Page 124 - Biology Form Two

Biology for Secondary Schools

Capillary Tissue fluid
Tissue cells
Arteriole Direction of
blood flow

Venule
FOR ONLINE READING ONLY

Tissue fluid
enters capillary

Tissue fluid released from capillary
Lymphatic vessel

Figure 5.16: Formation of tissue fluid in a capillary bed

At the venous end of the capillary, Importance of blood circulation
blood pressure is low; water potential Blood circulation enables the
is also low. The pressure of the tissue transportation of cell requirements such

fluid is high. This forces the tissue fluid as oxygen and nutrients to all tissues. It
back into the capillaries. Diffusion also ensures that waste products from
also helps in the re-entry of the tissue the cells are removed in order to prevent
accumulation. The accumulation of
fluid into the capillary. However, some waste products is harmful to the body.

tissue fluid remains within the cells.
It later enters the lymphatic system to Blood circulation is also important for
form lymph fluid. the regulation of body temperature. Heat
is transported to all parts of the body
The capillaries join to form venules. through this system. Moreover, blood

The venules join to form veins, which circulation transports hormones from the
transport blood back to the heart. Veins organs that produce them to the organs
in the lower part of the body unite to where they are needed. For example,
insulin from the pancreas is necessary
form the inferior vena cava, while for regulating of blood sugar levels.

those in the upper part of the body
unite to form the superior vena cava. Blood pressure
These two large veins join to form the When ventricles contract and blood is
vena cava which transports blood to pumped into arteries, it causes systolic
pressure. On the other hand, when
the right auricle of the heart.
auricles contract and pump blood into
ventricles, it causes diastolic pressure.

118 Student’s Book - Form Two

05/10/2024 15:36:41
BIOLOGY FORM 2 NEW.indd 118 05/10/2024 15:36:41
BIOLOGY FORM 2 NEW.indd 118