Anatomy and Physiology Midterms 3PSY-F PDF

ANATOMY AND PHYSIOLOGY MIDTERMS 3PSY-F TOPIC 1: ANATOMY OF THE GENERALIZED CELL In the late 1600s, Robert Hooke was looking through a primitive microscope at some plant tissue – cork. He saw some cube-like structures...

ANATOMY AND PHYSIOLOGY MIDTERMS 3PSY-F TOPIC 1: ANATOMY OF THE GENERALIZED CELL In the late 1600s, Robert Hooke was looking through a primitive microscope at some plant tissue – cork. He saw some cube-like structures that reminded him of the long rows of monk’s rooms (cells) at the monastery, so he named these structures cells. The cell is the basic living unit of all organisms. The simplest organisms consist of single cells, whereas humans are composed of trillions of cells. An average-sized cell is one fifth the size of the smallest dot you can make on a sheet of paper with a sharp pencil. In spite of their extremely small size, cells are complex living structures. Cells of the human body have many characteristics in common. However, most cells are also specialized to perform specific functions. The human body is made up of many populations of theses specialized cells. The coordinated functions of these populations are critical for complex organisms, such as humans, to survive. The study of cells is an important link between the study of chemistry and tissues. Knowledge of chemistry makes it possible to understand cells because cells are composed of chemicals responsible for many of the characteristics of cells. If we chemically analyze cells, we find that they are made up primarily of four elements – carbon, oxygen, hydrogen, and nitrogen - plus much smaller amounts of several other elements (such as iron, sodium, and potassium). Cells also vary dramatically in the functions, or roles, they play in the body. For example, white blood cells wander freely through the body tissues and protect the body by destroying bacteria and other foreign substances. Some cells make hormones or chemicals that regulate other body cells. Still others take part in gas exchange in the lungs or cleanse the blood (kidney tubule cells). A. ANATOMY OF THE GENERALIZED CELL Although no one cell type is exactly like all others, cells do have the same basic parts, and there are certain functions common to all cells. Each cell is a highly organized unit. Within cells specialized structures called organelles perform specific functions. In general, all cells have three main regions or parts – a nucleus containing the cell’s genetic material and usually located near the center of the cell, cytoplasm – the living material surrounding the nucleus; a semi-fluid cytoplasm which in turn enclosed by the plasma membrane – which forms the outer cell boundary. THE NUCLEUS The control center and the gene-containing nucleus. The genetic material or the deoxyribonucleic acid (DNA) is much like a blue print that contains all the instructions needed for building the whole body. o Human DNA differs from that of a frog. o DNA has the instructions for building proteins. 1  o DNA is also absolutely necessary for cell reproduction A cell that has lost or ejected its nucleus (for whatever reason) is programmed only to die. The shape of the nucleus usually conforms to the shape of the cell. The nucleus has three distinct regions or structures: o The nuclear envelope o Nucleoli o Chromatin Nuclear Envelope The double membrane barrier of the nucleus; in between the two membranes is a fluid-filled “moat” or space. The two layers of the nuclear envelope approach each other and fuse and nuclear pores penetrate through the fused regions. Like other cellular membranes, nuclear envelope is selective permeable, but passage of substances through it is much freer than elsewhere because of large pores. The nuclear membrane encloses a jellylike fluid called nucleoplasm in which the nucleoli and chromatin are suspended. Nucleoli Dark-staining, essentially round bodies in the nucleus. The common sites where ribosomes are assembled o The ribosomes eventually migrate into the cytoplasm, serve as the actual sites of protein synthesis. Chromatin A loose network of bumpy thread of DNA combined with protein when a cell is not dividing. Usually scattered throughout the nucleus When a cell is dividing to form two daughter cells, the chromatin threads coil and condense to form a dense, rod-like bodies called chromosomes. o Chromosomes – much the way a stretched spring becomes shorter and thicker when allowed to relax. THE PLASMA MEMBRANE The flexible plasma membrane is a fragile, transparent barrier that contains the cell contents and separates them from the surrounding environment. Consists of two lipid (fat) layers arranged “tail to tail” in which protein molecules float. Most of the lipid portion is phospholipids and substantial amount of cholesterol is also found in plasma membranes. The olive oil – like lipid bilayer forms the basic “fabric” of the membrane. The polar “heads” of the lollipop-shaped phospholipid molecules are hydrophilic (water loving) and interact with water and other polar molecules. The non-polar “tails” are hydrophobic (“water hating”), the hydrophobic make of the membrane interior that makes the plasma membrane relatively impermeable to most water-soluble molecules. o The cholesterol has a stabilizing effect and helps keep the membrane fluid. 