Skin, Muscles, and Thorax - PDF

Muscles and skin By Dr. Raneen Sweity , Dr Ibraheem AbuAlrub & Dr Muawiya Abu-Rajab  Skin Is the largest organ by weight and surface area. It varies in thickness in different area, thinnest in the eyelids and thickest in the heels. It is function as : Protection: Acts as a barrier agains...

Muscles and skin By Dr. Raneen Sweity , Dr Ibraheem AbuAlrub & Dr Muawiya Abu-Rajab  Skin Is the largest organ by weight and surface area. It varies in thickness in different area, thinnest in the eyelids and thickest in the heels. It is function as : Protection: Acts as a barrier against pathogens, chemicals, radiation and physical injury. Regulation: Helps regulate body temperature through sweat production and blood flow. Sensation: Contains nerve endings that respond to touch, pain, temperature, and pressure. Metabolism: Involved in the synthesis of vitamin D when exposed to sunlight. Immune Defense: Plays a role in the body's immune response. Structure of the Skin It consists of two major layers: Epidermis: outer, thinner layer, consists of epithelial tissue, avascular layer. Dermis: inner, thicker vascular layer. Epidermis The outermost layer, primarily composed of keratinized stratified squamous epithelium. It provides a protective barrier and contains cells like Keratinocytes : the most abundant cell filled with keratin which work as barrier Melanocytes are cells responsible for melanin production ( the pigment of the skin) Langerhans cells which is responsible for immune defense against pathogens Tactile epithelial Least numerous of the epidermal cells and are responsible for detection of touch sensations. Dermis The deeper part of the skin. Composed of dense irregular connective tissue containing collagen and elastic fibers. Has great tensile strength (resists pulling or stretching forces). Has the ability to stretch and recoil easily. It has many cells including fibroblast, macrophages, nerve cells and adipocytes. Blood vessels, nerves, glands, and hair follicles are also embedded in the dermis. Subcutaneous layer- hypodermis Not part of the skin It is situated beneath the dermis It is composed of loose connective tissue and adipose (fat) tissue. It contains collagen and elastin fibers, blood vessels, and nerves. Attaches the skin to the underlying tissues and organs. It play roles in heat isolation, energy storage, anchoring and cushioning the underling structure. The appendages of the skin The nails. Hair follicles. Sebaceous glands. Sweat glands. The nails They are keratinized plates on the dorsal surfaces of the tips of the fingers and toes. The proximal edge of the plate is the root of the nail. The nail folds is folds of skin that surround and overlap the nail (With the exception of the distal edge of the plate) The nail bed is the surface of skin covered by the nail. Hair and Hair Follicles Hairs are distributed in various numbers over the whole surface of the body, except lips, palms of the hand and soles of the feet. Follicles are invaginations of the epidermis into the dermis from which hairs grow out. Hair and Hair Follicles Hair Shaft: This is the visible part of the hair that extends above the skin. It consists of three layers: Hair Follicle: This is the structure beneath the skin that produces hair. It has several components: Sebaceous Gland: Associated with the hair follicle, this gland produces sebum, an oily substance that moisturizes and protects the hair and scalp. Arrector Pili Muscle: A small muscle attached to the hair follicle. When it contracts (often due to cold or fear), it causes the hair to stand up, creating "goosebumps." Hair Bulb: The base of the hair follicle, where hair growth begins. It contains cells that divide and grow to form the hair. Sebaceous Glands They are situated on the undersurface of the follicles and lie within the dermis. Their secretion, the sebum, pour onto the shafts of the hairs. Sebum is an oily material that helps preserve the flexibility of the emerging hair. It also oils the surface epidermis around the mouth of the follicle. Sweat glands They are long, spiral, tubular glands Distributed over the surface of the body, except on the red margins of the lips, the nail beds, and the glans penis and clitoris. The sweat glands are the most deeply penetrating structures of all the epidermal appendages. They are responsible for sweat secretion, which plays major role in human body temperatures regulation and work as defense against pathogens. Types of muscles Skeletal muscle terminology Muscle : special form of connective tissue that have the propriety of contractility. Agonist: The muscle primarily responsible for a specific movement. It contracts to produce the action. Antagonist: The muscle that opposes the action of the agonist. It relaxes when the agonist contracts, allowing smooth movement. Prime mover: Another term for the agonist; it emphasizes the muscle's role as the main force behind a specific movement. Synergist: Muscles that assist the agonist in performing a movement. They help stabilize the joint and enhance the efficiency of the action. Skeletal muscle terminology Origin : is the muscle attachment that moves the least. Usually located proximally. Insertion : is the muscle attachment that moves the most. Usually located distally. The belly : is the fleshy part of the muscle Tendons Aponeurosis : is a flat, sheet-like fibrous tissue that serves a similar function to a tendon but connects muscles to each other or to the parts they move, rather than to bones Main muscles groups- upper limb Muscle Location action Supraspinatus Shoulder Upper limb abduction Infraspinatus Shoulder Lateral rotation of arm Subscapularis Shoulder Medial rotation of arm Teres minor Shoulder Lateral rotation of arm Biceps Arm Elbow flexion Triceps Arm Elbow extension Main muscles groups- lower limb Muscle Location action Pelvic flour muscles pelvic Support rectum, urethra and vagina Iliopsoas Pelvic Hib flexion Gluteus maximus and the Gluteal region and thigh Hib extension hamstring muscles hamstring muscles Thigh Knee flexion Quadriceps femurs Thigh Knee extention Thorax is the region of the body between the neck and the abdomen Superiorly the thorax communicates with the neck and Inferiorly