Introduction to Body Structure PDF

# INTRODUCTION TO BODY STRUCTURE ## TERMINOLOGY **Anatomical position:** all the anatomical descriptions are based on a position in which the man is standing, with his face & palms of hands directed forward & the feet are close to each other. **Anatomical planes & directions:** - **Median (sagit...

# INTRODUCTION TO BODY STRUCTURE ## TERMINOLOGY **Anatomical position:** all the anatomical descriptions are based on a position in which the man is standing, with his face & palms of hands directed forward & the feet are close to each other. **Anatomical planes & directions:** - **Median (sagittal) plane:** a vertical plane which divides the body at the midline into Rt & Lt equal halves. According to this plane & the planes parallel to it (paramedian or parasagittal planes) the body is divided into medial (near the midline) & lateral (away from midline). paramedian plane: each is a vertical plane, parallel to the median plane. - **Coronal plane:** a vertical plane which divides the body into anterior (in front of the plane) & posterior (behind the plane). - **Transverse (horizontal) plane:** which divides the body into superior (upper) & inferior (lower) parts. median plane dividing the body into RT and LT unequal parts accordingly the body is divided into medial and lateral. **Anatomical descriptions:** - **Superficial & deep:** near or away from the surface. - **External & internal:** outside or inside. - **Proximal & distal:** near or away from the trunk. **Terms of movements:** - **Flexion & extension:** moving 2 ventral surfaces towards or away from each other. - **Adduction & abduction:** movement towards or away from midline. - **Medial & lateral rotations:** moving the anterior side towards or away from the midline. **N.B.:** other terms of movements may be used in specific sites. ## SKIN & FASCIA ### SKIN **Layers;** it is formed of 2 layers: - **Epidermis:** outer tough layer. - **Dermis:** inner layer containing hair follicles, sweat glands, nerves, blood vessels & lymphatics. **Functions:** - Protection from external environment. - Sensations. - Regulation of body temperature. ### SUPERFICIAL FASCIA - Formed of loose connective tissue & fat. - It also contains nerves, blood vessels & lymphatics, transmitting it to skin. - It is absent in specific sites, e.g.: eye lids & scrotum. **Functions:** - Fat store. - Regulation of body temperature (fat prevent heat loss). Slim people feel cold more than fat people. - In females, it contains the mammary gland forming the breast. ### DEEP FASCIA - It is formed of dense connective tissue, to surround the deeper structures. - It is well developed in limbs, especially around the joints (to grasp the different structures passing) & in the palm of hand & sole of foot (for protection). - It is poorly developed in sites which need expansion, e.g.: face and thoracic and abdominal walls. ## BONES **Ossification of bones:** - **Membranous:** a connective tissue membrane will ossify into bone (e.g.: clavicle). - **Cartilaginous:** a membrane will be transformed into cartilage model which will ossify into bone (e.g.: all bones of the limbs except clavicle). **Growing long bone** - During development of long bones, it is formed of a membranous model, which mostly changes to a cartilage. - Before birth, the shaft is transformed into bone, it begins by a **primary center of ossification**. - After birth, each end is transformed into bone, it begins by a **secondary center of ossification**. - A disc of cartilage persists between the shaft and each end, it is called **epiphyseal plate of cartilage**. - The epiphyseal plate of cartilage add new cells to the shaft, this will increase bone length. - The newly formed part of the shaft (near epiphyseal plate of cartilage) is called **metaphysis**. - Later, the epiphyseal plate of cartilage ossifies, this will stop bone lengthening. - Usually the 2 epiphyseal plates of the same bone do not ossify at the same time. One (non growing) end ossifies around the age of 19 years in males (17 years in females). The other (growing) end will ossify around the age of 21 years in males (19 years in females) with variations. - The bone is covered by a **periosteum**. Periosteum add new cells-deep to it, causing an increase in bone width. - The bone shows a cavity. This cavity is lined with **endosteum** and contains **bone marrow**, which is responsible for formation of blood cells. - **Skull** is heavy, so **pneumatic bones** help to make it light. ## JOINTS **Definition:** meeting between 2 or more bones (or cartilages). **Types:** according to the tissue between the bones the joints is classified into: ### Fibrous: | Type | Features | Example | |---|---|---| | Syndesmosis | · Allows minimal movement · Does not ossify with age | Inf tibiofibular joint | | Suture | · Allows minimal movement · Ossify with age | Sagittal suture (in skull) | | Gomphosis | · Allows no movement · Does not ossify with age | Between teeth & gums | ### Cartilaginous: | Type | Features | Example | |---|---|---| | Primary cartilaginous | · Formed of hyaline cartilage · Allows no movement · Ossifies with age | Epiphyseal plate of cartilage | | Secondary cartilaginous | · Formed of fibrocartilage · Allows minimal movement · Usually does not ossify with age · Usually found in midline | Intervertebral disc | ### Synovial: | Type | Features | Example | |---|---|---| | Plane | Allows only gliding movement | Acromioclavicular | | Hinge | Uniaxial: allows only flexion & extension | Elbow | | Pivot | Uniaxial: allows only rotation | Horizontal Axis | | Modified hinge | Biaxial: allows flexion & extension + minimal rotation | Knee, condylar | | Ellipsoid | Biaxial: allows flexion & extension + adduction & abduction | Wrist | | Saddle | Multiaxial: allows flexion & extension + adduction & abduction + minimal rotation | Carpometacarpal of thumb | | Ball & socket | Multiaxial: allows flexion & extension + adduction & abduction + rotation | Shoulder, Hip | **Synovial Joint features:** - **Articular cartilages:** a layer of hyaline cartilage, covering the articular surfaces, for smooth movement. - **Capsule:** it is formed of fibrous tissue, which connect the articular surfaces - **Synovial membrane:** lines the capsule & covers intracapsular non articular structures. It makes the joint space closed & secretes synovial fluid, which is responsible for joint lubrication. - **Ligaments:** strong fibrous tissue, for joint stability. These ligaments may be capsular (thickened part of capsule), intracapsular or extracapsular. ## CARDIOVASCULAR SYSTEM ### HEART - It is a muscular organ which pumps blood to different parts of the body. - It has 4 chambers (Rt & Lt atria & Rt & Lt ventricles). - It is supplied by coronary arteries. Occlusion of a coronary artery may lead to angina. **Parts:** - **Rt atrium:** - It receives non oxygenated blood from different parts of the body (except the lungs) through SVC and IVC. - It transmits it through Rt A-V opening (guarded by tricuspid valve) to Rt ventricle. - **Rt ventricle:** - It receives non oxygenated blood from RT atrium. - It pumps it through pulmonary artery (guarded by pulmonary valve) to the lungs where it is oxygenated. - **Lt atrium:** - It receives oxygenated blood from lungs through pulmonary veins. - It transmits it through Lt A-V opening (guarded by mitral valve) to Lt ventricle. - **Lt ventricle:** - It receives oxygenated blood from Lt atrium. - It pumps it through aorta (guarded by aortic valve) to different parts of body. ### BLOOD VESSELS - **Arteries:** - It is blood vessels transmitting blood away from the heart. - It has an elastic wall, helping in its dilatation and constriction to regulate blood pressure. - All the arteries carry oxygenated blood except pulmonary arteries which carry non oxygenated blood. - The arteries divide into smaller arteries → arterioles → capillaries. - Usually, the arteries anastomose with each other. Those who don't anastomose are called end arteries. Occlusion of an end artery will lead to death of the part supplied by it. E.g.: in heart, lungs, kidneys, spleen, retina and CNS. ## CIRCULATIONS **Systemic circulation:** - It is between the heart and different tissues of the body. - Lt ventricle pumps oxygenated blood aorta → arteries → arterioles → capillaries (material exchange with cells) → venules → veins → SVC & IVC → Rt atrium. **Pulmonary circulation:** - It is between the heart and lungs. - Rt ventricle pumps non oxygenated blood → pulmonary arteries → arterioles → capillaries (gas exchange with lung alveoli) → venules → pulmonary veins → Lt atrium. **Portal circulation:** - Between the GIT & liver (interrupting GIT systemic circulation). - Capillaries of GIT (carrying absorbed nutrients) → venules → veins → portal vein → divides → liver sinusoids (adjustment of nutrient levels and detoxication). - So, the portal vein begins like a vein (union of smaller veins) and ends like an artery (giving divisions). ## INTRODUCTION TO BODY STRUCTURE **Capillaries:** - Small thin walled blood vessels. - It allows the movement of oxygen & nutrients from blood to intercellular tissues & CO2 & waste products in the opposite direction. **Sinusoids:** - Wider than capillaries. - It allows slow circulation. - E.g.: liver, spleen, suprarenals and bone marrow. **A-V shunts:** - Direct channels between arterioles and venules. - It allows rapid circulation (as in temperature regulation) and not concerned with material exchange. - E.g.: hands, feet and nose. **SYSTEMIC CIRCULATION** - This is the circulation of blood between the heart and the rest of the body. - It is a closed system, meaning that the blood always circulates within the body. - It is divided into two main parts: - Pulmonary circulation: Circulation of blood between the heart and the lungs. - Systemic circulation: Circulation of blood between the heart and the rest of the body. **Pulmonary circulation:** - It is the movement of blood from the heart to the lungs and back to the heart. - The blood is oxygenated in the lungs. - It is responsible for carrying oxygen to the body and removing carbon dioxide from the body. **Systemic circulation:** - It is the movement of blood from the heart to the rest of the body and back to the heart. - The blood delivers oxygen and nutrients to the body tissues and removes carbon dioxide and waste products. - It is responsible for delivering oxygen and nutrients to the tissues, removing waste products from the tissues, and regulating body temperature.