2  o The proteins scattered in the lipid bilayer are responsible for most of the specialized functions of the membrane like enzymes. o The proteins mounted on the cell exterior are receptors, or binding sites for hormones or other chemical messengers. o Most proteins that span the membrane are involved in transport functions, others act as carriers that bind to a substance and move it through the membrane. o Glycoproteins are branching sugar groups that are attached to most of the proteins abutting the extracellular space. ▪ Determine your bloodtype ▪ Act as receptors that certain bacteria, viruses, or toxins can bind to and play a role in cell-to-cell interactions. Specialization of the Plasma Membrane Microvilli and membrane junctions are the most common specializations of the plasma membranes. Commonly displayed by the epithelial cells that form the linings of hollow body organs. Microvilli – “little shaggy hairs” are tiny fingerlike projections that greatly increase the cell’s surface area for absorption so that the process occurs more quickly. The membrane junctions – vary structurally depending on their roles: o Tight junctions are impermeable junctions that bind cells together into leakproof sheets that prevent substances from passing through the extracellular space between cells. o In tight junctions, adjacent plasma membranes fuse together tightly like a zipper. o Example: In small Intestines these junctions prevent digestive enzymes from seeping into the blood stream. THE CYTOPLASM The cellular material outside the nucleus and inside the plasma membrane The site of most cellular activities as factory area of the cell. Believed to be structure less gel during early period, but electron microscope has revealed that it has three major elements: o The cytosol, semi-transparent fluid that suspends the other elements like nutrients which is largely water and a variety of other solutes (dissolved substances) o The organelles are metabolic machinery of the cell, engineered to carry out a specific function for the cell as a whole and synthesized proteins and other package other proteins also. o Inclusions these are chemical substances that may or may not be present, depending on the specific cell type; most inclusions are stored nutrients or cell products including fat droplets common in fat cells, glycogen granules, pigments such as melanin seen in skin and hair cells and other secretory products and various kinds of crystals. CYTOPLASMIC ORGANELLES Literally “little organs” are specialized cellular compartments, each performing its own job to maintain the life of the cell Many organelles are bounded by a membrane similar to the plasma membrane 3  The membrane boundaries of such organelles allow them to maintain an internal environment different from that of the surrounding cytosol. Mitochondria Usually depicted as tiny threadlike or sausage-shaped organelles but in living cells they squirm, lengthen, and change shape almost continuously. Their wall consists of a double membrane, equal to two plasma membranes, placed side by side. The outer membrane is smooth, but the inner membrane has a shelf-like protrusions called cristae (kris’tae). Enzymes dissolved in the fluid within the mitochondria as well as the enzymes that form part of the cristae membranes; carry out the reactions in which oxygen is used to breakdown foods. Known as the “powerhouses” of the cell because when foods are broken down, energy is released and energy is used to form ATP molecules. ATP provides the energy for all cellular work. Metabolically “busy cells”, like liver and muscle cells, use huge amounts of ATP and have hundreds of ATP. Ribosomes These are tiny, round, dark bodies made of proteins and one variety of RNA called ribosomal RNA. Actual sites of protein synthesis in the cell. Floating free in the cytoplasm and others are attached to membranes. When attached to membranes, the whole ribosome-membrane combination is called rough Endoplasmic reticulum. Endoplasmic reticulum Network within a cell System of fluid-filled cisterns (tubules or canals) that coil and twist through the cytoplasm It serves as mini-circulatory system for the cell because it provides a network of channels for carrying substances. In two major forms: o Rough Endoplasmic Reticulum ▪ called because it is studded with ribosomes. ▪ Essential for the building materials of cellular membranes. ▪ Abundant in cells that export protein products like in pancreas cells. o Smooth Endoplasmic Reticulum ▪ Plays no role in protein synthesis ▪ Functions in cholesterol synthesis and breakdown, fat metabolism, and detoxification of drugs. Golgi Apparatus Appears as a stack of flattened membranous sacs associated with swarms of tiny vesicles. Generally found close to the nucleus Acts as the principal “traffic director” for cellular proteins. Its major function is to modify and package proteins (sent to it through it by the rough ER via transport vesicles) 4  Golgi apparatus pinches off sacs containing proteins and phospholipids destined to become part of the plasma membrane. Packages hydrolytic enzymes into membranous sacs called lysosomes that remain in the cell. Lysosomes Literally known as breakdown bodies, which appear in different sizes. These are membrane bags containing powerful digestive enzymes capable of digesting worn-out or non-usable cell structures and most foreign substances that enter the cell. Function as the cell’s demolition sites. Abundant in white blood cells that engulf bacteria and other potentially harmful substances because they rid and digest the body of such foreigners. Homeostatic