Human Anatomy & Physiology Notes PDF

Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 1 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21...

Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 1 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 2 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 Notes are designed by Bhushan Sir for the Nursing, Pharmacy, Medical, Paramedical & Alternative Therapy Students 3 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 CONTENT 1) Introduction to Human Body 2) The Cellular Level of Organization 3) The Tissue Level of Organization 4) Skeletal & Muscular System 5) Joints 6) Blood & Cardiovascular System 7) Disorders 4 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 CHAPTER 1 INTRODUCTION TO HUMAN BODY 1.1 What are Anatomy and Physiology? Anatomy (ana= up; -tomy tomy = process of cutting) is the science of body structures and the relationships among them. Physiology (physio= nature; -logy logy = study of) is the science of body functions functions—how the body parts work. 1.2 Selected Branches of Anatomy and Physiology BRANCH STUDY OF ANATOMY The first eight weeks of development after fertilization of a Embryology human egg. The complete development of an individual from Developmental biology fertilization to death. Cell biology Cellular structure and functions. Histology Microscopic structure of tissues. Gross anatomy Structures that can be examined without a microscope. Structure of specifi c systems of the body such as the Systemic anatomy nervous or respiratory systems. PHYSIOLOGY Neurophysiology Functional properties of nerve cells. Hormones (chemical regulators in the blood) and how they Endocrinology control body functions. Cardiovascular physiology Functions of the heart and blood vessels. Immunology The body’s defenses against disease-causing causing agents. Respiratory physiology Functions of the air passageways and lungs. Renal physiology Functions of the kidneys. Changes in cell and organ functions due to muscular Exercise physiology activity. Pathophysiology Functional changes associated with disease and aging. Explanation is available on “Bhushan Science” Definition & Scope of Anatomy & Physiology 5 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 1.3 Levels of Structural Organization The human body has different structural levels of organization, starting with atoms molecules and compounds and increasing in size and complexity to cells, tissues, organs and the systems that make up the complete organism. 1.3.1 Atoms molecules and compounds: - At its simplest level, the body is composed of atoms. The most common elements in living organism are carbon, hydrogen, oxygen, nitrogen phosphorus and sulfur. Atoms - Molecule - Compounds 1.3.2 Cell: The smallest independent units of life. All life depends on the many chemical activities of cells. Some of the basic functions of cell are: growth, metabolism, irritability and reproduction. 1.3.3 Tissue: tissue is made up of many similar cells that perform a specific function. The various tissues of the body are divided in to four groups. These are epithelial, connective, nervous and muscle tissue. 1.3.3.1 Epithelial tissue: - Found in the outer layer of skin, lining of organs, blood and lymph vessels and body cavities. 1.3.3.2 Connective tissue: - Connects and supports most part of the body. They constitute most part of skin, bone and tendons. 1.3.3.3 Muscle tissue: - Produces movement through its ability to contract. This constitutes skeletal, smooth and cardiac muscles. 1.3.3.4 Nerve tissue: - Found in the brain, spinal cord and nerves. It responds to various types of stimuli and transmits nerve impulses. 1.3.4 Organ: - Is an integrated collection of two or more kinds of tissue that works together to perform specific function. For example: Stomach is made of all type of tissues 1.3.5 System: Is a group of organs that work together to perform major function. Example: Respiratory system contains several organs. 1.3.6 Organism level: - The various organs of the body form the entire organism. Figure 1. Levels of Structural Organization 6 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 Explanation is available on “Bhushan Science” Levels of Structural Organization 1.4 The Eleven Systems of the Human Body 1) Integumentary System Components:: Skin and associated structures, such as hair, fingernails and toenails, sweat glands, and oil glands. Functions: Protects body; helps regulate body temperature; eliminates some wastes; helps make vitamin D; detects sensations such as touch, pain, warmth, and cold; stores fat and provides insulation. 2) Skeletal System Components: Bones and joints of the body and their associated cartilages. Functions: Supports and protects body; provides surface area for muscle attachments; aids body movements; houses cells that produce blood cells; stores minerals and lipids (fats). 3) Muscular System Components: Specifi cally, skeletal muscle tissue—muscle tissue usually attached to bones (other muscle tissues include smooth and cardiac). Functions: Participates in body movements, such as walking; maintains posture; produces heat. 4) Nervous System Components: Brain, spinal cord, nerves, and special sense organs, such as eyes and ears. Functions: Generates action potentials (nerve impulses) to regulate body activities; detects changes in body’s internal and external environments, interprets changes, and respondsds by causing muscular contractions or glandular secretions. 5) Endocrine System Components: Hormone-producing producing glands (pineal gland, hypothalamus, pituitary gland, thymus, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries, and testes) and hormone-producing producing cells in several other organs. Functions: Regulates body activities by releasing hormones (chemical messengers transported in blood from endocrine gland or tissue to target organ) 7 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 6) Cardiovascular System Components: Blood, heart, and blood vessels. Functions: Heart pumps blood through blood vessels; blood carries oxygen and nutrients to cells and carbon dioxide and wastes away from cells and helps regulate acid–base balance, temperature, and water content of body fl uids; blood components help defend against disease and repair damaged blood vessels. 7) Lymphatic System And Immunity Components: Lymphatic fluid and vessels; spleen, thymus, lymph nodes, and tonsils; cells that carry out immune responses (B cells, T cells, and others). Functions: Returns proteins and fluid to blood; carries lipids from gastrointestinal tract to blood; contains sites of maturation and proliferation of B cells and T cells that protect against disease-causing microbes. 8) Respiratory System Components: Lungs and air passageways such as the pharynx (throat), larynx (voice box), trachea (windpipe), and bronchial tubes leading into and out of lungs. Functions: Transfers oxygen from inhaled air to blood and carbon dioxide from blood to exhaled air; helps regulate acid–base balance of body fluids; air flowing out of lungs through vocal cords produces sounds. 9) Digestive System Components: Organs of gastrointestinal tract, a long tube that includes the mouth, pharynx (throat), esophagus (food tube), stomach, small and large intestines, and anus; also includes accessory organs that assist in digestive processes, such as salivary glands, liver, gallbladder, and pancreas. Functions: Achieves physical and chemical breakdown of food; absorbs nutrients; eliminates solid wastes. 10) Urinary System Components: Kidneys, ureters, urinary bladder, and urethra. Functions: Produces, stores, and eliminates urine; eliminates wastes and regulates volume and chemical composition of blood; helps maintain the acid–base balance of body fluids; maintains body’s mineral balance; helps regulate production of red blood cells. 8 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science  Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 11) Reproductive Systems Components: Gonads (testes in males and ovaries in females) and associated organs (uterine tubes or fallopian tubes, uterus, vagina, and mammary glands in females and epididymis, ductus or vas deferens, seminal vesicles, prostate, and penis in males). Functions: Gonads produce gametes (sperm or oocytes) that unite to form a new organism; gonads also release hormones that regulate reproduction and other body processes; associated organs transport and store gametes; mammary glands produce milk. Explanation is available on “Bhushan Science” The Eleven Systems of the Human Body 1.5 Basic Life Processes Certain processes distinguish organisms, or living things, from nonliving things. Following are the six most important life processes of the human body: Figure 2- Basic Life Processes i. Metabolism is the sum of all chemical processes that occur in the body. Metabolism = Catabolism + Anabolism a) Catabolism,, the breakdown of complex chemical substances into simpler components. b) Anabolism,, the building up of complex chemical substances from smaller, simpler components. 