Chapter 3- Cells, Tissues and Body Organization PDF

Dr. Lina Al Kury Chapter 3 The cells, tissues and organization of the body  Learning Outcomes: ¤Part I: Cells and Tissues Describe the structure and function of epithelial, connective, muscular and nervous tissue. ¤Part II: Organization of the body...

Dr. Lina Al Kury Chapter 3 The cells, tissues and organization of the body  Learning Outcomes: ¤Part I: Cells and Tissues Describe the structure and function of epithelial, connective, muscular and nervous tissue. ¤Part II: Organization of the body Define common anatomical terms Identify the principal bones of the axial skeleton and the appendicular skeleton. State the boundaries of the four body cavities and list the contents of each cavity. Compare between benign and malignant tumors. I. Cells and tissues The simple cell Cell structure: 1. Cell membrane (plasma membrane): Phospholipid bilayer Selectively permeable Scattered protein molecules are either surface proteins or wholly embedded in the phospholipid bilayer. Functions of membrane proteins: a. Channels (carriers) involved in the passage of molecules through the membrane. b. Enzymes that catalyze reactions. c. Receptors for hormones and other chemical messengers. d. Branched carbohydrate molecules attached to the outside of some membrane protein molecules give the cell its immunological identity. The plasma membrane 2. Nucleus control center of the cell. contains the body’s genetic material Genetic info (DNA) is stored here. 3. Cytoplasm Includes everything outside the nucleus and inside the plasma membrane. Compartmentalized with small structures (organelles) that perform special functions.  Tissues Tissue: A group of cells that are similar in structure and function. Human body tissues are grouped into four major types: I. Epithelial (covers body surfaces and lines body cavities) II. Connective (binds and supports body parts) III. Muscular (moves body parts) IV. Nervous (receives stimuli and conducts impulses)  Epithelial tissue ˜ Covering body and lining cavities, hollow organs and tubes. ˜ Functions: 1. Protection from dehydration, chemical and mechanical damage 2. Secretion (glands secrete enzymes, perspiration) 3. Absorption (digestive system absorbs food). Classification is based on : 1. Cell shape: a. Squamous: flattened b. Cuboidal: Cubed c. Columnar: Column shape 2. No. of layers: a. Simple: 1 layer b. Stratified: 2 or more layers (a) Squamous Cuboidal Columnar (b) Simple Stratified Classification of epithelia: (a) on the basis of cell shape (b) on the basis of arrangement (layers) 9 (a) Simple squamous epithelium: Ex. Lining of the alveoli and small blood Vessels (capillaries) (b) Simple cuboidal epithelium: Ex. Lining of kidney tubules (c) Simple columnar epithelium: Ex. Lining of digestive tract (mucus secretion) Ex. Lining of the trachea (Ciliated) 10 (d) Stratified epithelium: Ex. Skin (stratified Squamous) Transitional epithelium Ex. Urinary bladder and Uterus  Connective tissue Most abundant tissue in the body. Has three components a. Matrix (intercellular substance) b. Cells c. Fibers in the matrix support the cells Functions: 1. Binding and structural support 2. Protection 3. Transport 4. Insulation ˜ Fibroblasts: produce collagen and elastic fibers. ˜ Fat cells (adipocytes). ˜ Macrophages (defense mechanisms). ˜ White blood cells. I. Fibrous connective tissue Collagen fibers: give hardness Elastic fibers: give elasticity (stretchy) a. Loose (areolar) connective tissue It is the most a widely distributed type of connective tissue. Its presence in lungs, arteries and the urinary bladder allows these organs to expand. b. Dense connective tissue Composed of large number of fibers. Found in: - Tendons (connect muscle to bone): large number of collagen fibers. - Ligaments (connect bone to bone): large number of collagen fibers. - Large blood vessels and trachea: large number of elastic fibers. Loose connective tissue Dense connective tissue 15  II. Supportive connective tissue a. Bone: Composed of bone cells surrounded by layers of very hard matrix that contains calcium and phosphate salts and high no. of collagen fibers. -Two types: compact bone and spongy bone. Function: support and protection (ex. Skull). b. Cartilage: - Less hard and more flexible than bone. - Has abundant collagen fibers. Function: Found in structures that withstand tension and pressure and provide support. (A) Hyaline cartilage (B) Fibrocartilage (C) Elastic cartilage Ex. Ends of long bones, part Ex. Discs between vertebrae Ex. Ear lobe and nose of the larynx, trachea and bronchi III. Adipose tissue It consists of fat cells (adipocytes) Functions: insulation, energy store and organ protection IV. Liquid connective tissue (a) Blood: (discussed later) (b) Lymphoid tissue: important for the immune system. Found in lymph nodes  Muscle tissue ˜ All muscle cells are composed of protein filaments called actin and myosin (Specialized for contraction) ˜ Three types: 1. Skeletal (striated, voluntary): -Has striated cells with multiple nuclei. -Occurs in muscles attached to skeleton -Function: voluntary movement of the body 2. Cardiac (striated, involuntary): -Has branching striated cells, each with a single nucleus. -Occurs in the walls of the heart. -Function: involuntary heart beat. 3. Smooth (nonstriated, involuntary): -Has spindle shaped cells each with a single nucleus. -Occurs in the blood vessel walls and the walls of digestive tract. -Functions: movement of substances in the lumen of the body. 19 Skeletal muscle Smooth muscle Cardiac muscle 20  Nervous tissue Types of cells in nervous tissue: Dendrites (1) Excitable cells called neurons: responsible Cell body for conduction of nerve impulses. Axon (2) Non-excitable cells called glial cells: support and protect neurons. Axon terminal Neuron (nerve cell) is composed of three parts: Dendrite of another neuron 1. Dendrites. 2. Cell body. 3. Axon. 4. Axon terminal. (Discussed later) 21 © 2006 Elsevier Ltd. The skeleton: framework of the body (more later) Axial (80 bones): appendages attached (skull, vertebral column sternum, thoracic cage) Appendicular (126 bones): Shoulders, limbs (upper and lower) General structure of a bone Long bone Short bone  Types of bone 1. Compact bone- solid or dense appearance. Compact bone: 80% of body bone. Made of large number tube-shaped units called (Haversian systems) Central canal of Haversian system is supplied with blood capillaries and nerves. Lamellae: centric rings of bone secreted around the Haversian canals. Lacunae containing osteocytes communicate with each other through a series of tiny channels called canaliculi which allows the circulation of interstitial fluid through the bone. 27 2. Spongy or cancellous bone- spongy appearance. Made of trabeculae (small beams), space in between contains bone marrow Cells of the bone: ˜ 2% of bone is cellular component ˜ Osteoblasts: bone forming cells that secrete collagen ˜ Osteocytes: derived from osteoblasts that stop bone formation ˜ Osteoclasts: result in bone resorption. The skull Functions: 1- Protect delicate structures 2- Maintaining nasal passages 3- Eating- teeth are embedded in the mandible and maxilla  © 2006 Elsevier Ltd. 1 frontal bone 2 parietal bones 2 temporal bones 1 occipital bone 1 sphenoid bone 1 ethmoid bone The vertebral column ˜ 24 movable bones plus sacrum and coccyx. ˜ Bones separated from one another by intervertebral discs (cartilage). ˜ Sacrum consists of 5 vertebrae fused into one. ˜ Coccyx consists of 4 terminal vertebrae fused into a small triangular bone. Functions: 1- Protect the spinal cord, forming a canal in which the spinal cord is held 2- Spinal nerves are protected. 3- Intervertebral discs act as shock absorbers. Cervical vertebra Thoracic vertebra © 2006 Elsevier Ltd. Lumber vertebra The sacrum and coccyx Lower cervical vertebrae are separated to show the spinal cord and spinal nerves emerging through the intervertebral foramina Functions of thoracic cage: 1- Protect thoracic organs (heart, lungs) 2- Attachment for the intercostal muscles 3- Forms joints between upper limbs and axial skeleton Appendicular skeleton 1- The shoulder girdles (clavicle and scapula) and upper limbs (see general figure) 2- The pelvic girdle and lower limbs Functions of appendicular skeleton 1- Voluntary movement 2- Protection of delicate structures (blood vessels, nerves running the length of bones Cavities of the body 1- Cranial cavity 2- Thoracic cavity 3- Abdominal cavity (largest cavity) 4- pelvic cavity Thoracic cavity Organs of the posterior part of the abdominal cavity Organs in the anterior part of the abdominal cavity © 2006 Elsevier Ltd.  A tumor or neoplasm is a mass of tissue that grows faster than normal in an uncoordinated manner and continues to grow after the initial stimulus has ceased.  Causes of tumors (carcinogens): genetic and/or environmental 1. Chemical carcinogens 2. Irradiations 3. Viruses 4. Host factors  In benign tumors: -The cells are well-differentiated (similar shape, functions and genetic make up as parent cell). -Cells are usually encapsulated. In Malignant tumor: - Cells show varying levels of organization. Cells may be poorly differentiated, may lose most of their normal features and parent cells cannot be differentiated. - Cells are usually not encapsulated.  Causes of death in malignant disease: -Infection (Depression of immune system) -Organ failure -Hemorrhage (rupture of the walls of veins and arteries)