Imbalance The lysosomal membrane is ordinarily quite stable, but it becomes fragile when the cell is injured or deprived of oxygen and when excessive amounts of Vitamin A are present. Lysosomal rupture results in self-digestion of the cell. Peroxisomes Membranous sacs containing powerful oxidase enzymes that use molecular oxygen to detoxify a number of harmful or poisonous substances including alcohol and formaldehyde. The most important function is to disarm dangerous free radicals – these are highly reactive chemicals with unpaired electrons that can scramble the structure of proteins and nucleic acids. Convert free radicals to hydrogen peroxide (H2O2). The enzyme catalase then converts excess hydrogen peroxide to water. Numerous in livers and kidney cells, which are very active in detoxification. Cytoskeleton An elaborate network of protein structures extends throughout the cytoplasm. Acts as a cell’s “bones and muscles” by furnishing an internal framework that determines cell shape, supports other organelles, and provides the machinery needed for intracellular transport and various types of cellular movements. Made up of microtubules, intermediate filaments and microfilaments. o Intermediate filaments are strong and stable ropelike filaments that help from desmosomes and provide internal guy wires to resists pulling forces on the cell. o Microfilaments such as actin and myosin are most involved in cell motility and in producing changes in cell shape. o Tube-like Microtubules determine the overall shape of a cell and the distribution of organelles. Centrioles Lie close to the nucleus and rod-shaped bodies that lie at right angles to each other. Usually made up of fine microtubules internally. During cell division, the centrioles direct the formation of the mitotic spindle. 5 Other Cell Structures: Cilia Whiplike cellular extensions that move substances along the cell surface. Short hairlike projections of the ciliated cells of the respiratory system lining move mucus up and away from the lungs. Flagella Projections formed by the centrioles that are substantially longer For Example: A flagellated cell in the human body like the sperm, which has a single propulsive flagellum called its tail. TOPIC 2: CELL DIVERSITY CELL DIVERSITY The parts of the cell mentioned have focused on an average human cell. However, the trillion of cells in the human body are made up of 200 different cell types that vary greatly in size, shape, and function. The following are types of the cells according to their specific functions: 1. Cell that connect body parts. Fibroblast The elongated shape of this cell lies along the cable-like fibers that it secretes Has an abundant rough ER and a large Golgi apparatus, to make and secrete the protein building blocks of these fibers. 6 Erythrocytes (RBC) Carries oxygen in the bloodstream Its concave disk shape provides extra surface area for the uptake of oxygen and streamlines the cell so it flows easily through the bloodstream. 2. Cells that cover and line body organs Epithelial Cells The hexagonal shape of this cell is exactly like a “cell” in a honeycomb of a beehive. Allows epithelial cells to pack together in sheets. Has abundant intermediate filaments that resist tearing when the epithelium is rubbed or pulled. 3. Cells that move organs and body parts Skeletal muscle and smooth muscle cells These cells are elongated and filled with abundant contractile filaments, so they can shorten forcefully and move the bones or change the size of internal organs. 4. Cell that stores nutrient Fat Cell The huge spherical shape of a fat cell produced by a large lipid droplet in its cytoplasm. 5. Cell that fights disease Macrophage (a phagocytic cell) Extends long pseudopods (false feet) to crawl through tissue to reach infection sites. The many lysosomes within the cell digest the infectious microorganisms it takes up. 6. Cells that gathers information and controls body functions Nerve Cell (Neuron) Has long processes for receiving messages and transmitting them to other structures in the body. The processes are covered with an extensive plasma membrane and a plentiful rough ER is present to synthesize membrane components. TOPIC 3: THE BODY TISSUES BODY TISSUES What is tissue? What are the different types of body tissues? Epithelial tissue, also referred to as epithelium, refers to the sheets of cells that cover exterior surfaces of the body, lines internal cavities and passageways, and forms certain glands. Connective tissue, as its name implies, binds the cells and organs of the body together and functions in the protection, support, and integration of all parts of the body. Muscle tissue is 7 excitable, responding to stimulation and contracting to provide movement, and occurs as three major types: skeletal (voluntary) muscle, smooth muscle, and cardiac muscle in the heart. Nervous tissue is also excitable, allowing the propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of the body. The next level of the organization is the organ, where several types of tissues come together to form a working unit. Just as knowing the structure and function of cells helps you in your study of tissues, knowledge of tissues will help you understand how organs function. A. EPITHELIAL TISSUE The lining, covering, and glandular tissue of the body The glandular epithelium forms various glands in the body Covering and lining epithelium covers all free body surfaces and contains versatile cells. There are Four major Functions of the Epithelium Tissue 1. It protects underlying tissues Our skin is epithelial tissue and protects us from the harmful rays of the sun and certain chemicals. The lining of our digestive tract is made of epithelial tissue and protects underlying tissue from abrasion as food moves through the tract. 