9 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science  Human Anatomy & Physiology Notes By “Bhushan Science” Science Edition 2020 2020-21 ii. Responsiveness or irritability,, is the ability to sense changes (stimuli) in the environment and then to react to them. iii. Movement includes all the activities promoted by the muscular system, such as propelling ourselves from one place to another (by walking, swimming, and so forth) and manipulating the external environment with our fingers. iv. Growth is an increase in size, usually accomplished by an increase in the number of cells. v. Differentiation is the development of a cell from an unspecialized to a specialized state. vi. Reproduction, the production of offspring, can occur on the cellular or organismal level. Explanation is available on “Bhushan Science” Basic Life Processes 1.6 Homeostasis The word homeostasis describes the body’s ability to maintain relatively stable internal conditions even though the outside world is continuously changing. Although the literal translation of homeostasis is “unchanging” (homeo = the same; stasis = standing still), the term does not really mean an unchanging state. Instead, it indicates a dynamic state of equilibrium, or a balance in which internal conditions change and vary but always within relatively na narrow limits. 1.6.1 Homeostatic Controls Homeostasis in the human body is continually being disturbed. Some disruptions come from the external environment in the form of physical insults such as the intense heat of a hot summer day or a lack of enough oxygen for that two-mile two mile run. Other disruptions originate in the internal environment, such as a blood glucose level that falls too low when you skip breakfast. 1.6.1.1 Feedback Systems The body can regulate its internal environment through many feedback systems. A feedback system or feedback loop is a cycle of events in which the status of a body condition is monitored, evaluated, changed, remonitored, reevaluated, and so on. Each monitored variable, such as body temperature, blood pressure, or blood gluc glucose ose level, is termed a controlled condition. Any disruption that changes a controlled condition is called a stimulus. A feedback system includes three basic components: a receptor, a control center, and an effector. a) A receptor is a body structure that moni monitors tors changes in a controlled condition and sends input to a control center. b) A control center in the body, for example, the brain, sets the range of values within which a controlled condition should be maintained (set point), evaluates the input it receive receives from receptors, and generates output commands when they are needed. c) An effector is a body structure that receives output from the control center and produces a response or effect that changes the controlled condition. 10 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science  Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 Figure 3- The elements of a home homeostatic control system There are two types of Feedback Systems i. Negative Feedback System ii. Positive Feedback System i. Negative Feedback System In Negative Feedback System, the net effect of the response to the stimulus is to shut off the original stimulus or reduce its intensity. ii. Positive Feedback System In Positive feedback systems are rare in the body because they tend to increase the original disturbance (stimulus) and to push the variable farth from its original value. Negative Feedback System Positive Feedback System A feedback mechanism resulting in the A feedback mechanism resulting in the amplification or growth of the output inhibition or the slowing down of a process. signals. Breakdown the homeostasis of the system. Always maintain the condition of homeostasis. Less common but occur in specific Occur more often in the body, helping in situations. maintaining various conditions of the body. Eg. Childbirth, blood clotting etc. Eg. Regulation of body temperature, blood pressure & fluid content. Explanation is available on “Bhushan Science” Homeostasis & Feedback System 11 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 1.7 Basic Anatomical Terminologies 1.7.1 Orientation and Directional Terms Term Definition Illustration Example Toward the head end or The forehead is Superior upper part of a structure or the body; superior to the above nose. Away from the head end The navel is Inferior or toward the lower part inferior to the (anterior) of a structure or the body; below breastbone. The breastbone is Ventral Toward or at the front of anterior to (posterior) the body; in front of the spine. The heart is Dorsal Toward or at the backside posterior to the (posterior) of the body; behind breastbone. The heart is Toward or at the midline of the body; Medial medial to the on the inner side of arm. Away from the midline of the body; on The arms are Lateral the outer lateral to the side of chest. The collarbone is Between a more medial intermediate Interme-diate and a more lateral between the structure breastbone and the shoulder. The elbow is proximal to the wrist (meaning Close to the origin of the body part or that the elbow is Proximal the point of attachment of a limb to the closer to the body trunk shoulder or attachment point of the arm than the wrist is). Farther from the origin of a body part The knee is distal Distal or the point of attachment of a limb to to the thigh. the body trunk 12 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 Super-ficial The skin is Toward or at the body (external) superficial to the surface skeleton. The lungs are Away from the body Deep (internal) deep to the rib surface; more internal cage. 1.7.2 Sections  Sagittal Section- s a cut along the lengthwise, or longitudinal, plane of the body, dividing the body into right and left parts.  Median (midsagittal) Section Section-Thehe cut is down the median plane of the body and the right and left parts are equal in size.  Frontal Section- is a cut along a lengthwise plane that divides the body (or an organ) into anterior and posterior parts.  Transverse Section (Cross ross section.) - is a cut along a horizontal plane, dividing the body or organ into superior and inferior parts. 1.7.3 Body Cavities Cavity Comments Cranial cavity Formed by cranial bones and contains brain Vertebral canal Formed by vertebral column Chest cavity; contains pleural and pericardial cavities and the Thoracic cavity mediastinum. A potential space between the layers of the pleura that surrounds a Pleural cavity lung. A potential space between the layers of the pericardium that Pericardial cavity surroun surrounds the heart. Mediastinum Central portion of thoracic cavity between the lungs Abdominopelvic cavity Subdivided into abdominal and pelvic cavities. Contains stomach, spleen, liver, gallbladder, small intestine, and Abdominal cavity most of large intestine Contains urinary bladder, portions of large intestine, and internal Pelvic cavity organs of reproduction Explanation is available on “Bhushan Science” Basic Anatomical Terminologies 13 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 CHAPTER 2 THE CELLULAR LEVEL OF ORGANIZATION 1. Structure and Functions of Cell Cell is the basic living structural and functional unit of the body. Cytology: - It is a branch of science concerned with a study of cells. Cell Theory explains about a) All living organisms are composed of cell and cell products. b) Cell is the basic unit of structure & function of all living organisms. c) All cells come from the division of pre existing cell. d) An organism as a whole can be understood through the collective activities & interactions of its cells. We can divide the cell in to four principal parts: - i. Plasma (cell) membrane: it is the outer lining, limiting membrane separating the cell internal parts from extra cellular materials & external environment. ii. Cytoplasm: cytoplasm is the substance that surrounds organelles and is located between the nucleus and plasma membrane iii. Organelles: these are permanent structures with characteristic morphology that are highly specialized in specific cellular activity. iv. Inclusions: they are the secretions and storage products of cells. Figure 1- Cell 1.1 Cell membrane (Plasma membrane)  Each cell has a limiting boundary, the cell membrane, plasma membrane or plasmalemma.  It is a living membrane, outermost in animal cells.  