- to propel blood
- to maintain blood pressure
Function of the blood
- to transport oxygen and carbon dioxide
- to deliver nutrients and hormones
- to remove waste products
- to assist in defense against disease
Function of blood vessels
- to distribute blood throughout the body
Blood vessels consist of:
- arteries, which carry blood from heart to capillaries
- capillaries, the smallest of the vessels and sites of exchange between blood and interstitial fluids
- veins, which return blood from capillaries to the heart
Arteries are large diameter vessels that carry oxygenated blood away from the heart. Arteries gradually decrease in size to become arterioles, the smallest vessels of the arterial system. From here, blood enters the capillaries to serve local tissues.
Blood flowing toward the heart begins in the tissues and flows through venules, which are the smallest vessels of the venous system. The pathway increases to larger and larger vessels called veins, which carry non-oxygenated blood back toward the heart.
Arteries and veins often lay side by side in a narrow band of connective tissue.
The walls of arteries and veins contain three layers:
- tunica interna (tunica intima) is the innermost layer, which includes the endothelial lining and an underlying layer of connective tissue dominated by elastic fibers.
- tunica media is the middle layer of smooth muscle tissue in a framework of collagen and elastic fibers. When the smooth muscles contract, the vessels decrease in diameter. When they relax, the diameter increases. The tunica media of an artery contains more smooth muscle and elastic fibers than a vein does.
- tunica externa (tunica adventitia) forms a sheath of connective tissue around the vessel. Its collagen fibers may intertwine with those of adjacent tissues which stabilize and anchor the blood vessel.
- small and large intestines
Accessory organs include:
- salivary glands
- Endocrine glands: adrenals, gonads, hypothalamus, pancreas, parathyroid, pineal, pituitary, thymus, thyroid
- Other organs that secrete hormones: heart, kidneys, digestive tract, pancreatic islets, gonads
- protection of soft tissues;
- mineral storage;
- blood formation.
There are 206 bones in the human body.
The skeleton is divided into two sections:
- axial skeleton: consists of the skull, vertebrae, sacrum, ribs, and sternum. The axial skeletal system protects the brain, spinal cord, sensory organs, and soft tissue of chest cavity and supports the body weight over the legs.
- appendicular skeleton: consists of the limbs and supporting bones. The appendicular skeletal system provides internal support and positioning of arms and legs. It also supports and moves the axial skeleton.
Types of Bone Tissue:
- Compact bone is comprised of osteon or haversian system, a term describing the very precise arrangements of osteocytes, matrix, and blood vessels of bone. Halversian was named for Clopton Havers, a 17th century English anatomist who wrote a book on bone structure. The arrangement involves cylinders of bone matrix with osteocytes in concentric rings around central haversian canals (blood vessels). The osteocytes (bone cells) are in contact with the blood vessels and with each other through microscopic channels (canaliculi) in the matrix. The matrix of bone contains calcium salts (calcium carbonate – CaCO3, and calcium phosphate – Ca3(PO4)2, and collagen.
- Spongy bone is named for its appearance. Osteocytes, blood vessels, and matrix are present, but not arranged in haversian systems. The cavities often contain red bone marrow, which produces RBCs, platelets, and five types of WBCs.
Classification of Bones:
- Long bones are the bones of the arms, legs, hands, and feet. The shaft is called the diaphysis (hollow, but made of compact bone to form a canal within the shaft known as the marrow canal). The ends are called epiphyses (made of spongy bone covered with a thin layer of compact bone, as are the short, flat, and irregular bones). The marrow canal, or medullary cavity, contains yellow bone marrow, which is mostly adipose tissue which gradually replaces the red bone marrow during aging.
- Short bones are the bones of the wrists and ankles.
- Flat bones are the bones of the ribs, shoulder blades, hips, and cranium.
- Irregular bones are those of the vertebrae and face.
- Largest are the right lobe and the left lobeSmaller are the caudate lobe and quadrate lobe
Falciform ligament is the tough connective tissue fold that divides the right and left lobes.
The liver lobule is the basic functional unit of the liver. There are about 100,000 of them in the liver.