2. It absorbs In the lining of the small intestine nutrients from our digested food enter blood capillaries and get carried to the cells of our body. 3. It secretes All glands are made of epithelial tissue; the endocrine glands secrete hormones, the mucus glands secrete mucus, and our intestinal tract contains cells that secrete digestive enzymes in addition to the pancreas and the liver, which secrete the major portions of digestive enzymes. 4. Epithelial tissue excretes Sweat glands excrete waste products such as urea Special Characteristics of Epithelium Epithelial cells fit closely together to form continuous sheets. Neighboring cells are bound together at many points by cell junctions, including desmosomes and tight junctions. The membranes always have one free (unattached) surface or edge. Apical surface is exposed to the body’s exterior or to the cavity of an internal organ. The lower surface of an epithelium rests on a basement membrane, a structure less material secreted by the cells. Epithelial tissues have no blood supply of their own (avascular) and depend on diffusion from the capillaries in the underlying connective tissue for food and oxygen. If well nourished, epithelial cells regenerate themselves easily. 8 Classifications of Epithelium Classifications of Epithelium are based on the following indications: a. The first classification indicates the relative number of cell layers it has or the cell arrangement. Simple Epithelium – one layer of cells Stratified Epithelium – more than one cell Pseudostratified – arrangement appears to consist of several layers but in, all cells extend from the basement to the outer or free surface of the cells. Transitional – epithelium consist of several layers closely packed, flexible, and easily stretched cells. b. The second describes the shape of its cell. On this basis there are: Squamous cells – flattened like fish scales Cuboidal cells – cube-shaped like dice Columnar cells – shaped like columns c. The term describing the shape and arrangement are then combined. Stratified Epithelia are named for the cells at the free surface of the epithelial membrane, not those resting on the basement membrane. a. SIMPLE EPITHELIA 1. Simple Squamous Epithelium A single layer of thin squamous resting on a basement membrane. The cell fit closely together, much like floor tiles. Forms membranes were filtration or exchange of substances by rapid diffusion. o Air sacs of the lungs o Walls of capillaries o Serous membranes or serosae – the slick membranes that line the ventral body cavity and cover the organs in that cavity. 2. Simple Cuboidal One layer of cuboidal cells resting on a basement membrane. Common in glands and ducts o Salivary glands o Pancreas o Walls of the kidney tubules and covers the surface of the ovaries. 3. Simple Columnar Made up of a single layer of tall cells that fit closely together o Goblet cells, which produce lubricating mucus, are the most seen in this type of epithelium. o Lines the digestive tract from the stomach to the anus Mucosae or mucus membranes are epithelial membranes that line body cavities open to the body exterior. 9 4. Pseudostratified Columnar Epithelium All the cells of pseudostratified rest on a basement membrane. This type of cells is shorter than others, and their nuclei appear at different heights above the basement membrane as a result, this gives rise the false (pseudo) impression that it is stratified. Functions in absorption and secretion. 5. Pseudostratified Ciliated Columnar Epithelium A ciliated variety that lines most of the respiratory tract. The mucus produced by the goblet cells in this epithelium traps dust and other debris and the cilia propel the mucus upward and away from the lungs. b. STRATIFIED EPITHELIUM Consist of two or more cell layers Being considerably more durable than the simple epithelia function primarily to protect. 1. Stratified Squamous Epithelium The most common stratified epithelium in the body. Consists of several layers of cells. The cells at the free edge are squamous. Found in sites that receives a good deal of abuse or friction. o In the esophagus o The mouth o Outer portion of the skin 2. Stratified Cuboidal and Stratified Columnar Epithelia Usually has just two cell layers with atleast the surface cells being cuboidal in shape. The surface cells or stratified columnar epithelium are columnar cells but its basal cells vary in size and shape. Rarely found in the body found mainly in the ducts of large glands 3. Transitional Epithelium Highly modified, stratified squamous epithelium that forms the following: o Lining of the urinary bladder o Lining of the ureters o Part of the urethra Cells of the basal layers are cuboidal or columnar those at the free surface vary in appearance. When the organ is not stretched, the membrane is many layered, and the superficial cells are rounded and domelike. When the organ is distended with urine, the epithelium thins, and the surface cells flatten and become squamous liked. This allows the ureter wall to stretch as a greater volume of urine flows through the tubelike organ. In the bladder, it allows more urine to be stored. 