Plasma membrane maintains the integrity of the cell.  It keeps the cell and its contents separate and distinct from the surrounding.  It is a double layered measuring about 4.5 nm and made of phospholipids, cholesterol, glyco- 14 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 lipid, & carbohydrate (oligosaccharides). (oligosa  The bi-layer is self-sealing. sealing. If a needle is injected and pulled out, it automatically seals.  The plasma membrane is made of proteins and lipids and several models were proposed regarding the arrangement of proteins and lipids. The fluid mosaic model proposed by Singer and Nicholson (1972) is widely accepted. According to the fluid mosaic model,  The plasma membrane is composed of a lipid bilayer of phospholipid molecules into which a variety of globular proteins are embedded.  Each phospholipid molecule has two ends, an outer head hydrophilic i.e. water attracting, and the inner tail pointing centrally hydrophobic, i.e. water repelling.  The protein molecules are arranged in two different ways: proteins these proteins  Peripheral proteins or extrinsic proteins: eins are present on the outer and inner surfaces of lipid bilayer. proteins:: These proteins penetrate lipid bilayer partially or  Integral proteins or intrinsic proteins wholly. Figure 2- Plasma Membrane 1.1.1 Functions  The plasma membrane encloses the cell contents.  It provides cell shape (in animal cells) e.g. the characteristic shape of red blood cells, nerve cells, bone cells, etc  It allows transport of certain substances into and out of the cell but not all substance, so it is termed selectively permeable.  Separate cell from one another.  Provide an abundant surface on which chemical reaction can occur. Explanation is available on Structure & Functions of Plasma “Bhushan Science” Membrane 1.2 THE CYTOPLASM 1.2.1 The Cytoplasm  Cytoplasm is a matrix or ground substance in which various cellular components are found.  It is thick semi transparent, elastic fluid containing suspended particles and a series of minute tubules and filaments that form cytoskeleton. 15 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science Edition 2020 2020-21  Water constitutes 75-90% 90% of the cytoplasm.  It also contains solid components, proteins, carbohydrates, lipids and inorganic substances.  The inorganic components exist as solutions because they are soluble in water.  The majority of organic substances however are found as colloids. Colloids are particles that remain suspended in the surrounding medium. The cytoplasm contains many cell organelles of which we shall learn about :  those that trap and release energy e.g. mitochondria;  those that are secretory or involve involved d in synthesis and transport e.g. Golgi, ribosomes and endoplasmic reticulum  the suicidal bags i.e. lysosomes  the nucleus which controls all activities of the cell, and carries the hereditary material. 1.3 CELL ORGANELLES Organelles are specialized structures ures with characteristic shpes that have specific functions. 1.3.1 Mitochondria Structure  Also called as powerhouse of the cell.cell  Appear as tiny thread like structure under light microscope. Approximately 0.5 - 1.00 µm (micrometer)  Number usually a few hundred to a few thousand per cell.  It is a small, spherical, rod shaped or filamentous structure.  It generates energy.  Each mitochondria posses two membrane, one is smooth (upper) membrane and the other is arranged with series of folds called cristae cristae.  The central cavity of a mitochondrion enclosed by the inner membrane is the matrix.  Wall made of double membrane.  It contains own DNA (circular), RNA’s, ribosomes and enzymes. Function  Oxidises pyruvic acid (breakdown product of glucose) to release energy which gets stored in the from of ATP for ready use. This process is also called cellular respiration.  The most important function of the mitochondria is to produce energy.  Mitochondria help the cells to maintain proper concentration of calcium ions within the compartments of the cell.  The mitochondria also help in building certain parts of blood and hormones like testosterone and estrogen.  The liver cells mitochondria have enzymes that detoxify ammonia.  The mitochondria also play important role in th the e process of apoptosis or programmed cell death.  Play an important role in the fat metabolism. 16 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 Explanation is available on “Bhushan Science” Structure & Functions of Mitochondria Figure 3- Mitochondria 1.3.2 Endoplasmic Reticulum (ER) Structure  It is a network of membranes that form flattened interconnected sacs called as Cisternae are tubular in structure, and form a three three-dimensional polygonal network.  They are frequently associated with ribosomes and special proteins called translocons that ar are necessary for protein translation within the RER.  The phospholipid membrane encloses a space, the lumen from the cytosol, which is continuous with the perinuclear space.  The surface of the rough endoplasmic reticulum is studded with the protein manufactumanufacturing ribosome, which gives it a rough appearance. Hence it is referred as a rough endoplasmic reticulum.  The smooth endoplasmic reticulum consists of tubules, which are located near the cell periphery. This network increases the surface area for the storag storagee of key enzymes and the products of these enzymes.  Rough endoplasmic reticulum synthesizes proteins, while smooth endoplasmic reticulum synthesizes lipids and steroids. It also metabolizes carbohydrates and regulates calcium concentration, drug detoxifica detoxification, tion, and attachment of receptors on cell membrane proteins.  Endoplasmic reticulum varies extensive extending from the cell membrane through the cytoplasm and forming a continuous connection with the nuclear envelope. Functions  They play a vital role in the he synthesis of proteins, lipids, glycogen and other steroids like cholesterol, progesterone, testosterone, etc.  They provide the increased surface area for cellular reactions.  They help in the formation of nuclear membrane during cell division.  They play a vital role in the formation of the skeletal framework. Figure 4- Endoplasmic Reticulum 17 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science Edition 2020 2020-21 Explanation is available on Structure & Functions of Endoplasmic “Bhushan Science” Reticulum 1.3.3 Golgi Body or Golgi Apparatus or Golgi Complex  Golgi apparatus are a series of flat membrane membrane-bound sacs called cisternae.  It having two faces; the convex entry of cis face (faces the rough ER) and the exit or trans face (faces plasma membrane).  The numbers of Golgi apparatus differ according to the cell’s secretion activity.  Golgi apparatus are specialized for receiving the molecules of substances secreted by the endoplasmic reticulum across a group of transporting vesicles.  Then, it classifies and modifies these vesicles and distributes them into the places where they are used in the cell. 1.3.4 Lysosomes (lysis = breaking down; soma = body)  Lysosomes are small, round, membranous vesicles formed by Golgi bodies.  They containin a group of digestive and hydrolytic enzymes (60 kinds).  The lysosomes’ function is to get rid of wornout cells and organelles which no longer have benefits called as autophagy.  Furthermore, lysosomes digest the large molecules of nutrients engulfed by by the cell and change them into structurally simpler substances to enable the cell to benefit from them.  For example, white blood cells use the digestive enzymes present inside the lysosomes to digest and destroy the pathogens which invade the cell.  The cell ell is not affected by the lysosome enzymes because these enzymes are surrounded by a membrane,  Lysosomes are called “suicidal bags” as enzymes contained in them can digest the cell’s own material when damaged or dead called as autolysis. 1.3.5 Ribosome Structure  Situated in two areas of the cytoplasm, few are seen scattered in the cytoplasm and a few are connected to the endoplasmic reticulum.  80S ribosomes respectively comprising of little (40S) and substantial (60S) subunits.  Composed of RNA (rRNA) and ribosomal protein.  Whenever joined to the ER they are called the rough endoplasmic reticulum.  The free and the bound ribosomes are very much alike in structure and are associated with protein synthesis. Figure 5- Ribosome 18 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 Functions  They assemble amino acids to form specific proteins, proteins are essential to carry out cellular activities.  