Hepatocytes are liver cells. They are arranged in a series of irregular plates like the spokes of a wheel. Liver cells produce about one liter of bile every day. Bile is secreted and released into a network of channels called bile canaliculi, which carry the bile away from the central vein and toward larger bile ducts leading to the common hepatic duct. This eventually ends up in the gallbladder for storage. The gallbladder lies under the right lobe of the liver.
Sinusoids are specialized highly permeable capillaries that form passageways between the plates, emptying into the central vein. The sinusoid lining is made up of the typical endothelial cells as well as a large number of phagocytic cells called Kupffer cells, which engulf pathogens, cellular debris, and damaged blood cells. Blood enters the sinusoids from branches of the hepatic portal vein and hepatic artery and leaves through the central vein of the lobule.
Liver diseases lead to degenerative changes in the tissue that cause constriction of blood flow, causing the tissue to die. Liver disease is often the result of such conditions as fibrosis, cirrhosis, or hepatitis. One or more of these three conditions can exist at the same time.
Fibrosis is the initial stage of scar tissue formation.
Cirrhosis is the irreversible scarring of the liver.
Hepatitis simply means an inflammation, but the effects are far from simple.
The lymphatic system consists of
- lymph – a fluid that resembles plasma but with much lower concentrations of proteins
- lymphatic vessels – called lymphatics, a network that carries lymph from peripheral tissues to the venous system
- lymphoid organs – including lymph nodes, tonsils, thymus gland, and spleen. They are connected to lymphatic vessels and contain large numbers of lymphocytes.
- lymphatic tissues – connective tissues dominated by lymphocytes
The lymphatic system is widely scattered throughout the body and has three main functions.
- Its vessels return cleansed tissue fluid to the blood.
- Its capillaries (lacteals) play an important role in the intestinal absorption of fats and fat-soluble vitamins.
- Its tissues help the body defend itself against disease.
The muscular system consists of all skeletal muscles that can be controlled voluntarily.
Skeletal muscles (700):
- provide skeletal movement;
- control entrances and exits of digestive tract;
- produce heat;
- support skeletal position;
- protect soft tissues.
Almost all skeletal muscles either originate or insert on the skeleton producing various forms of movement: flexion, extension, adduction, abduction, protraction, retraction, elevation, depression, rotation, circumduction, pronation, supination, inversion, or eversion.
Axial muscles support and position axial skeleton.
Appendicular muscles support, move, and brace limbs.
Cardiac muscle is found only in the heart and consists of specialized cells that establish a regular rate of contraction independent from nervous system influence.
Smooth muscle acts either independently or in response to neural activity. Smooth muscle is found within almost every organ forming sheets, bundles, or sheaths around other tissues regulating movement of that particular organ:
- walls of blood vessels
- hollow organs such as urinary bladder
- layers around respiratory, circulatory, digestive, and reproductive tracts
The primary reproductive organs are called gonads.
Female gonads are called ovaries.
Male gonads are called the testes (or testicles).
Gonads have two functions:
- secrete hormones
- produce gametes (eggs or sperm)
The Respiratory System consists of
- nasal cavities and sinuses
- larynx, trachea
- bronchial tree
- pleural membranes
Functions of the Respiratory system
- Breathing – Inhalation and exhalation moves air into and out of the lungs. One of each forms the respiratory cycle.
- Exchange of the respiratory gases (oxygen and carbon dioxide) occurs in the alveoli and pulmonary capillaries.
- Blood transport of oxygen and carbon dioxide between the lungs and the body cells.
There are four major tissue types in the human body.
The urinary system consists of
- urinary bladder
The main function of the urinary system is to eliminate excess water, salts, and waste products.
Main structures and function
- Kidneys – form and concentrate urine – regulate chemical composition of the blood
- Ureters – conduct urine from the kidneys to the urinary bladder
- Urinary bladder – stores urine for eventual elimination
- Urethra – conducts urine to exterior
Organs of excretion
- Kidneys eliminate water, electrolytes, nitrogenous waste, and drugs.
- Skin sweats out water, electrolytes, and nitrogenous waste.
- Lungs eliminate carbon dioxide and water through respiration.
- Intestines eliminate digestive waste and bile pigments.