10 4. Glandular Epithelium A gland consists of one or more cells that make and secrete a particular product. Secretion typically contains protein molecules in aquaeous (water-based) fluid. Secretion – is an active process in which the glandular cells obtain needed materials from the blood and use them to make their secretion and then discharge. Two major types of glands: o Endocrine glands lose their connection to the surface (duct); thus they are often called ductless glands. Their secretions (hormones) diffuse directly into the blood vessels. Examples: Thyroid, adrenals and pituitary ▪ Goblets cells are unicellular glands that secrete mucus o Exocrine glands retain their ducts, and their secretions empty through the ducts to the epithelial surface. ▪ Simple Exocrine glands are the sweat glands, most of the glands of the digestive tract and the sebaceous glands. B. CONNECTIVE TISSUE Connects body parts and found everywhere in the body. The most abundant and widely distributed of the tissue types This type of tissue allows movement and provides support for other types of tissue. Matrixes are intercellular material abundant in this tissue and the main sources of difference between the different types of connective tissue. Common Characteristics of Connective Tissue The characteristics of Connective tissue include the following: Variations in blood supply o Most connective tissues are well vascularized (they have good blood supply). o Tendons and ligaments have a poor blood supply and cartilages are avascular. All these structures heal very slowly when injured. 11  Extracellular matrix o Connective tissues are made up of many different types of cell plus varying amounts of a non-living substance found outside the cells, called the extracellular matrix. Types of Connective Tissue All connective tissue consists of living cells surrounded by a matrix. Their major differences reflect fiber type and the number of fibers in the matrix. From most rigid to softest The major connective tissue classes are: o Bone o Cartilage o Dense connective tissue o Loose connective tissue o Blood 1. Bone Sometimes called osseous tissue Composed of bone cells sitting in cavities called lacunae Surrounded by layers of a very hard matrix that contains calcium salts and large numbers of collagen fibers. Has an exceptional ability to protect and support other body organs because of its rock hardness. 2. Cartilage Less hard and more flexible than bone a. Hyaline cartilage o the most widespread and has an abundant collagen fiber hidden by a rubbery matrix with a glassy, blue-white appearance. o Forms the supporting structures of the: o larynx or voice box o Attaches the ribs to the breastbone o Covers the ends of bones where they form joints. o The skeleton of a fetus b. Fibro Cartilage Highly compressible and forms the cushion-like disks o Between the vertebrae of the spinal column. o Pubic symphysis between the pubic bone c. Elastic Cartilage Found where a structure with elasticity is desired o Supports the external ear o Epiglottis o Inside the auditory ear tube 12 3. Dense Connective Tissue Also called dense fibrous tissue that has collagen fibers as its main matrix element. Crowded between the collagen fibers of rows fibroblasts (fiber-forming) that manufacture the fibers. Forms strong, ropelike structures such as tendons and ligaments. a. Tendons Attach skeletal muscles to bones b. Ligaments Connect bones to bones at joints More stretchy and contain more elastic fibers than tendons 4. Loose Connective Tissue These are softer and have more cells and fewer fibers than any other connective tissue except blood. a. Areolar Tissue The most widely distributed connective tissue in the body. Small open place when viewed through a microscope Soft, pliable, “cobwebby” tissue that cushions and protects the body organs it wraps. Functions as a universal packing tissue and connective tissue “glue” because it helps to hold the internal organs together and their proper positions. b. Adipose Tissue Commonly called fat, it is an areolar tissue in which fat cells predominate Forms the subcutaneous tissue beneath the skin, where it insulates the body and protects it from extremes of both heat and cold. Protects some organs individually like: o kidneys are surrounded by a capsule of fat o Adipose tissue cushions the eyeballs in their sockets o Fat “depots” in the body, such as the hips and breasts, where fat is stored and available for fuel if needed. c. Reticular Connective Tissue Consists of a delicate network of interwoven reticular fibers associated with reticular cells, which resemble fibroblasts. It forms the stroma (bed or mattress) or internal supporting framework, which can support many free blood cells (lymphocytes) in lymphoid organs such as lymph nodes, the spleen, and bone marrow. d. Blood or Vascular tissue Considered a connective tissue because it consists of blood cells, surrounded by a nonliving, fluid matrix called blood plasma. Uniquely specialized connective tissue consists of two components: 13  o The formed elements of blood, or the blood cells ▪ The RBC ▪ The WBC ▪ The platelets or thrombocytes o The fluid part of blood or plasma ▪ Plasma is the liquid portion which is 92% water ▪ 7% are proteins, albumin, globulins and fibrinogen The “fibers” of blood are soluble protein molecules that become visible only during blood clotting. The transport vehicle for the cardiovascular system, carrying nutrients, wastes, respiratory gases, and many other substances throughout the body. C. MUSCLE TISSUE These are highly specialized to contract, or shorten, to produce movement These are elongated to provide a long axis for contraction called fibers. Types of Muscle Tissue 1. Skeletal Muscle Packaged by connective tissue sheets into organs called skeletal muscles, which are attached to the skeleton. These types of muscles, can be controlled voluntarily or consciously, form the flesh of the body, the called muscular system. When this cell contracts, they pull on bones or skin; the result of their action is gross body movements or changes in our facial expressions. The cells are long, cylindrical, and multinucleated; they have obvious striations. 