The proteins that are synthesized by the ribosomes present in the cytoplasm are used in the cytoplasm itself. The proteins produced by the bound ribosomes are transported transpo outside the cell. Explanation is available on Structure & Functions of Golgi Body, “Bhushan Science” Lysosomes and Ribosomes 1.3.6 Centriole It is present in all animal cells, located just outside the nucleus. It is cylindrical, 0.5 µm in length and without a membrane. It has 9 sets of peripheral tubules but none in the centre. Each set has three tubules arranged at definite angles. It has its own DNA and RNA and therefore it is self duplicating. Function Centrioles are involved in cell division. They give orientation to the ‘mitotic spindle’ which forms during cell division. 1.3.7 Peroxisomes  They are similar to lysosomes but are smaller and contain several oxidases. Functions  They oxidise amino acid and fatty acid.  They oxidise toxic substances, such as alcohol in liver cells. 1.3.8 Proteasomes  Tiny barrel shaped structures.  Found in nucleus and cytoplasm.  Contains proteases (enzyme that cut the protein into smaller peptides). Functions  They degrade uneeded, damaged or faulty proteins in to smaller peptides. 1.3.9 The Cytoskeleton  It is the network of three types of protein filaments i.e. microfilaments, intermediate filaments and microtubules.  Microfilaments o Thin, composed of protein actin. o Help generate movement and provide mechanical support. o They are involved in muscle contraction, cell division and the cell locomotion. o They anchor the cytoskeleton to integral proteins in the plasma membrane.  Intermediate Filaments o They are thicker than microfilaments. o They provide tensile strength for the cell.  Microtubules o These largest cytoskeletal components are long, composed of protein tubulin. o They help to determine cell shape. o Microtubules also form the spindle fibers for separating chromosomes during mitosis. o When arranged in geometric patterns inside flagella and cilia, they are used for locomotion. 19 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 1.4 NUCLEUS (THE HEREDITARY ORGANELLE) Structure  Nucleus is a membrane bound structure that contains the cell’s hereditary information and controls the cell’s growth and reproduction.  Nucleus is present in all eukaryotic cells, they may be absent in few cells like the mammalian RBCs.  The shape of the nucleus is mostly round, it may be oval, disc shaped depending on the type of cell.  The nuclear envelope is a double membrane that separates the nucleus from the cytoplasm.  All traffic into and out of the nucleus passes through nuclear pores that bridge the double membranes.  The nuclear envelope consists of phospholipids that form a lipid bilayer.  The nuclear envelope is perforated with numerous pores called nuclear pores.  The envelope helps to maintain the shape of the nucleus and assists in regulating the flow of molecules into and out of the nucleus through nuclear pores.  The nuclear envelope is connected with the endoplasmic reticulum (ER) in such a way that the internal compartment of the nuclear envelope is continuous with the lumen of the ER.  Chromosomes consist of DNA, which contains heredity information and instructions for cell growth, development, and reproduction.  When a cell is “resting” i.e. not dividing, the chromosomes are organized into long entangled structures called chromatin and not into individual chromosomes.  Nucleoplasm is the gelatinous substance within the nuclear envelope.  The nucleolus is not surrounded by a membrane, it is a densely stained structure found in the nucleus. Figure 6- A Nucleus Functions of Nucleus  It controls the heredity characteristics of an organism.  It main cellular metabolism through controlling synthesis of particular enzymes.  It is responsible for protein synthesis, cell division, growth and differentiation.  Stores heredity material in the form of deoxy-ribonucleic acid (DNA) strands. Also stores proteins and ribonucleic acid (RNA) in the nucleolus.  It is a site for transcription process in which messenger RNA (mRNA) are produced for protein synthesis.  It helps in exchange of DNA and RNA (heredity materials) between the nucleus and the rest of the cell.  Nucleolus produces ribosomes and are known as protein factories.  It also regulates the integrity of genes and gene expression. 20 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science  Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 Explanation is available on “Bhushan Science” Structure & Functions Nucleus 1.4 Cytoplasmic inclusions Cytoplasmic inclusions are diverse intracellular non-living living substances that are not bound by membranes.. Inclusions are stored nutrients, secretory products, and pigment granules. Examples of inclusions are glycogen granules in the liver and muscle cells, lipid droplets in fat cells, pigment granules in certain cells of skin and hair, and crystals of vario various types. 2. TRANSPORT ACROSS THE CELL MEMBRANE Three types of transport process occur across the membrane. 1. Non-mediated transport 2. Mediated transport 3. Transport in Vesicles 1. Non-mediated transport occurs through the simple diffusion process and the driving force for the transport of a substance through a medium depends on its chemical potential gradient. Thus, the substance diffuses in the direction that eliminates its concent concentration ration gradient; at a rate proportional to the magnitude of this gradient and also depends on its solubility in the membrane’s non-polar core. 2. Mediated transport is classified into two categories depending on the thermodynamics of the system: i. Passive-mediated diffusion:: In this type of process a specific ediated transport or facilitated diffusion molecule flows from high concentration to low concentration. ii. Active transport:: In this type of process a specific molecule is transported from low concentration to high concent concentration, ration, that is, against its concentration gradient. i. Passive mediated transport: Substances that are too large or polar diffuse across the lipid bilayer on their own through membrane proteins called carriers or permeases or channels or transporters transporters. Unlike active transport, this process does not involve chemical energy. energy. So the passive mediated transport is totally dependent upon the permeability nature of cell membrane. Types of passive transport: a) Diffusion  Movement of molecules or ions from an area of hi high gh concentration to an area of lower concentration (down down the concentration gradient).  Until the concentrations of the two regions are equal (Dynamic (Dynamic equilibrium established).  Passive process (No No energy required required)  The differences of concentration between the two regions are termed as concentration gradient.  The rate of diffusion is proportional to the concentration gradient the distance over which the diffusion must occur.  Substances capable of diffusion across the cell surface membrane include 21 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 o Oxygen o carbon dioxide o Steroids o the fat-soluble vitamins (A,D,E,K) o Glycerol o alcohols and o ammonia. b) Facilitated diffusion  The process of the movement of molecules across the cell membrane via special transport proteins that are embedded within the cellular membrane is known as facilitated diffusion or called carrier-mediated diffusion.  Many large molecules, such as glucose, are insoluble in lipids and too large to fit into the porins, therefore, it will bind with its specific carrier proteins, and the complex will then be bonded to a receptor site and moved through the cellular membrane.  Used to transport molecules such as o Glucose o Fructose o non fat-soluble vitamins o urea and o many ions Figure 7- Facilitated Diffusion c) Filtration  Filtration is the process of the movement of water and solute molecules across the cell membrane due to hydrostatic pressure generated by the system.  Depending on the size of the membrane pores, only solutes of a certain size may pass through it.  Example - The membrane pores of the Bowman's capsule in the kidneys are very small, and only albumins (smallest of the proteins) can filter through. On the other hand, the membrane pores of liver cells are extremely large, to allow a variety of solutes to pass through and be metabolized. d) Osmosis  Specialised form of diffusion.  Diffusion of water molecules from an area of high water potential (high concentration) to an area of low water potential (low concentration), through a partially permeable membrane  It is a Passive process.  A cell with a less negative water potential will draw in water but this depends on other factors as well such as solute potential (pressure in the cell e.g. solute molecules) and pressure potential (external pressure e.g. cell wall). 