explanation of anastomosis along with its different types, their clinical and medical significance, components that are in part of anastomosis

2. ANASTOMOSIS

3. INTRODUCTION
• DEFINATION
• TYPES OF ANASTOMOSIS
I. Arterial Anastomosis
A-Actual anastomosis
B- Potential anastomosis
C- End anastomosis or no anastomosis
II. Venous Anastomosis
III. Arterio-venous Anastomosis or Vascular Shunts
A. Preferential thoroughfare channels
B. Simple arteriovenous anastomosis:
C. Complex arterio-venous anastomosis or glomus :

4. ANASTOMOSIS
DEFINITION
ANATOMICALLY
It is a communication between two vessels by
collateral channels.

5. CLINICALLY
It is a communication created by surgical, traumatic
or pathological means between the two normally
distinct spaces or organs, e.g.
(i) Intestinal Anastomosis: An anastomosis between
the two portions of intestinal tract.
(ii)Ureterotubal anastomosis, an anastomosis between
the ureter and uterine tube.

7. TYPES OF ANASTOMOSIS:
There are three types of anastomosis:
I. Arterial Anastomosis
II. Venous Anastomosis
III. Arterio-venous Anastomosis or Vascular Shunts

9. I. ARTERIAL ANASTOMOSIS:
• The anastomosis between various arteries of the body.
• Great importance in medicine and surgery.
It has following SUB-VARIETIES :
(A) ACTUAL ANASTOMOSIS:
It is a communication between arterial trunks of nearly equal size.
Examples:
i) Labial branches of facial artery.
ii) Anterior and posterior intercostal arteries.
iii) Uterine arteries.
iv) Ovarian arteries
v) Gastric arteries
vi) Gastroepiploic arteries
Test: The cut vessel spurts from both ends.

12. (B) POTENTIAL ANASTOMOSIS:
It is a communication established by union of
terminal arterioles.
Examples:
i)Coronary arteries.
ii)Limb arteries in the regions of joints
iii)Cortical arteries of cerebral hemispheres.

13. Significance:
• With gradual occlusion of the artery, the arterioles can dilate sufficiently to
provide adequate nutrition.
•However, if occlusion of main vessel is sudden, then the potential
anastomosis will not be able to dilate sufficiently in order to provide
adequate nourishment.
•As a result of this, the death of the area supplied by the artery will occur
(Necrosis / Infarction).

15. (C) END ANASTOMOSIS OR NO ANASTOMOSIS:
In certain regions of the body, there are arteries,
which have no anastomosis with their neighbouring
vessels. These arteries are, therefore, called as End-
Arteries.
True Example:
Central Artery of the Retina.
Significance:
If an artery of this type is occluded, then the area
supplied by the artery will undergo necrosis
(microscopic death of tissue). That is why the
occlusion of central artery of retina will lead to
blindness.

16. The left ocular fundus as seen with an ophthalmoscope

17. False examples:
Here the communication takes place at capillary level
only and practically results in the formation of
End-Anastomosis, e.g.
i) Central Arteries of the brain.
ii)Arteries of spleen.
iii)Arteries of kidney.
iv)Arteries of liver.
v) Vasa recta of mesenteric arteries.
vi) Metaphyseal arteries of long bones.
vii)Arteries of lung.
Significance:
Interruption of arterial flow will result in necrosis or
infraction or gangrene of the area supplied.

18. II. VENOUS ANASTOMOSIS:
• It is a communication between veins.
• It is much more frequent and highly variable and is
of lesser significance.
Examples:
i)Dorsal venous arch of hand.
ii)Dorsal venous arch of foot.
iii)Anastomosis between cephalic and basalic veins
through median cubital vein.
iv) Azygos vein which connects the inferior vena cava
with the superior vena cava.

20. III. ARTERIO-VENOUS ANASTOMOSIS
OR VASCULAR SHUNTS:
• In many tissues of the body, communication exists
between arterial and venous sides of circulation.
• When these short circuiting channels open then the
blood will pass directly from the arterioles into the
venules and will not pass through the capillaries.
• The reason for their existence and the mechanism of
their control are not understood.

21. The arterio-venous shunts
are divided into three
sub-varieties according to
site, dimensions and
complexity.
A. Preferential
thoroughfare channels:
Grant and Wright (1968
and 1970) have
demonstrated that true
capillaries are also given
out from thoroughfare
channel, which connects
the terminal arteriole and
venules.