2. Cardiac Muscle Found only in the heart; as it contracts, the heart acts as a pump and propels blood through the blood vessels. It has striations, unnucleated, branching cells that fit tightly together at junctions called intercalated disks. Intercalated disks: contain gap junctions that: o Allow ions to pass freely from cell to cell, resulting in rapid conduction of the exciting electrical impulse across the heart. Involuntary control, which means that we cannot consciously control the activity of the heart 3. Smooth Muscle Visceral muscle because no striations are visible. The individual cells have a single nucleus and are spindle-shaped (pointed at each end). Found in the walls of hollow organs such as the stomach, bladder, uterus, and blood vessels. When contracts, the cavity of an organ alternately becomes smaller (constricts) or enlarges (dilates) so that substances are propelled through the organ along a specific pathway. Contracts much more slowly than the other two. Peristalsis, a wavelike motion that keeps food moving through the small intestine, is typical of its activity. 14 D. NERVOUS TISSUE When we think of nervous tissue, we think of cells called neurons All neurons receive and conduct electrochemical impulses from one part of the body to another. Two Major Functional Characteristics irritability conductivity Along with a special group of supporting cells that insulate, support, and protect the delicate neurons. TOPIC 4.1: The Integumentary System FUNCTIONS OF THE INTEGUMENTARY SYSTEM Protection: It guards against pathogens, harmful substances, and UV radiation. Regulation: Helps maintain body temperature through sweat and blood flow. Sensation: Contains sensory receptors for pain, touch, temperature, and pressure. Excretion: Sweat glands remove waste products like urea and salts. Vitamin D Synthesis: Skin cells produce vitamin D when exposed to sunlight. Structure of the Skin Epidermis: The Epidermis, outermost layer, consisting of keratinocytes, melanocytes, Langerhans cells, and Merkel cells. Dermis: The middle layer, rich in blood vessels, nerves, and connective tissue. Houses hair follicles, sweat glands, and sebaceous glands. Hypodermis (Subcutaneous Layer): The deepest layer, composed mainly of fat and connective tissue, providing insulation and cushioning. Accessory Structures 1. Skin: The most significant component that forms a barrier between the body and the external environment. 2. Hair: Provides protection, regulates body temperature, and facilitates the evaporation of sweat. Grows from follicles, offering protection and aiding in sensation. 3. Nails: Protect the tips of fingers and toes from injuries and enhance sensation. Made of keratin, protecting the fingertips and enhancing grip. 4. Glands: Including sweat and sebaceous (oil) glands, which have roles in temperature regulation and lubrication. o Sebaceous Glands: Produce sebum, an oily substance that lubricates skin and hair. o Sweat Glands: Two types— eccrine (widely distributed, regulate temperature) and apocrine (located in armpits and groin, active after puberty). Common Disorders Acne: Caused by clogged pores and bacterial infection. Eczema: Inflammation leading to itchy, red, and cracked skin. Psoriasis: An autoimmune condition causing rapid skin cell turnover. Skin Cancer: Overgrowth of abnormal skin cells, usually due to UV exposure. 15 Maintenance and Care Hygiene: Regular cleaning to prevent infection. Hydration: Keeping the skin moisturized. Protection: Using sunscreen to guard against UV radiation. Interaction with Other Systems Nervous system: Sensory receptors in the skin send signals to the brain. Immune system: The skin acts as a barrier, while Langerhans cells in the epidermis play a role in immune responses. Circulatory system: Blood vessels in the dermis aid in temperature regulation and nourishment of skin cells. TOPIC 4.2: THE CLASSIFICATIONS OF BODY MEMBRANES What are the two classifications of body membranes? The two major categories of body membranes are the epithelial and connective tissues, and these are classified in part according to their tissue makeup. A. EPITHELIAL MEMBRANES The epithelial membranes include the cutaneous membrane (skin), the mucous membranes, and the serous membranes. However, calling these membranes “epithelial” is not only misleading but also inaccurate. Although they all do contain an epithelial sheet, it is always combined with an underlying layer of connective tissue. Hence these membranes are simple organs. 