LYMPHATIC SYSTEM

1
LYMPHATIC SYSTEM

• I. Early origin - first appears in fish
• A. Fish -
• Subvertebral ducts empty into anterior cardinal
  veins
• Lateral ducts emptying into iliac veinThese are
  retained in all tetrapods (embryonically). No
  lymph return mechanisms - lymph simply returns
  via venous capillaries

2

• B. Early tetrapods - 2 anterior and 2 posterior
  ducts
• Capillary pressure increases interstitial
  filtrate and venous capillaries could not absorb
  increased volume

3

• C. Frogs and Salamanders
• FrogsLymph collects in lymph sinuses
• SalamandersIncreased number of vessels and
  smaller sinuses Lymph hearts (4 in frog) and
  speed flow of lymph into venous system

4
D. Reptiles - general pattern retained but
anterior hearts are lost.E. Birds - no lymph
hearts, presence of valves in lymph vessels -
body movements move lymph.
5
F. Mammals - posterior iliac openings lost.
nearly all vessels drain into large thoracic duct
which empties into external jugular
6
FETAL CIRCULATION
Ductus arteriosus
I. General Circulation
Fossa ovale
Ductus venosus
Umbilical vein
Umbilical Artery
7
II. Changes at BirthA. Ductus arteriosus -
closes - arterial ligamentB. Interatrial valve
- closes (foramen ovalis by change in pressure -
scar fossa ovale)
8
C. Umbilical artery - severed and converted to
lateral umbilical ligament on border of urinary
bladderD. Umbilical vein - round ligament of
liverE. Ductus venosus - ligamentum venosum