22 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science  Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21  Depending on the condition of the extracellular environment, different things can happen to the cell. If the cell is exposed to an isotonic environment (same concentration inside and outside the cell), the movement of water into and out of the cell occur at the same rate. If the cell is exposed to a hypertonic environment (outside of the cell has higher solute concentration than the inside), the cell will shrivel because of loss of water. If the cell is exposed to a hypotonic environment (inside of the cell has higher concentration than outside), the cell take up more water and becomes bloated and will eventually burst. Figure 8 - Osmosis in Red Blood Cells Explanation is available on “Bhushan Science” Passive Transport ii. Active transport: Active transport is the movement of a substance against its concentration gradient (i.e. from low to high concentration). In this process energy is required. Types of active transport a) Primary active transport:: Primary active transport, also called direct active transport, directly uses energy to transport molecules across a membrane. Example: Sodium-potassium potassium pump, which helps to maintain the cell potential. b) Secondary active transport:: Secondary active transp transport or co-transport, transport, also uses energy to transport molecules across a membrane; however, in contrast to primary active transport, there is no direct coupling of ATP; instead, the electrochemical potential difference created by pumping ions out of the cell is used. The two main forms of active transport are antiport and symport. i. Antiport:: In antiport two species of ion or solutes are pumped in opposite directions across a membrane. One of these species is allowed to flow from high to low concentration which yields the entropic energy to drive the transport of the other solute from a low concentration region to a high one. Example: The sodium-calcium calcium exchanger or antiporter, which allows three sodium ions into the cell to transport one calcium out. ii. Symport: In n antiport two species of ion or solutes are pumped in same directions across a membrane. Symport uses the downhill movement of one solute species from high to low concentration to move another molecule uphill from low concentration to high concentration (against its electrochemical gradient). Example: Glucose symporter, which co-transports co onee glucose (or galactose) molecule into the cell for every two sodium ions it imports into the cell. 23 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science Edition 2020 2020-21 Figure 9- Types of Secondary active transport Explanation is available on “Bhushan Science” Passive Transport iii. Types of Transport in Vesicles a) Endocytosis:: Endocytosis is the process by which cells absorb larger molecules and particles from the surrounding by engulfing them. It is used by most of the cells because large and polar molecules cannot cross the plasma membrane. The material to be internalized rnalized is surrounded by plasma membrane, which then buds off inside the cell to form vesicles containing ingested material. It is of two types i.e. Phagocytosis & Pinocytosis. i. eating is a mechanism whereby the cell can ingest solid particles Phagocytosis or “cell eating,” particles. Phagocytosis is the process by which certain living cells called phagocytes engulf larger solid particles such as bacteria, debris or intact cells. When the solid particle binds to the receptor on the surface of the phagocytic cell, then the pseudopodia extends and later surrounds the particle. Then their membrane fuses to form a large intracellular vesicle called phagosome. These phagosomes fuse with the lysosome, forming phagolysosomes in which ingested material is digested by the action of lysosomal enzymes. During its maturation, some of the internalized membrane is recycled to plasma membrane by receptor mediated endocytosis. ii. drinking,” allows the cell to consume solutions.. An infant’s Pinocytosis, or “cell drinking intestinal lining ingests breast east milk by pinocytosis, allowing the mother’s protective antibodies to enter the baby’s bloodstream. Figure 10- Endocytosis (Phagocytosis & Pinocytosis) b) Exocytosis: The process by which the cells direct the contents of secretory vesicles out of the cell membrane is known as exocytosis. These vesicles contain soluble proteins to be secreted to the extracellular environment, as well as membrane proteins and lipids that are sent to become components of the cell membrane. 24 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 Some of the examples include se secretion cretion of proteins like enzymes, peptide hormones and antibodies from cells and release of neurotransmitter from presynaptic neurons. Figure 11 – Exocytosis Explanation is available on “Bhushan Science” Transport in Vesicles Table 11- Transport of Materials into and out of Cells Transport Description Substances transported process PASSIVE Movement of substances down a concentration gradient PROCESSES until equilibrium is reached; do not require cellular energy in the form of ATP Diffusion Movement of molecules or ions down a concentration gradient due to their kinetic energy until they reach equilibrium. Simple diffusion Passive movement of a substance down its Nonpolar, hydrophobic solutes: concentration gradient through the lipid bilayer of the oxygen, carbon dioxide, and nitrogen plasma membrane without withou the help of membrane gases; fatty acids; steroids; and fat- fat transport proteins. soluble vitamins. Polar molecules such as water, urea, and small alcohols Facilitated Passive movement of a substance down its Polar or charged solutes: glucose; diffusion concentration gradient through the lipid bilayer by fructose; galactose; some vitamins; and transmembrane proteins that function as channels or ions such as K+, Cl, Na+, and Ca2+ carriers. Osmosis Passive movement of water molecules across a Solvent: water in living systems. selectively permeable membrane from an area of higher to lower water concentration until equilibrium is reached. ACTIVE Movement of substances against a concentration PROCESSES gradient; requires cellular energy in the form of ATP. Active Transport Active process in which a cell expends energy to move Polar or charged solutes. a substance across the membrane against its concentration gradient by transmembrane proteins that function as carr carriers. Primary active Active process in which a substance moves across the Na+, K+, Ca2+, H+, I-, Cl-, and other transport membrane against its concentration gradient by pumps ions. (carriers) that use energy supplied by hydrolysis of ATP Secondary active Coupled active transport of two substances across the Antiport: Ca2, H out of cells. Symport: transport membrane using energy supplied by a Na or H glucose, amino acids into cells. 25 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science Edition 2020 2020-21 concentration gradient maintained by primary active transport pumps. Antiporters move Na+ (or H+) and another substancee in opposite directions across the membrane; symporters move Na+ (or H+) and another substance in the same direction across the membrane. TRANSPORT IN Active process in which substances move into or out of VESICLES cells in vesicles that bud from plasma membrane; requires energy supplied by ATP Endocytosis Movement of substances into a cell in vesicles. Receptor-mediated Ligand–receptor receptor complexes trigger infolding of a Ligands: transferrin, low-density low endocytosis clathrin-coated coated pit that forms a vesicle containing lipoproteins (LDLs), some vitamins, ligands. certain hormones, and antibodies. Phagocytosis “Cell eating”; movement of a solid particle into a cell Bacteria, viruses, and aged or dead after pseudopods engulf it to form a phagosome. cells. Pincytosis “Cell drinking” allows the cell to consume solutions. An infant’s intestinal lining ingests breast milk by pinocytosis Exocytosis Movement of substances out of a cell in secretory Neurotransmitters, hormones, and vesicles that fuse with the plasma membrane and digestive enzymes. release their contents into the extracellular fl uid. Explanation is available on “Bhushan Science” Transport Across the Cell Membrane 3. CELL DIVISION A single cell divides many times and forms a multicelled organism. Injured tissues are replaced by new cells through cell division. Thus cell division is one of the most important activities in all organisms. Majority of cells in a multicellular lular organism grow and then can divide. But cells like the nerve and muscle cells of animals do not divide. The process of cell division is almost same in all organisms. A cell passes through phases of growth after which are able to duplicate their chrom chromosomes osomes before they divide. These phases in the life of a cell constitute the cell cycle. 