SCIT 1408 Applied Human Anatomy and Physiology II - Lymphatic Chapter 20

8/18/2019 SCIT 1408 Applied Human Anatomy and Physiology II - Lymphatic Chapter 20

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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Lymphatic System: Overview

3 Parts to Lymphatic System

1. Lymphatic vessels – passive, one way return; has

valves; green on models

2. Lymphoid tissues and organs

3. Lymph – interstitial fluid in lymphatic vessels

eturns interstitial fluid and lea!ed plasma

proteins "ac! to the "lood


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Lymphatic System: Overview: Vessels & nodes

Figure 20.2a

## green area drained "y rt

lymphatic duct

##rest of "ody drained "ythoracic duct

arising from cisterna chyli

$ransports cancercells, inflammatory

products;

pathogens;edema if

"loc!ed; immo"ili%elocal infections


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Lymphatic System: Overview: Collects !issue "uice#

Figure 20.$a


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Lymphatic Capillaries: One %ay inivalves

Figure 20.$'

&i

gger than cardiovessels; more permea"le


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Lymphoid Cells

Lymphocytes – immune responders

$ cells

& cells plasma cells

'acrophages, 'onocytes – phagocytes; antigen processing

(endritic cells) phagocytes

ecticular cells) ma!e up stroma structure of

lymphoid organs


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Lymphoid !issue

eticular connective tissue

Lymphoid structures are site of many macrophages * huge

num"ers of lymphocytes that proliferate within tissue

'ay "e (iffuse or in +ollicles

(iffuse lymphatic tissue – scattered; in all organs

Lymphatic follicles nodules- – solid, spherical "odies

consisting of tightly pac!ed reticular elements and cells

erminal center composed of dendritic and & cells

+ound in isolation and as part of larger lymphoid organs


7/20Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20.(a

Lymph )odes

Principal lymphoid organs of the "ody

/lusters along lymphatic vessels

0ear the "ody surface

nguinal

4illary

/ervical Sentenil node- 1st node in lymphatic path to

receive lymph- from cancerous area


8/20Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Lymph )odes

$wo "asic functions

+iltration – macrophages destroy microorganisms

and de"ris

mmune system activation – monitor for antigensand mount an attac! against them

5nlargement due to lymphocyte proliferation



Structure o* a Lymph )ode

Figure 20.(a+ '



Other Lymphoid Organs

Figure 20.,



Spleen

Largest lymphoid organ

left side of the a"dominal cavity "eneath the diaphragm

Splenic artery * splenic vein) highly vascular tissue

+unctions

Site of lymphocyte proliferation – splenomegaly

&rea!s down old "lood cells, pathogens;

Stores, releases "rea!down products of 6g"

Stores platelets

6ematopoietic site in fetus



Structure o* the Spleen

Figure 20.-a+ '

+i"rous


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!hymus

&ilo"ed organ)secretes thymosin * thymopoietin

nfants) in the inferior nec!, into the mediastinum

t increases in si%e and is most active during

childhood t stops growing during adolescence and then

gradually atrophies

T cell maturation

n stroma, epithelium secretes hormones

Antigens do not enter; blood thymus barrier


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nternal /natomy o* the !hymus

/orte4

(ensely pac!ed lymphocytes

Scattered macrophages

'edulla +ewer lymphocytes

Hassall’s corpuscles

7horls of !eratini%ed epithelial cells

Site of $ cell "rea!down


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!onsils

Simplest lymphoid organs; form a ring of

lymphatic tissue around the pharyn4

Location

Palatine tonsils – either side of the posterior end ofthe oral cavity

Lingual tonsils – lie at the "ase of the tongue

Pharyngeal tonsil – posterior wall of thenasopharyn4

$u"al tonsils – surround the openings of theauditory tu"es into the pharyn4


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!onsils

Lymphoid tissue of tonsils contains follicles with

germinal centers

$onsil masses are not fully encapsulated

5pithelial tissue overlying tonsil massesinvaginates, forming "lind)ended crypts

/rypts trap and destroy "acteria and particulate

matter – ma!e memory cells


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/ggregates o* Lymphoid Follicles

Peyer8s patches – isolated clusters of lymphoid

tissue, similar to tonsils

+ound in the wall of the distal portion of the smallintestine

Similar structures are found in the appendi4

Peyer8s patches and the appendi4

(estroy "acteria, preventing them from "reachingthe intestinal wall

enerate 9memory: lymphocytes for long)termimmunity


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/L!

'L$ – mucosa)associated lymphatic tissue

Peyer8s patches, tonsils, and the appendi4

digestive tract-

Lymphoid nodules in the walls of the "ronchi

respiratory tract-

'L$ protects the digestive and respiratory

systems from foreign matter these areas are open

to e4terior-


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evelopmental /spects

&eginnings of the lymphatic vessels and main

clusters of lymph nodes are apparent "y the fifthwee! of em"ryonic development

$hese arise from the "udding of lymph sacs from

developing veins

Lymphatic organs e4cept the thymus- arise from

mesoderm

$hymus – from endoderm


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evelopmental /spects

$he thymus endodermal origin- forms as an

outgrowth of the pharyn4

54cept for the spleen and tonsils, lymphoid organs

are poorly developed at "irth

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SCIT 1408 Applied Human Anatomy and Physiology II - Lymphatic Chapter 20