1. Cutaneous Membranes The cutaneous membrane is your skin. Its superficial is composed of a keratinizing stratified squamous epithelium. The underlying dermis is mostly dense (fibrous) connective tissue. Unlike the other epithelial membranes, the cutaneous membrane is exposed to air and is a dry membrane 2. Mucous Membranes A Mucous membrane (mucosa) is composed of epithelium resting on a loose connective tissue membrane called a lamina propia This membrane type lines all body cavities that open the exterior, such as those of hollow organs of the respiratory, digestive, urinary, and reproductive tracts. The term mucosa refers only to the location of the epithelial membranes, not their cell makes up, which varies. However, most mucosae contain either stratified squamous epithelium (mouth and esophagus) or simple columnar epithelium (rest of the digestive system). In all cases, they are “wet,” or moist membranes that are almost continuously bathed in secretions, or in the case of the urinary mucosae, urine. 3. Serous Membranes A serous membrane (serosa) is composed of a layer of simple squamous epithelium resting on a thin layer of areolar connective tissue. In contrast to mucous membranes, which line open body cavities, serous membranes line body cavities that are close to the exterior (except for the dorsal body cavity and joint cavities). 16 Serous membranes occur in pairs. The parietal (parie – wall) layer lines a specific portion of the wall of the ventral body cavity. It folds in on itself to form the visceral layer. Visceral layer which covers the outside of the organs in that cavity The part of the balloon that clings close to your fist can be compared to the visceral serosae clinging to the organ’s external surface. The outer wall of the balloon represents the parietal serosae that lines the walls of the cavity and unlike the balloon, is never exposed but is always fused to the cavity wall. In the body, the serous layers are separated not by air but by a thin, clear fluid, called serous fluid which is secreted by both membranes. Although there is a potential space between the two membranes, they tend to lie very close to each other. The serous fluid: o Allows the organs to slide easily across the cavity walls with one another without friction as they carry out their routine functions. o Such as the pumping heart and a churning stomach are involved. The specific names of the serous membranes depend on their locations: o Peritoneum is the serosae lining the abdominal cavity and covering its organs. o Pleura is the serous membrane that isolate the lungs and o Pericardium is the serous membrane around the heart B. CONNECTIVE TISSUE MEMBRANES Synovial membranes are composed of soft areolar connective tissue and contain no epithelial cells at all. These membranes line the fibrous capsules surrounding joints, when they provide a smooth surface and secrete a lubricating fluid They also line small sacs of connective tissue called bursae and tube-like tendon sheaths. Both of these structures cushion organs moving against each other during muscle activity – such as the movement of a tendon across a bone’s surface. TOPIC 5: The Muscular System The muscular system is responsible for movement, posture, and heat production in the body. It consists of specialized tissues that contract and relax to produce movement. Functions of the Muscular System: Movement: Skeletal muscles work with bones to create movement. Posture Maintenance: Muscles help the body maintain posture and balance. Heat Production: Muscle activity generates heat to maintain body temperature. Protection: Muscles help protect internal organs by acting as a cushion. Types of Muscle Tissue Skeletal Muscle: o Voluntary muscles that are attached to bones and cause body movement. 17 o Striated in appearance (striped under a microscope). o Examples: Biceps, quadriceps, pectoral muscles. Cardiac Muscle: o Involuntary muscle found only in the heart. o Striated like skeletal muscle but with a unique arrangement to allow rhythmic contractions. o Responsible for pumping blood throughout the body. Smooth Muscle: o Involuntary muscle found in the walls of internal organs (e.g., stomach, intestines, blood vessels). o Non-striated and responsible for functions like digestion and blood flow. o Examples: Muscles in the digestive tract, urinary bladder. Structure of Skeletal Muscle Muscle Fiber (Cell): o Each skeletal muscle is made up of muscle fibers, long cylindrical cells containing multiple nuclei. Myofibrils: o Each muscle fiber contains threadlike structures called myofibrils, which are made up of repeating units called sarcomeres. Sarcomeres: o The functional units of muscle contraction, consisting of actin (thin filaments) and myosin (thick filaments). o Sliding Filament Theory: Muscle contraction occurs when myosin heads attach to actin filaments and pull them, causing the sarcomere to shorten. Connective Tissues: o Epimysium: Covers the entire muscle. o Perimysium: Surrounds bundles of muscle fibers (fascicles). o Endomysium: Surrounds individual muscle fibers. Muscle Contraction and Relaxation Neuromuscular Junction: o The point where a motor neuron communicates with a muscle fiber. o The release of acetylcholine (ACh) at the neuromuscular junction triggers muscle contraction. Steps in Muscle Contraction: 1. Impulse Transmission: A nerve impulse travels down a motor neuron to the neuromuscular junction. 18 2. Release of ACh: The motor neuron releases acetylcholine into the synapse, binding to receptors on the muscle fiber. 3. Calcium Release: This triggers the release of calcium ions from the sarcoplasmic reticulum into the muscle fiber. 4. Cross-Bridge Formation: Calcium binds to troponin, causing the myosin heads to attach to actin filaments. 