According to the University of California, parallel veins are the veins in leaves of a plant that run in the same direction as one another. The other type of venation in plant leaves is netted. The type of venation in a plant leaf influences a plant's classification.
Plants with parallel veins include corn, grasses and lilies. These plants generally belong to the monocot family. Parallel venation describes leaves in which the major veins all run lengthwise along the leaf. Those leaves with a netted vein structure belong to the dicots. With netted veins, the main veins branch into smaller and smaller veins. Sometimes, a leaf's venation is not a reliable classification factor for the plant because the veins on the leaves of some monocots, such as the aroids, have a more netted appearance.Learn More
Veins have valves to prevent the backflow of blood, according to Professor Tamarkin at Springfield Technical Community College. Veins carry blood from the body back to the heart, so they need these one-way valves to prevent blood from flowing backward.Full Answer >
Common causes for distended neck veins include pulmonary embolism, constrictive pericarditis and a failing right side of the heart, according to Right Diagnosis. Distended neck veins can also be caused by pericardial effusion, restrictive cardiomyopathy or ventricular tachycardia.Full Answer >
Veins are responsible for transporting blood from parts of the body back to the heart. There are four types of veins; pulmonary, systemic, superficial and deep veins. The inner structure of veins consists of valves that keep the movement of blood from backing up.Full Answer >
Blood moves through veins when it is pushed by muscle contractions. Unlike arteries, which carry blood away from the heart in response to the rhythmic contractions of the left ventricle, veins are a low-pressure system that pushes blood toward the heart by means of a series of smooth muscle contractions known as peristalsis.Full Answer >