Neurophysiology lecture notes, Lecture notes of Physiology

Download Neurophysiology lecture notes and more Lecture notes Physiology in PDF only on Docsity!

Spleen

• Lymphatic organ connected to blood vascular system
• Part of mononuclear phagocyte system.
• Wedge shaped

• it lies between the

fundus of the

stomach and the

diaphragm.

• the largest of the

ductless glands, and

is of an oblong,

flattened form, soft,

of very friable

consistence, highly

vascular, and of a

dark purplish color.

• 1" (2.5 cm) by

3“(7.5cm) by

5“(12.5cm)

• 150 grams (5.3 oz)

to 200 grams

(7.1 oz)

• lies between the

9th and 11th ribs

on the left hand

side.

Development

• Appears about the fifth week
• It arises in a series of hillocks, of the mesoderm in the dorsal mesogastrium above the tail of pancreas.
• With the change in position of the stomach the spleen is carried to the left, and comes to lie behind the stomach and in contact with the left kidney.
• The part of the dorsal mesogastrium between the spleen and the greater curvature of the stomach forms the gastrosplenic ligament.

• When the hillocks fail to unify
• 20% of persons.
• especially in the gastrolienal ligament and

greater omentum,

• vary in size from that of a pea to that of a plum.

Visceral surface

divided by a ridge

Gastric surface

• broad and concave
• is in contact with the posterior wall of the stomach; and below this with the tail of the pancreas.
• It presents near its medial border a long fissure, termed the hilum. This is pierced by several irregular apertures, for the entrance and exit of vessels and nerves.

Renal surface

• somewhat

flattened, is

considerably

narrower than the

gastric surface

• upper part of the

anterior surface of

the left kidney and

occasionally left

suprarenal gland.

• anterior border - is free, sharp, and thin, and is often notched, especially below
• posterior border- more rounded and blunter than the anterior, corresponds to the lower border of the eleventh rib and lies between the diaphragm and left kidney.
• The intermediate margin is the ridge which separates the renal and gastric surfaces.
• inferior border- rounded

Structure

External or serous coat ( tunica serosa )

• from the peritoneum
• thin, smooth, and intimately adherent to the fibroelastic coat. It invests the entire organ, except at the hilum and along the lines of reflection of the phrenicolienal and gastrolienal ligaments.

Fibroelastic coat ( tunica albuginea ) invests the organ, and at

the hilum is reflected inward upon the vessels in the form of sheaths. From these sheaths, as well as from the inner surface of the fibroelastic coat, numerous small fibrous bands, trabeculae are given off in all directions

• The fibroelastic coat, the sheaths of the vessels, and the trabeculæ, are composed of white and yellow elastic fibrous tissues
• spleen possesses a considerable amount of elasticity, which allows of the very great variations in size
• small amount of non- striped muscular fiber The spleen consists of a number of small spaces , formed by the trabeculæ which contain the splenic pulp.

• The spleen is made of red pulp and white

pulp, separated by the marginal zone; 76-

79% of a normal spleen is red pulp

red pulp

• Red blood–filled sinusoids and reticuloendothelial cell– lined cords of Billroth (connective tissue )
• Splenic cords - reticular fibers, reticular cells, and associated macrophages Sinusoids
• wide vessels that drain into trabecular veins.
• Gaps in the endothelium lining the sinusoids mechanically filter blood cells as they enter the spleen.