it is separated from the abdomen by the diaphragm. Function is to protects the lungs and heart and affords attachment for the muscles of the thorax, upper extremity, abdomen, and back. Thoracic cavity The cavity of the thorax can be divided into: Mediastinum medially which contains mediastinal structures (heart, main vessels, thymus, lymph nodes…etc ) 2 pleural cavity which contain lungs. The thoracic wall The thoracic wall is formed: Posteriorly by the thoracic part of the vertebral column. Anteriorly by the sternum & costal cartilages. laterally by the ribs & intercostal spaces. Superiorly by the suprapleural membrane. Inferiorly by the diaphragm. Chest wall Skin (dermis and epidermis ) Superficial fascia (subcutaneous tissue): a layer of loose connective tissue that contains blood vessels, fat and nerves. It support overlying tissue and protect the underlying tissue. Respiratory accessory muscles such as serratus anterior. Intercostal Spaces ❑The spaces between the ribs contain three muscles of respiration: The external intercostal : its fibers runs inferomedially (forward and downward). The internal intercostal: its fibers runs inferolaterally (backward and downward). The innermost intercostal muscle its fibers runs inferolaterally (backward and downward).. ❑The intercostal nerves and blood vessels run between the intermediate and deepest layers of muscles They are arranged in the following order from above downward: intercostal vein, intercostal artery, and intercostal nerve (i.e., VAN). Chest wall Endothoracic fascia : it is a layer of loose connective tissue that lays between innermost intercoastal muscle and partial pleura. Pleura It is a sac formed of 2 layers of mesothelium ( special form of epithelium that is composed of single layer of epithelium) Visceral Pleura: This layer directly covers the lungs, following their contours and fissures. Parietal Pleura: This layer lines the inner surface of the chest wall and diaphragm, providing a protective barrier. Pleural Cavity: The space between the visceral and parietal pleura contains a small amount of pleural fluid, which reduces friction between the layers during respiration. Pleura Functions: Lubrication: The pleural fluid allows smooth movement of the lungs during inhalation and exhalation, preventing friction. Pressure Regulation: The pleura help maintain a negative pressure in the pleural cavity, which is crucial for lung expansion. Protection: The pleura provide a barrier against infection and other potential irritants. Cardiovascular System It is composed from heart, blood vessels and blood. The heart works as a pump that pushes blood to the organs, tissues & cells. Blood delivers oxygen and nutrients to every cell and removes the CO2 and waste products made by those cells. Blood is carried from the heart to the rest of the body through arteries, arterioles, and capillaries & is returned to the heart through venules and veins. Heart The heart is muscular organ weighted 250-400 grams. It is pyramidal in shape lies within the pericardium behind the sternum. It is pyramid in shape, it is base is composed of great vessels and pyramidal walls are composed of muscles. It is composed from 4 champers forming 2 separated pumbs. Heart Right atrium is separated from right ventricles by tricuspid valve. Left atrium is separated from left ventricle by the bicuspid valve. Pulmonary valve separate the right ventricle from the pulmonary artery. Aortic valve separate the left ventricle from the aorta. The pericardium A fibro-serous sac that encloses the heart and the roots of the great vessels lies within the middle mediastinum. It restrict excessive movements of the heart & serves as a lubricated container. Heart wall The walls of the heart are composed of: The epicardium which is the serous pericardium covers the heart externally. The Myocardium the cardiac muscle. The endocardium a layer of endothelium that lines internally. Heart valves 1. Tricuspid Valve Location: Between the right atrium and right ventricle. 2. Pulmonary Valve Location: Between the right ventricle and the pulmonary artery. 3. Mitral (Bicuspid) Valve Location: Between the left atrium and left ventricle. 4. Aortic Valve Location: Between the left ventricle and the aorta. Arterial Supply of the Heart The arterial supply of the heart is provided by: The right coronary artery. The left coronary artery. They arise from the ascending aorta immediately above the aortic valve. The coronary arteries and their major branches are distributed over the surface of the heart. Conducting System of the Heart The normal heart contracts rhythmically at 70- 90 beats/minute in the resting adult. The rhythmic contractile process originates spontaneously in the conducting system. The atria contract first and together, followed later by the contractions of both ventricles together. The slight delay in the passage of the impulse from the atria to the ventricles allows time for the atria to empty their blood into the ventricles before the ventricles contract. Major blood vessels Aorta with its major branches (brachiocephalic trunk, left common carotid artery and left subclavian) Pulmonary arteries Superior vena cava Inferior vena cava Pulmonary veins Blood circulation  Lungs They are two organs located within the thoracic cavity. Responsible for gas exchange. Lungs are divided in to lobes and segments. Fissures divides different lobes.  Bronchial Tree Trachea: Divides into the right and left main bronchi at the level of the carina (around the T4-T5 vertebral level). Carina: separates the openings of the right and left main bronchi. Main Bronchi: Branch into lobar bronchi (secondary bronchi)—three on the right and two on the left— corresponding to each lobe. Segmental Bronchi: Further division into tertiary bronchi, each supplying a specific bronchopulmonary segment. Bronchioles: Smaller airways that lack cartilage and lead to the alveolar ducts and alveoli, where gas exchange occurs. Lung lobes and fissures Blood supply Pulmonary Arteries: Carry deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation. Pulmonary Veins: Return oxygenated blood to the left atrium of the heart. Bronchial Arteries: Supply oxygenated blood to the lung tissue itself. Gas exchange