Heat regulation

Bones

Vascular system

RETICULATED GIRAFFE Giraffa reticulata

MALE

FEMALE

Life span

Weight 2,600 lbs

25 years

1,750 lbs

Height 17 ft

14 ft

An agile, thick tongue that can be up to 20 inches long, grasps leaves while tough skin in the mouth protects against thorns. The tip of the tongue is black, possibly for sun protection.

ANGLING FOR ADVANTAGE A joint at the base of the skull allows the head to lift into a line nearly vertical with the neck.

Scientists theorize that clusters of blood vessels and sweat glands under each brown patch release heat.

Arteries

Scapula

Vertebrae

Esophagus

Heart

Humerus

Metacarpal

THE POWER BASE As giraffes grow, their leg bones thicken, narrowing the marrow cavity and support ing increasing weight. Bones are especially long and straight in the lower legs.

ARTERIES AND GRAVITY Arteries above the heart are muscular and elastic to pump blood against gravity to the brain. Lower arteries are narrower with thick walls to bear higher pressures and to prevent blood from pooling.

Neck artery

Leg artery

MULTITASKING HEART The left ventricle has thick muscular walls to pump blood up to the head and then around the body. The thinner right ventricle pumps blood a short distance to the lungs.

Right ventricle wall

Left ventricle wall

ADJUSTING FOR PRESSURE A network of elastic vessels expands when the head is lowered, to prevent blood from flooding the brain, and constricts when the head is raised, to prevent quick depletion

Brain

Elastic vessels

Open valve

Closed valve

When the head is lowered, valves in the veins close to prevent backflow of blood.

WHY THE LONG NECK?

The reason for the giraffe’s six-foot neck remains a mystery. It may have evolved to reach high branches, above competitors. Other theories suggest it improved vigilance or that longer necks provided an advantage to males fighting to win a mate.

Feeding

Surveying

Fighting