22. Characteristics:
I) The caliber is larger than true capillaries.
2) The structure resembles the continuous capillaries
but few smooth muscle cells are present around the
endothelium.
3) The thoroughfare channel and its associated
capillaries form a functional micro-circulatory unit.
Each capillary from the thoroughfare channel is
surrounded by a pre-capillary sphincter at its origin.

23. 4)The size of micro-circulatory unit varies in different
tissues,
e.g.
i)In striated muscle, each thoroughfare channel may
give rise to about 25 true capillaries.
ii)In glandular tissue, only two capillaries are given out
from thoroughfare channel.

24. 5)The form of capillary network also varies with the type of the tissue,
e.g.:
a)The capillary network is rounded or angular at
Following situations:
i) Lungs.
ii) Mucous membranes.
iii) Skin.
b) The capillary network is elongated in:
i) Muscles.
ii)Nerves.
c)The capillaries form a looped arrangement at following locations:
i) Vascular papillae of skin.
ii)Tongue.

25. B. SIMPLE ARTERIOVENOUS ANASTOMOSIS:
• It is formed by union of
smaller arteries and
veins.
• The connecting vessels
are straight or coiled,
have a thick muscular
coat and average
diameter of 20 µm.

26. • These vessels are richly
supplied with
unmylenated
sympathetic nerve
fibres.
• Under the influence of
sympathetic activity
vessels remain closed
and blood passes
through capillary bed in
an ordinary way and
when they are open the
blood passes directly
from arteries into veins.

27. Sites:
i) Skin of Nose.
ii) Skin of Lips.
iii) Skin of External Ear.
iv) Mucous membrane of Nose.
v) Mucous membrane of alimentary canal.
vi) Erectile tissue of sexual organs.
vii) Thyroid gland.
viii) Coccygeal body.
ix) Sympathetic ganglia.

29. C. COMPLEX ARTERIO-VENOUS ANASTOMOSIS OR
GLOMUS :Site: They are seen in skin of hands and feet especially the
digital pads and nail beds. They are situated in dermis of
skin.
Description:
An arteriole, just before it gives rise to its capillary
network, also gives rise to 2-4 short tortuous vessels.
These tortuous vessels are anastomotic channels of
glomus.
They show following peculiarities.
1) The endothelium forms a cushion like elevation near
their origin from the arteriole. The smooth muscle cells
are also developed. This mechanism serves as a valve.
2) There is no elastic tissue.

31. 3) Collagenous & reticulin fibres and short
contractile epitheloid pale staining cells are common.
4) They open directly into the large venous segments
(funnel shaped vein) which lead in to a vein
(collecting vein).
Functions:
They are concerned with local regulation of
peripheral circulation and thereby control the
temperature and tissue nutrition.
Clinical Significance:
Certain vascular ailments of limbs are due to
abnormality in structure or functioning of glomus
mechanism.

32. Overall Functions of Arteriovenous Anastomoses:
1. They regulate blood pressure.
2. They regulate the secretions of epitheloid cells.
3. They control pressor reception.
4. They control local body temperature by relaxation.
(either the temperature is raised or lowered).

33. 5. They control local nutrition.
6. They help to increase the pressure in portal vein
when absorption is not occurring in intestine. In this
situation blood directly starts flowing from arterioles
to venules in the villi and by-pass the capillary
network.
7. They help in absorption from intestine. During
absorption the direct arteriovenous connection is
closed and blood passes through capillary network
present at the tips of the villi and hence promotes
absorption of nutrient material.

34. SIGNIFICANCE OF ANASTOMOSES:
1. They help in maintenance of equal pressure in
the area supplied by them.
2. They provide alternate channels of supply to a
particular area.
3. Clinically, the anastomosis provide, by their
enlargement, the basis of collateral circulation, when
a vessel is occluded by ligation or disease.

35. MECHANISM OF DILATATION OF ANASTOMOTIC
CHANNELS OR COLLATERAL CHANNELS:
The mechanism of dilatation of anastomotic channel
is ill-understood. However, following factors may play
some role:
1. Decrease in peripheral resistance.
2. Hypoxia.
3. Nervous factors.
4. Accumulated metabolites.
5. Younger age.

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