3.1 The cell cycle You can use the term mother or parent cell for the cell that undergoes division and the daughter cells for the ones that are the result of this divi division. sion. Before each daughter cell undergoes division, it must grow to the same size as its mother cell. We can distinguish two main phases in the life of a cell. (i) Interphase - Non-dividing dividing period (Growth phase) (ii) M-phase - Dividing phase (M for Mitosis Mitosi or Meiosis) i. Interphase - (Inter = in between) The interval between two successive cell divisions is termed interphase (phase at which the cell is not dividing). It is the longest period in the cell cycle. The interphase is subdivided into three main periods - G1, S and G2. a) G1 (Growth Phase 1 ) Phase i.e. First phase of growth – This is the longest phase. The first phase of interphase and the cell cycle is called G1. During G1, the cell is preparing to replicate DNA by synthesising the mRNAs and protei proteins ns required to execute the future steps. The cell usually grows larger, and some organelles are copied. b) S or synthetic Phase - It comes next. Lot of DNA is (synthesised). During the S phase, all the genetic information in the cell is copied by the process of DNA replication.. This process of 26 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 replication generates sister chromatids, which are identical pairs of chromosomes. These sister chromatids are attached to each other by a centromere. A centromere is a specialised sequence of DNA that links the sister chromatids and is important throughout mitosis. c) G2 (Growth Phase 2) phase - More protein is synthesised in this phase. Cytoplasmic organelles such as mitochondria, golgi bodies get duplicated. Centriole also divides into two centrioles contained in a single centrosome. Figure 12- Cell Cycle ii. M-phase or Dividing phase - Represented by the symbol M (Mitosis or meiosis). Mitosis occurs so that during this period the chromatids separate and form daughter chromosomes. The daughter chromosomes go to daughter nuclei and cytoplasm divides forming two identical daughter cells. Types of cell division There are two kinds of cell division- mitosis and meiosis. 1. Mitosis : Cell division for growth and replacement wherein the two daugher cells are identical and similar to mother cell in all respects. 2. Meiosis : It occurs in the gonads for sexual reproduction to produce gametes. The resultant cells, egg (in female) and sperms (in male), possess half the chromosome number of the parent cell. 1. Mitosis (mitos = thread) Mitosis is divided into 4 phases or stages termed as (i) Prophase (ii) Metaphase (iii) Anaphase (iv) Telophase (These phase refer to the changes taking place in the nucleus.) The nucleus divides first and then the whole cell divides. Division of one nucleus to give two daughter nuclei (karyokinesis). Division of cytoplasm to give two daughter cells (cytokinesis). 27 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 Prophase a) Chromosomes are visible b) Nucleolus and Nuclear envelop disappears. c) Each centromere mpves to an opposite pole of the cell. Metaphase a) chromosomes move, towards the equator of the cell. b) Each chromosome becomes attached to the spindle fibre by centromere. c) The sister chromatids are not yet separated. Anaphase a) Centromeres divide b) Two daughter chromatids separate c) Each chromatid now contains a centromere and is now termed a chromosome. d) Half the number of now chromosomes (daugher chromatids) move toward one pole and the other half to the other pole. e) Cytokinesis begins as the cleavage furrow starts in animal cells. Telophase a) Chromosomes begin to form a chromatin network as in a nucleus. b) New nuclear membrane is formed around each daughter nucleus. c) Nucleolus becomes visible again. Cytokinesis It is the process of the division of cytoplasm into two. It is initiated in the beginning of telophase and is completed by the end of telophase. In an animal cell, invagination of plasma membrane proceeds from the periphery of the cell towards the interior. Siginificance of Mitosis  It is an equational division, and the two daughter cells are identical in all respects. They receive the same number and kind of chromosomes as were in the mother cells.  It is the process by which growth takes place in animals by constantly adding more and more cells.  It also plays a role in repair by growth, example in wound healing, regeneration of damaged parts and replacement of cells lost during normal wear and tear (as the surface cells of the skin or the red blood cells). 28 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 Figure 13- Mitosis 2. Meiosis (meioun = make smaller, sis = action) This division is also known as ‘reduction division’. But why this name? This is because, in this kind of cell division the normal chromosome number of the mother cell is reduced to half in daughter cells. The normal chromosome number in human being is 46 (23 pairs), but as a result of meiosis this number is halved to 23 in daughter cells. Where does it occur? It occurs in reproductive cells, e.g. in the testes of male and in the ovaries of female animals. Why does it occur? In meiosis the chromosome number is reduced to half so that when doubled at fertilisation (zygote formation) during reproduction it once again becomes full or normal. How does meiosis occur? Meiosis is characterized by two successive divisions of the nucleus (meiosis I and II) and cytoplasm, while the chromosomes divide only once. The phases of meiotic division are given in the flow chart drawn here. - The interphase which precedes the onset of meiosis is similar to the interphase which precedes mitosis. At S-phase, the DNA molecule of each chromosome duplicates to give two DNA molecule and hence two chromatids are found in one chromosome. 29 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science  Human Anatomy & Physiology Notes By “Bhushan Science” Science Edition 2020 2020-21 Meiosis-I and meiosis-II II are continuous and have sub-stages. sub A) Meiosis-I Like mitosis, meiosis also consists of four stages; prophase, metaphase, anaphase and telophase. i. Prophase-I The prophase of meiosis-II is much longer as compared to the prophase of mitosis. It is further sub-dividied dividied into the following five sub-stages sub : a) Leptotene (‘leptos’ - thin; ‘tene - thread) The chromosomes become distinct and appear as long and thin threads due to condensation and thickening of chromosomes. Each chromosome consist of two chromatids held together by a centromere but these are not easily visible. b) Zygotene (‘Zygos’-pairing) Similar or homologus chromosomes start pairing from one end. This pairing is known as synapsis. Each pair of homologous chromosomes is called a bivalent. c) Pachytene (‘pachus’ - thick) The chromosome become shorter and thicker due to contraction. Each paired unit called a bivalent consists of four chromatids (hence bivalents are also known as tetrads. Crossing-over over occurs at the end of pachytene i.e. break and exchange of parts (genes) occurs between non-sister chromatid d (chromatids of a homologous pair). The point of interchange and rejoining appears X-shaped X shaped and is known as chiasma or points of crossing over. d) Diplotene (‘Diplous’-double) The homologous chromosomes begin to separate. The two non-sister sister chromatids of a homologous pair remain, attached at one or two points, the chiasmata. It is at the chiasmata that exchange of segments of chromatids (genes) between homologous chromosomes has taken place. The proces of gene exchange is k known as genetic recombination. recombination e) Diakinesis (dia = through, in different directions, kinesis = motion) The homologous chromosomes of a bivalent move apart from each other. Nuclear membrane and nucleolus disappear. Spindle formation is completed. 