Human Body Systems: Skeletal, Endocrine, Digestive, Respiratory
Skeletal System
The skeletal system provides support, protection, mineral storage, hematopoiesis (blood cell formation), and enables movement.
Types of Bones
- Long bones
- Irregular bones (e.g., vertebrae)
- Short bones (e.g., carpals, tarsals, ossicles)
- Flat bones (e.g., cranial bones, sternum, hip bones)
Bone Structure
- Diaphysis: The shaft of a long bone, composed of hard compact bone.
- Epiphysis: The ends of a long bone, composed of spongy bone.
Internal Structure
- Medullary cavity: A hollow space within the diaphysis, containing yellow bone marrow.
- Endosteum: A membrane lining the medullary cavity.
External Structure
- Articular cartilage: Cartilage covering the epiphysis, providing cushioning.
- Periosteum: A fibrous covering of long bones, except where articular cartilage is present.
Bone Growth and Formation
- Osteoblasts: Bone-forming cells.
- Osteoclasts: Bone-resorbing cells.
- Ossification: The process of replacing other tissues with bone. It begins deep in the dermis with the development of osteoblasts.
- Osteogenesis: Bone formation.
Bone Cells
- Osteoblast: Creates bone.
- Osteocyte: Creates space between the bones (lacuna).
- Osteoclast: Gives shape to bones.
Skull Bones
- Parietal: Forms the upper part of the braincase.
- Occipital: Forms the back of the head.
- Temporal: Contains structures for hearing and balance.
- Zygomatic: Forms the cheekbone and part of the eye orbit.
- Mandible: The lower jaw, involved in chewing and speaking.
- Maxilla: The upper jaw, involved in chewing.
- Lacrimal: Forms part of the eye socket.
- Nasal: Forms the bridge of the nose.
- Ethmoid: Separates the nasal cavity from the brain.
- Sphenoid: Houses the pituitary gland.
- Frontal: Protects the brain and forms the upper part of the eye orbit.
Bones of the Body
- Clavicle: Supports the scapula and sternum.
- Scapula: Enables shoulder movement.
- Humerus: Provides movement and rigidity to the arm.
- Ulna and Radius: Provide movement and rigidity to the forearm.
- Carpus: Bones of the hand.
- Metatarsus: Bones of the fingers.
- Fibula: Provides support and stability (also known as the calf bone).
- Tibia: Supports body weight.
- Femur: Enables movement of the leg.
- Hip bone: Supports the weight of the upper body.
- Vertebral column: Supports the body.
- Ribs: Protect internal organs.
- Sternum: Protects internal organs and articulates with the ribs.
Endocrine System
The endocrine system is a set of glands that produce hormones, which are chemical messengers that regulate various bodily functions.
Endocrine Glands and Their Hormones
- Hypothalamus: Stimulates the pituitary gland.
- Pituitary Gland
- Antidiuretic hormone (ADH): Regulates water retention in the kidneys and controls blood pressure.
- Corticotropin: Controls hormone production in the adrenal cortex.
- Growth hormone (GH): Stimulates the production of proteins.
- Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH): Regulate reproductive function and sexual characteristics.
- Oxytocin: Stimulates uterine contractions during childbirth.
- Thyroid-stimulating hormone (TSH): Stimulates the production of thyroid hormones.
- Thyroid Gland
- Thyroid hormone: Affects growth, maturity, and metabolism.
- Thyroxine: Regulates metabolism.
- Adrenal Glands
- Aldosterone: Regulates salt and water balance in cells.
- Corticosteroids: Have anti-inflammatory effects and maintain blood sugar levels, blood pressure, and muscle strength.
- Renin and Angiotensin: Regulate blood pressure.
- Erythropoietin: Stimulates red blood cell production.
- Testicles: Produce testosterone, which is responsible for male sex characteristics.
- Parathyroid Glands: Regulate calcium and phosphorus absorption.
- Pancreas
- Glucagon: Increases blood sugar levels.
- Insulin: Decreases blood sugar levels.
- Ovaries: Produce estrogen (responsible for female sexual characteristics) and progesterone (involved in fertilization and milk production).
Digestive System
The digestive system is a series of organs and glands that work together to convert food into essential nutrients, which are then absorbed by the body.
Organs and Their Functions
- Mouth: Begins the process of food degradation.
- Pharynx: Connects the mouth to the esophagus.
- Esophagus: Moves the bolus (food mass) into the stomach.
- Stomach: Mixes and grinds food.
- Small Intestine: Responsible for nutrient absorption.
- Duodenum: Breaks down food.
- Jejunum: Absorbs nutrients into the bloodstream.
- Ileum: Absorbs vitamin B12 and bile salts.
- Colon: Absorbs remaining nutrients and liquids.
- Liver: Produces bile, which aids in fat digestion.
- Pancreas: Produces insulin, which regulates blood sugar.
- Gallbladder: Stores bile produced by the liver.
Respiratory System
Organs and Their Functions
- Nasal cavity: Contains mucous membranes and tiny hairs (cilia) that filter and warm inhaled air.
- Pharynx: A passageway for both food and air.
- Epiglottis: A flap of tissue that prevents food from entering the airway during swallowing.
- Larynx: Connects the pharynx to the trachea and contains the vocal cords.
- Trachea: The main airway to the lungs.
- Pleura: Membranes that cover the outside of the lungs and protect them from friction against the ribs.
- Lungs: The primary organs of respiration, where gas exchange (oxygen and carbon dioxide) takes place in the alveoli.