Human Biology Basics: Cells, Tissues, and Organ Systems

Lymph keeps the body cells moist. It transfers oxygen, hormones, and nutrients to different parts of the body and removes metabolic waste from the cells. It transports antibodies and lymphocytes to the blood. Lymph also maintains the composition of the tissue fluid and volume of the blood. Absorption of fat from the small intestine occurs through lymphatic vessels.

The air pressure in our lungs varies during breathing. When air pressure falls, the alveolar spaces expand, and air enters the lungs (inspiration). When the pressure within the alveoli exceeds atmospheric pressure, air is expelled from the lungs (expiration). The flow rate of air is proportional to the pressure difference.

The breathing mechanism involves two processes:

• Inspiration
• Expiration

During inspiration, the muscles attached to the ribs contract, pulling the ribs outward and expanding the chest cavity.

The diaphragm contracts and moves downward, further expanding the chest cavity. This also results in the contraction of the abdominal muscles.

The expansion of the chest cavity creates a partial vacuum, which draws air into the lungs and fills the expanded alveoli.

• The process of taking in atmospheric air is known as inspiration. It is an active process.
• Inspiration occurs when the volume of the thoracic cavity increases, and the air pressure decreases.
• Contraction of external intercostal muscles increases the volume of the thoracic cavity.
• Contraction of the diaphragm further increases the size of the thoracic cavity. Simultaneously, the lungs expand.
• As the lungs expand, the air pressure inside the lungs decreases.
• The pressure equalizes, and atmospheric air rushes into the lungs.

The heart’s primary function is to pump blood throughout the body. It supplies oxygen and nutrients to the tissues and removes carbon dioxide and waste from the blood. It also helps maintain adequate blood pressure throughout the body. The heart plays an important role in maintaining body temperature by pumping blood.

The pancreas is a mixed or heterocrine gland. Oogenesis is the process of formation of female gametes.

Skin is made up of three layers: the epidermis, dermis, and the hypodermis.

A neuron has three main parts: dendrites, an axon, and a cell body or soma.

Your blood group is identified by antibodies and antigens in the blood. O negative donors are often called “universal donors”. AB+ is the universal acceptor.

Bones of the hand: The carpus (proximal and distal rows), metacarpal bones, phalanges, and various sesamoid bones form the skeletal hand. The hand has five metacarpals, fourteen phalanges, and four consistently present sesamoid bones.

Hematopoiesis is blood cell production.

The clotting factors are Factor I (fibrinogen), Factor II (prothrombin), Factor III (tissue thromboplastin or tissue factor), Factor IV (ionized calcium), Factor V (labile factor or proaccelerin), Factor VII (stable factor or proconvertin), and Factor VIII (antihemophilic factor).

Mitochondria are called the powerhouse of the cell. Flexion refers to a movement that decreases the angle between two body parts.

The study of the structure of a plant or animal is called anatomy.

A surgical suture, also known as a stitch or stitches, is a medical device used to hold body tissues together and approximate wound edges after an injury or surgery.

The five parts of your axial skeleton include the bones in your skull, ossicles (small bones) of your middle ear, hyoid bone of your neck, vertebrae (bones of your spine), and thoracic cage (ribcage).

The spleen is a highly vascular lymphoid organ present in the body.

Lymph nodes are small glandular structures located along lymph vessels.

The process by which the formed elements of blood develop is called hemopoiesis or hematopoiesis.

The salivary glands in many vertebrates, including mammals, are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Function: Human salivary glands produce between 0.5 to 1.5 L of saliva daily, facilitating mastication, swallowing, and speech, lubricating the oral mucosa, and providing an aqueous medium for taste perception.

Functions of the brain: Thoughts and decisions, memories and emotions, movements (motor function), balance and coordination, perception of various sensations including pain, automatic behavior such as breathing, heart rate, sleep and temperature control, regulation of organ function, speech and language functions.

Functions of the Spleen: The spleen plays an important role in hematopoietic function in the embryo. The spleen is also called the graveyard of RBCs because it participates in the destruction of RBCs and other old blood cells.

Blood is a special type of fluid connective tissue consisting of a clear, straw-colored, watery, non-living fluid matrix (plasma) and living blood cells (formed elements). Composition of blood: Blood plasma (plasma proteins, inorganic salts, nutrients from digested foods, waste materials, hormones, gases), formed elements (RBCs, WBCs, platelets).

Blood Plasma is the straw-colored fluid constituting nearly 55 percent of the blood. 90-92 percent of plasma is water, and proteins contribute 6-8 percent of it. Plasma proteins: Albumins, Globulins, Fibrinogen.

Functions of blood: Blood performs several functions, all concerned with transporting substances, regulating blood levels of particular substances, or protecting the body. Transport: Transporting oxygen and carbon dioxide from the lungs to other parts of the body, transporting nutrients and waste materials from metabolic sites to eliminating sites, transporting hormones from the endocrine organs to their target organs. Regulation: Regulates fluid volume by releasing inorganic salts (Na+, Ca2+, K+, HCO3- etc.) and maintaining normal pH in body tissue, maintains body temperature by absorbing and distributing heat throughout the body and to the skin surface to encourage heat loss. Protection: Prevents blood loss; when a blood vessel is damaged, platelets and plasma proteins initiate clot formation, halting blood loss, prevents infection by producing antibodies and leukocytes, which help defend the body against foreign invaders such as bacteria and viruses.

The function of the renal/urinary system is to eliminate wastes from the body, regulate blood volume and pressure, control levels of electrolytes and metabolites, and regulate blood pH.

When we forcefully exhale, not all air is expelled. Some air remains in the anatomical dead space, which is 1200 mL in males and 1100 mL in females. This is known as residual volume.

Inspiratory capacity is the sum of tidal volume and inspiratory reserve volume (500 ml + 3100 ml = 3600 mL in males and 500 ml + 1900 mL = 2400 ml in females).

Functional residual capacity is the sum of residual volume and expiratory reserve volume (1200 mL + 1200 mL = 2400 mL in males and 1100 mL + 700 mL = 1800 mL in females).

Vital capacity is the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume (4800 mL in males and 3100 mL in females).

Total lung capacity is the sum of vital capacity and residual volume (4800 mL + 1200 ml = 6000 mL in males and 3100 mL + 1100 mL = 4200 ml in females).

The kidneys remove waste products and drugs from the body, balance the body’s fluids, release hormones that regulate blood pressure, produce an active form of vitamin D that promotes strong, healthy bones, and control the production of red blood cells.