30 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science  Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 ii. Metaphase-I o The bivalents arrange themselves at the equator. o The spindle fibres are attached at the centromere of the chromosomes. iii. Anaphase-I o The spindle fibres shorten. o The centromeres of homologous chromosomes are pulled along by the spindle fibres towards the opposite poles (no division of centromere). o Thus, half of the chromosome (each with two chromatids) of the parent cell go to one pole and the remaining half to the opposite pole. o Each set of chromosomes that moves to one pole consists of a mixture of paternal and maternal chromosome parts (new gene combination). iv. Telophase-I o The separated chromosomes form nuclei. o The daughter nuclei have half the number of the parent nucleus. The full set of chromosomes of a cell has paired chromosomes or a diploid set (2n). o The daughter cells are now called haploid (n) or having 1 set of chromosomes. o The nucleous reappears and nuclear membrane forms. o The daughter nuclei begin the second meiotic division., B) Second Meiotic Division has the same four stages; (i) Prophase II (ii) Metaphase II (iii) Anaphase II (iv) Telophase II i. Prophase II o The chromosomes shorten and reappear. The two chromatids are attached to the single centromere. o Formation of spindle starts. o Nucleolus and nuclear membrane begin to disappear. ii. Metaphase II o The chromosomes arrange themselves along the equator. o Formation of spindle apparatus is completed. o The centromere of each chromosome is attached to the spindle fibre. iii. Anaphase II o The centromere in each chromosome divides. 31 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science  Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 o The chromatids get their centromore and become daughter chromosomes and begin to move towards the opposite poles. iv Telophase II o On reaching the poles the chromo-somes organize themselves into haploid daughter nuclei. o The nucleolus and the nuclear membrane reappear. C) Cytokinesis  This may occur in two successive stages, once after meiosis I and then after meiosis II, or in some instances it occurs only after meiosis II.  Meiosis results in four haploid cells. Significance of Meiosis i. It helps to maintain constant number of chromosomes in a species undergoing sexual reproduction. ii. Meiosis occurs during gamete formation (gemetogenesis) and reduces the number of chromosomes from diploid (2n) to haploid (n) in the gametes. These haploid gametes fuse to form diploid zygote during fertilization. The diploid zygote develops into a normal diploid individual. iii. Meiosis establishes new combination of characters due to (i) mixing of paternal and maternal chromosomes and (ii) crossing over during prophase I. As a result the progeny inherits the traits of both mother and the father in new gene combinations. 32 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 Figure 14- Meiosis I & Meiosis II Explanation is available on “Bhushan Science” Cell Cycle 33 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 Table 2- Comparision of Mitosis and Meiosis Mitosis Meiosis 1. Cell divides only once 1. There are two cell divisions. First mitotic division and the second meiotic 2. Takes place in somatic cells division. 3. Duration of prophase is short (few 2. Takes place in germ cells. hours) 3. Prophase compartively longer. (takes 4. Prophase simple many days). 4. Prophase complicated having five substages namely leptotene, zygotene, 5. Synapsis does not occur. pachytene, diplotene and diakinesis. 5. Synapsis of homologous chromosomes 6. No exchange of segments during takes place during prophase. prophase between two chromatids 6. Exchange of segments during crossing of chromosomes. over between non sister chromatids of 7. Each chromosome consists of two two homologous chromosomes. chromatids united by a centromere. 7. Each bivalent has four chromatids and 8. Chromosomes are duplicated at the two centromeres. beginning of prophase. 8. In prophase I, chromosomes appear single although DNA replication has 9. In metaphase all the centromeres taken place in interphase I. line up in the same plane. 9. In metaphase I, the centromeres are lined up in two planes which are 10. The metaphasic plate is made up of parallel to one another. duplicated chromosome. 10. The metaphasic plate is made up of 11. Centromere division takes place paired chromosome. during anaphase. 11. No centromere divisions during Anaphase I, centromeres divide only 12. Spindle fibres disappear completely during Anaphase II. in telophase. 12. Spindle fibres do not disappear 13. Reappearance of nucleoli at completely during telophase I. telophase. 13. Nucleoli do not appear in telophase I. 14. The chromosome number does not 14. There is reduction in the chromosome change at the end of mitosis. number from diploid to haploid. 15. The genetic constitution of daughter 15. The genetic constitution of daughter cells is absolutely identical to that of cells is different as compared to the parent cells. parent cells. The daughter cell chromosomes contain a mixture of 16. Mitosis is of shorter duration. maternal and paternal genes. 17. It is the basis of growth and repair. 16. Meiosis is of longer duration. 17. It is basis of maintaining chromosome number in sexual reproduction, as well as for providing variation in the progeny 34 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 CHAPTER 3 THE TISSUE LEVEL OF ORGANIZATION 1. Introduction A tissue is a group of cells that usually have a common origin and function together to carry out specialized activities. Tissues may be hard, semisolid, or even liquid in their consistency, a range exemplified by bone, fat, and blood. Histology (histo- tissue; -logy- study of) is the science that deals with the study of tissues. Animal Tissues Epithetial tissue Connective Tissue Muscular tissue Nervous Tissue (Protection by (Control and covering, secretion, (Binding, support, (Movement and co-ordination) ordination) Absoption) transport) Locomotion) 2. Epithelial Tissue Structural characteristics : The cells forming epithelial tissue – (i) Are closely packed with no intercellular space in between. (ii) Arise from a non-cellular cellular basement membrane. (iii) Not supplied with blood vessels Functions Line the surfaces, help in absorption, secrete, also bear protoplasmic projections such as tthe Cilia. 2.1 Classification of Epithelial Tissue 35 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science  Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 Types of covering and lining epithelial tissue are classified according to two characteristics: i. Arrangement of cells in layers ii. Cell shapes i. Arrangement of cells in layers The cells are arranged in one or more layers on the basis of number of layers of cell they are classified as: a. Simple epithelium is a single layer of cells that functions in diffusion, osmosis, filtration, secretion, or absorption. b. Pseudostratified epithelium (pseudo- false) appears to have multiple layers of cells because the cell nuclei lie at different levels and not all cells reach the apical surface; it is actually a simple epithelium because all its cells rest on the basement membrane. c. Stratified epithelium (Compound epithelium) consists of two or more layers of cells that protect underlying tissues in locations where there is considerable wear and tear. ii. Cell shapes Epithelial cells vary in shape on the basis of shape of cell they are classified as: a. Squamous cells (flat), are thin, which allows for the rapid passage of substances through them. b. Cuboidal cells, are as tall as they are wide and are shaped like cubes. They may have microvilli at their apical surface and function in either secretion or absorption. c. Columnar cells, are much taller than they are wide, like columns, and protect underlying tissues. Their apical surfaces may have cilia or microvilli, and they often are specialized for secretion and absorption. d. Transitional cells, change shape, from squamous to cuboidal and back, as organs such as the urinary bladder stretch (distend) to a larger size and then collapse to a smaller size. Figure 1- Types of Cell in Epithelial Tissue When we combine the two characteristics (arrangements of layers and cell shapes), we come up with the following types of epithelial tissues: 36 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 I. Simple epithelium A. Simple squamous epithelium B. Simple cuboidal epithelium C. Simple columnar epithelium (nonciliated and ciliated) D. Pseudostratified columnar epithelium (nonciliated and ciliated) II. Stratified epithelium A. Stratified squamous epithelium (keratinized, when surface cells are dead and become hardened, and nonkeratinized, when surface cells remain alive)* B. Stratified cuboidal epithelium* C. Stratified columnar epithelium* D. Transitional epithelium Figure 2- Types of Epithelial Tissue A. SIMPLE SQUAMOUS EPITHELIUM Description Simple squamous epithelium is a single layer of flat cells and centrally located nucleus that is flattened and oval or spherical in shape. Location (1) Lines the cardiovascular and lymphatic system. (2) Forms the epithelial layer of serous membranes (peritoneum, pleura, pericardium). (3) Found in air sacs of lungs, glomerular (Bowman’s) capsule of kidneys, inner surface of tympanic membrane (eardrum). Function Present at sites of filtration (such as blood filtration in kidneys) or diffusion (such