Heart
Sharks have a two-chambered heart, with an atrium (also called the auricle) and a ventricle. The heart is an S-shaped tube that is located in the head region of the shark.

Blood is pumped by the heart through the afferent branchial arteries (ventral aorta) to capillaries in the gills (where the blood is oxygenated).


Liver

• The liver of sharks occupies most of the body cavity. This large, soft and oily organ can comprise up to 25% of the total body weight.

Pancreas

• The pancreas is a digestive gland with two pink lobes. Secretions pass from this organ to the duodenum from the ventral lobe through a small duct.

Stomach

• The stomach can be seen within the body cavity. Often found within the stomach are the contents of the sharks last meal.

Kidney

• Kidney role is to maintain the homeostatic balance of bodily fluids by filtering and secreting metabolites (such as urea) and minerals from the blood and excreting them, along with water, as urine.

Dorsal Aorta

• Dorsal Aorta carries oxygenated blood from the gills to the systemic circulation.

Oesophagus

• The shark’s oesophagus is short and wide allowing smaller prey to be swallowed whole or large chunks of prey to be gulped down as sharks do not chew their food.

So how does the Shark internal body works?

Muscles

• Sharks have 3 main muscle classes:
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  Cardiac muscle in the heart which works continuously
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  Visceral muscles / smooth muscles in various internal parts such as the guts, arteries, excretory and reproductive organs. Contraction of these muscles allows passage of contents through these parts.
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  Skeletal muscles that move the skeleton are comprised of 2 types:

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    Red muscles, It has a good blood supply and allows the shark to swim slowly for long periods without tiring
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    White muscles, works by using the energy from the breakdown of sugars; it has a poor blood supply and is used only for short fast bursts of swimming when chasing prey or avoiding danger.

Blood

• Composed of 55% plasma which contains: water (90%), dissolved proteins, glucose, minerals, hormones, gases, platelets and blood cells. Red blood cells contain hemoglobin. This binds to oxygen and gets transported around the shark’s body.

Immunity

• Sharks possess 2 types of immunity.
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  Natural or Innate Immunity, provides the first line of defense against invading pathogens
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  Specific or Adaptive Immunity is when immunological memory is generated following an initial
  exposure to an infectious pathogen.

Temperature

• The body temperature of the shark is at about the same temperature as its surrounding habitat, making most species “cold-blooded”

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