Microbial supplementation (probiotics)

Yr 3 Sem 1 (7 decks)

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