as diffusion of oxygen into blood vessels of lungs) and at site of secretion in serous membranes. B. SIMPLE CUBOIDAL EPITHELIUM Description Simple cuboidal epithelium is a single layer of cube-shaped cells; round, centrally located nucleus. Location Covers surface of ovary; lines anterior surface of capsule of lens of the eye etc. Function Secretion and absorption. C. NONCILIATED SIMPLE COLUMNAR EPITHELIUM Description Nonciliated simple columnar epithelium is a single layer of nonciliated 37 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 column like cells with oval nuclei near base of cells. Location Lines gastrointestinal tract (from stomach to anus), ducts of many glands, and gallbladder Function Secretion and absorption. D. CILIATED SIMPLE COLUMNAR EPITHELIUM Description A single layer of ciliated columnlike cells with oval nuclei near base of cells. Location Lines some bronchioles (small tubes) of respiratory tract, uterine (fallopian) tubes, uterus etc. Function Cilia prevent moving mucus and foreign particles toward throat. E. PSEUDOSTRATIFIED COLUMNAR EPITHELIUM Description Appears to have several layers because cell nuclei are at various levels. All cells are attached to basement membrane in a single layer, but some cells do not extend to apical surface. When viewed from side, these features give false impression of a multilayered tissue (pseudo=false). Pseudostratified ciliated columnar epithelium contains cells that extend to surface and secrete mucus (goblet cells) or bear cilia. Pseudostratified nonciliated columnar epithelium contains cells without cilia and lacks goblet cells. Location Ciliated variety lines airways of most of upper respiratory tract; nonciliated variety lines larger ducts of many glands, epididymis, and part of male urethra. Function Ciliated variety secretes mucus that traps foreign particles, and cilia sweep away mucus for elimination from body; nonciliated variety functions in absorption and protection. F. STRATIFIED SQUAMOUS EPITHELIUM Description Has two or more layers of cells; cells in apical layer and several layers deep to it are squamous; cells in deeper layers vary from cuboidal to columnar. Keratinized stratified squamous epithelium develops tough layer of keratin in apical layer of cells. Nonkeratinized stratified squamous epithelium does not contain large amounts of keratin in apical layer Location Keratinized variety forms superficial layer of skin; nonkeratinized variety lines wet surfaces (lining of mouth, esophagus, part of epiglottis, part of pharynx, and vagina) and covers tongue. Function Protection against abrasion, water loss, ultraviolet radiation, and foreign invasion. Both types form first line of defense against microbes. G. STRATIFIED CUBOIDAL EPITHELIUM Description Stratified cuboidal epithelium has two or more layers of cells; cells in apical layer are cube-shaped; fairly rare type. Location Ducts of adult sweat glands and esophageal glands, part of male urethra. Function Protection; limited secretion and absorption. H. STRATIFIED COLUMNAR EPITHELIUM Description Basal layers consist of shortened, irregularly shaped cells; only apical layer has 38 Explanations are available on Youtube Channel “Bhushan Science”©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 columnar cells. Location Lines part of urethra; large excretory ducts of some glands, such as esophageal glands; small areas in anal mucous membrane; part of conjunctiva of eye. Function Protection and secretion. I. TRANSITIONAL EPITHELIUM Description Has a variable appearance (transitional). In relaxed or unstretched state, looks like stratified cuboidal epithelium and as tissue is stretched, cells become flatter, giving the appearance of stratified squamous epithelium. Location Lines urinary bladder and portions of ureters and urethra Function Allows urinary organs to stretch and maintain protective lining while holding variable amounts of fluid without rupturing. Explanation is available on “Bhushan Science” Types of Epithelial Tissue 2.2 Glandular Epithelium It is another type of epithelial tissue. A gland may consist of a single cell or a group of cells that secrete substances into ducts (tubes), onto a surface, or into the blood in the absence of ducts. All glands of the body are classified as either endocri endocrine or exocrine. Endocrine Gland- (endo- inside; -crine secretion) The secretions of endocrine glands, called hormones, diffuse directly into the bloodstream without flowing through a duct. duct Exocrine Glands- (exo- outside) The secretions of exocrine glands secrete their products into ducts that empty onto the surface of a covering and lining epithelium such as the skin surface or the lumen of a hollow organ. A. EXOCRINE GLANDS Description Secretions (hormones) enter interstitial fluid and diffuse directly into bloodstream or onto the surface of tissue without flowing through a duct. Location Sweat, oil, and salivary glands (secrete into mouth cavity) and pancreas (secretes into small intes intestine). Function Produce substances such as sweat to help lower body temperature, oil, earwax, saliva, or digestive enzymes. B. ENDOCRINE GLANDS Description Secretory products released into ducts that empty onto surface of a covering and lining epithelium, such as skin surface. Location Pituitary gland, pineal gland, thyroid and parathyroid glands, adrenal glands, pancreas etc. Function Hormones regulate many metabolic and physiological activities to maintain homeostasis. 2.2.1 Classification of Exocrine Glands They are classified by their structure and shape of the secretary portion. According to structural classification they are grouped into: 39 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science Edition 2020 2020-21 a) Unicellular gland:: these are Single celled gland. The best examples are goblet cell in Respiratory, Gastrointestinal & Genitourinary system. b) Multicultural gland:: Found in several different forms By looking in to the secretary portion exocrine glands are grouped into a) Tubular gland:: If the secretary portion of a gland is tubular. b) Acinar gland: If the secretary portion is flask like. C) Tubulo-acinar:: if it contains both tubular & flask shaped secretary portion. Further more if the duct does not branch it is referred as a simple gland and if it branch's it is compound gland. By combining the shape of the secretary portion with the degree of branching of the duct of exocrine glands are classified into - Unicellular - Multi-cellular - Simple Gland (ducts does not branched) o Simple tubular o Simple Coiled tubular o Simple Branched tubular o Simple Acinar o Simple ple Branched Acinar - Compound Gland (ducts ducts are branched) o Compound Tubular o Compound Acinar o Compound Tubulo-acinar acinar Figure 3- Classification of Exocrine Glands 40 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Science” Edition 2020-21 3. Connective Tissue Connective tissue is found throughout the body. It is usually characterized by large amounts of extracellular material that separates cells from one another. Connective tissue consists of two basic elements: i. Extracellular matrix ii. Cells The extracellular material, or extracellular matrix, matrix, has three major components: (1) Protein fibers, (2) Ground substance consisting of nonfibrous protein and other molecules, and (3) Fluid Three types of protein fibers help form most connective tissues. Collagen (glue-producing) producing) fibers, which resemble microscopic ropes, are flexible but resist stretching. Reticular fibers are very fine, short collagen fibers that branch to form a supporting supporting network. Elastic fibers have a structure similar to that of coiled metal bed springs; after being stretched, they can recoil to their original shape. Ground substance is the shapeless background against which cells and collagen fibers can be seen when using a light microscope. Connective tissue cells are named according to their functions. Cells whose names contain the suffix -blast (germ) produce the matrix; cells ending in -cyte (cell) maintain it; and cells ending in --clast (break) break it down for remodeling. 3.1 Classification cation of Connective Tissue Connective tissue proper Loose (fewer fibers, more ground substance) Areolar Adipose Reticular Dense (more fibers, less ground substance) Dense regular connective tissue Dense irregular connective tissue Elastic connective tissue Supporting connective tissue Cartilage (semisolid matrix) Hyaline Fibrocartilage 41 Explanations are available on Youtube Channel “Bhushan Science” Science”©Bhushan ©Bhushan Science Human Anatomy & Physiology Notes By “Bhushan Science” Edition 2020-21 Elastic Bone (solid matrix) Fluid connective tissue Blood A. Loose Connective Tissue The fibers