5. Power Stroke: Myosin heads pull the actin filaments inward, shortening the muscle (contraction). Relaxation: o When the nerve signal stops, acetylcholine is broken down, calcium is reabsorbed into the sarcoplasmic reticulum, and the muscle returns to its relaxed state. Types of Muscle Contraction Isotonic Contraction: o The muscle changes length while producing force (e.g., lifting a weight). o Subtypes: Concentric (muscle shortens) and Eccentric (muscle lengthens). Isometric Contraction: o The muscle generates force without changing length (e.g., holding a plank). Interaction with Other Systems Skeletal System: Muscles attach to bones via tendons, and together they create movement. Nervous System: Nerve signals control muscle contractions. Circulatory System: Muscles receive oxygen and nutrients from the blood, and muscle contractions help pump blood, especially during physical activity. Respiratory System: Diaphragm (a skeletal muscle) controls breathing by expanding and contracting the lungs. Common Disorders of the Muscular System Muscular Dystrophy: o A group of genetic disorders causing progressive muscle weakness and loss of muscle mass. o Caused by mutations in genes responsible for healthy muscle function. Myasthenia Gravis: o An autoimmune disorder where antibodies attack acetylcholine receptors, leading to muscle Weakness. 19  Muscle Strains: o Occur when muscles are overstretched or torn, commonly caused by overuse or improper use of muscles. Rhabdomyolysis: o A serious condition in which damaged skeletal muscle breaks down rapidly, leading to the release of muscle fibers into the bloodstream. TOPIC 6: The Skeletal System The skeletal system is the body's framework, composed of bones, cartilage, ligaments, and joints. It serves to support the body, protect internal organs, and enable movement. Functions of the Skeletal System: Support: Provides a rigid framework to maintain body shape. Protection: Protects vital organs (e.g., skull protects the brain, ribs protect the heart and lungs). Movement: Works with the muscular system to facilitate movement. Mineral Storage: Stores essential minerals like calcium and phosphorus. Blood Cell Production: Red and white blood cells are produced in the bone marrow. Energy Storage: Yellow bone marrow stores fat. Classification of Bones Bones are classified into five types based on their shapes: Long bones: e.g., femur, humerus. Provide leverage and movement. Short bones: e.g., carpals, tarsals. Provide stability and support. Flat bones: e.g., skull, ribs. Protect internal organs. Irregular bones: e.g., vertebrae, pelvis. Have complex shapes and functions. Sesamoid bones: e.g., patella. Embedded in tendons to protect them from stress and wear. Bone Structure: Compact bone: Dense outer layer, providing strength and rigidity. Spongy bone: Porous, lightweight inner layer, often housing red bone marrow. Periosteum: A tough outer membrane covering bones. Medullary cavity: Hollow part in long bones filled with yellow bone marrow. Axial vs. Appendicular Skeleton Axial Skeleton: Consists of 80 bones and includes: Skull: Protects the brain and houses sensory organs. Vertebral Column: Protects the spinal cord, supports the body, and provides attachment for ribs and muscles. Rib Cage: Protects the heart and lungs and aids in breathing. Appendicular Skeleton: Consists of 126 bones and includes: 20  Pectoral Girdle: Connects the arms to the body (scapula and clavicle). Upper Limbs: Arms and hands (humerus, radius, ulna, carpals, metacarpals, and phalanges). Pelvic Girdle: Supports the lower limbs (pelvis). Lower Limbs: Legs and feet (femur, tibia, fibula, tarsals, metatarsals, and phalanges). Joints and Their Types Joints (articulations) are where two bones meet, allowing for movement and flexibility. Types of Joints: Fibrous Joints: immovable (e.g., sutures in the skull). Cartilaginous Joints: Partially movable (e.g., vertebral discs). Synovial Joints: Freely movable (e.g., shoulder, knee). These are the most common and contain synovial fluid for lubrication. Subtypes of Synovial Joints: Hinge joint: e.g., elbow and knee. Ball-and-socket joint: e.g., shoulder and hip. Pivot joint: e.g., between the first and second cervical vertebrae. Gliding joint: e.g., wrist and ankle. Saddle joint: e.g., thumb. Ellipsoid joint: e.g., wrist. Bone Growth and Remodeling Ossification (Bone Formation): Begins in utero and continues until early adulthood. Endochondral ossification: Bone develops from cartilage (most bones). Intramembranous ossification: Bone develops from a fibrous membrane (e.g., flat bones of the skull). Bone Growth: Long bones grow at the epiphyseal plates (growth plates) through adolescence. Bone Remodeling: A continuous process where old bone is replaced by new bone. Osteoblasts build new bone, while osteoclasts break down old bone. This process is critical for healing fractures and maintaining bone density. Common Disorders of the Skeletal System 1. Osteoporosis: Characterized by decreased bone density, leading to fragile bones. Often occurs in older adults, especially postmenopausal women. 2. Arthritis: Inflammation of the joints, causing pain and stiffness. 3. Osteoarthritis: Degeneration of cartilage in synovial joints. 4. Rheumatoid arthritis: Autoimmune disease that attacks the joints. Fractures: Breaks in bones due to trauma or weakness. Types: Simple, compound, comminuted, and greenstick fractures. 21