this content will be beneficial for b.sc nursing students

1. BLOOD VESSELS

2. BLOOD VESSELS
There are three main types of blood vessels
•Arteries
•Veins
•Capillaries

3. Structure:
In general all blood vessel walls, except the capillaries,
have three coats: tunica intima, tunica media and
tunica adventitia.
1) Tunica intima: It is the innermost coat and consists
of a single continuous layer of endothelial cells.
2) Tunica media: It is middle coat and consist of
smooth muscle cells and elastic fibres. It provide
mechanical strength to blood vessels.
3) Tunica adventitia: It is the outermost coat and is
made up of collagen and fibroblasts.

4. ARTERIES
ARTERIOLES
CAPILLARIES
VENULES
VEINS

6. Difference between Arteries & Veins:
Arteries
1) They transport blood away from
the heart.
2) Their walls are thicker and stronger
because of presence of more
smooth muscle cells & elastic
fibres.
3) They are characterized by thick
tunica media and thin tunica
adventitia.
4) They can withstand high pressure
and blood flows at much higher
pressure within them.
5) They retain the circular shape of
their lumen when empty.
Veins
1) They return blood at low
pressure to heart.
2) They are less elastic and
relatively thin walls.
3) Tunica adventitia is
thicker whereas tunica
media is thin.
4) These vessels are adapted
to withstand low pressure
only.
5) They collapse when
empty.

8. LYMPHATIC SYSTEM:
•The lymphatic system includes lymphatic vessels, lymph
and lymphatic organs (lymph node, thymus gland and
spleen)
1): Lymphatic vessels is a system of network that carry
lymph from the peripheral tissues to the venous system.
Lymphatics begin as narrow passageways called
lymphatic capillaries in areas of loose connective
tissues. Interstitial fluid enters these capillaries called as
lymph and moves into larger lymphatic vessels.
Lymphatic vessels empty into two large collecting ducts
(thoracic and right lymphatic duct. Both these larger
ducts empty into the venous system near the junction
between internal jugular vein and subclavian vein.

10. 2) Lymph: the tissue fluid absorbed in lymphatic
vessels is called lymph. It resembles plasma but
contains less concentration of proteins.
3) Lymphatic organs:
Lymph nodes: lymph nodes are intermediate
stations in the course of vessels at sites where a
number of smaller vessels joint to form a larger
vessel. Lymph nodes are little bean-shaped organs of
different sizes.
Sites: Neck, armpits, groin, mediastinum and the
two lungs, mesentry and pelvis.

12. Structure:
a) They have an outer capsule of fibrous tissues which
dip down into the substance of the node forming
partitions (or trabeculae).
b) The medulla or the inner main substance of the
node consists of reticular connective tissue and
lymphatic tissue which contains many lymphocytes
and macrophages.
c) Each node has a concave surface called the hilum
where an artery enters and a vein and an efferent
lymph vessel leave.
d) Four or five afferent lymph vessels may enter a
lymph node while only one large efferent vessel
carries lymph away form the node.

13. Function:
a) As a filter, lymph nodes engulf debris or pathogens
in the lymph as it proceeds towards the venous
system. The swollen glands (lymphadenopathy)
usually indicate inflammation or infection of
peripheral structures.
b) Defence function: lymph nodes form large number
of lymphocytes which after contact with an antigen
bring about immunity.
c) Serve as way station for migrating cancer cells.
Thus, their analysis can provide information on the
spread of cancer cells.

14. Thymus Gland:
a) The thymus lies behind the sternum,
in the anterior mediastinum. It
reaches its greatest size in the first
year after birth or during puberty.
Thereafter, it gradually decreases in
size and becomes increasingly fibrous
a process called involution.
b) The capsule that covers the thymus
divides it into two thymic lobes. Each
lobe consists of outer cortex and a
central medulla.
c) Lymphocytes in the cortex undergo
mitosis that finally develop into T-
lymphocytes and bring cell- mediated
immunity.

15. Spleen :
a) The spleen is located in the left upper part of the
abdominal cavity, below the diaphragm and behind
the stomach.
b) It has deep red colour due to blood it contains. It
has a soft consistency and the shape changes as
the stomach fills and empties.
c) Its structure is same as that of a lymph node i.e.
capsule, trabeculae and medulla.

16. Function:
a) Spleen can be considered a large lymph node in the
blood circulation and performs the same functions
for the blood that the lymph node perform for the
lymph.
b) As a reservoir of blood, i.e. useful to mobilise extra
blood into circulation.
c) Phagocytosis of abnormal blood components
d) Initiate immune response by B and T-lymphocytes.