Shape of Spleen
The spleen is an ovoid, usually purplish, pulpy, soft, vascular (sinusoidal) mass about the size and shape of one's fist. The spleen is 1 inch thick, 3 inches wide, 5 inches long, and weighs 7 ounces.

Location of Spleen
Spleen is located in left upper part of abdomen or hypochondrium. It lies just beneath the left half of the diaphragm close to the 9th, 10th, and 11th ribs. The long axis lies along the shaft of the 10th rib, and extends forward only as far as the midaxillary line and cannot be palpated on clinical examination. When it is palpable under left hypochondrium, it is generally 2-3 times enlarged in size.
Coverings of Spleen
The spleen is covered by fibroelastic capsule and is surrounded by peritoneum except at the splenic hilum, (the splenic branches of the splenic artery and vein enter and leave at hilum).

Presenting parts of Spleen

  • Diaphragmatic surface
  • Visceral surface
  • Superior border
  • Inferior border
  • Anterior or lateral end
  • Posterior or medial end

Ligaments of Spleen

Gastrosplenic ligament
It is the fold of peritoneum that connects spleen with greater curvature of stomach.

Splenorenal/lienorenal ligament 
It is the fold of peritoneum that connects spleen to the left kidney.

These two ligaments are attached to the hilum of spleen. Splenorenal ligament carries splenic vessels and sometimes tail of pancreas.

Phrenicocolic ligament 
It is attached to the left colic flexure (colon) and diaphragm. This ligament supports the spleen from below.

Important relations of Spleen

Anteriorly, the stomach, and tail of pancreas
Posteriorly, the left part of the diaphragm,which separates it from the pleura, lung, and ribs 9th, 10th and 11th.
Inferiorly, the left colic flexure.
Medially, the left kidney.

Blood Supply of Spleen
The spleen normally contains a large quantity of blood that is expelled periodically into the circulation by the action of the smooth muscle in its capsule and trabeculae. The large size of the splenic artery (or vein) indicates the volume of blood that passes through the spleen's capillaries and sinuses. The thin fibrous capsule of the spleen is composed of dense, irregular, fibroelastic connective tissue. The fibrous capsule is thickened at the splenic hilum. Internally the trabeculae, arising from the deep aspect of the capsule, carry blood vessels to and from the parenchyma or splenic pulp, the substance of the spleen.

Arteries of Spleen
The large splenic artery is the largest branch of the celiac artery. It has a tortuous course as it runs along the upper border of the pancreas. The splenic artery then divides into about six branches, which enter the spleen at the hilum.

Veins of Spleen
The splenic vein leaves the hilum and runs behind the tail and the body of the pancreas. Behind the neck of the pancreas, the splenic vein joins the superior mesenteric vein to form the portal vein.

Lymph Drainage of Spleen
The lymph vessels emerge from the hilum and pass through a few lymph nodes along the course of the splenic artery and then drain into the celiac nodes.

Nerve Supply of Spleen
The nerves accompany the splenic artery and are derived from the celiac plexus.

Also Read:
Histological features of spleen

Following resources are used while preparing this post (readers are strongly recommended to go through them for more details):
Gray's Anatomy
K. L. Moore's Clinically Oriented Anatomy
R. Snell's Clinical Anatomy