The pericardium is a double-walled membranous sac that encloses the heart and contains pericardial fluid, which reduces friction during heartbeats and protects the heart from mechanical injury.
Topics
Reproduction in Lower and Higher Plants
- Reproduction
- Asexual Reproduction
- Asexual Reproduction in Unicellular Organisms > Binary Fission
- Binary Fission > Simple Binary Fission
- Binary Fission > Transverse Binary Fission
- Binary Fission > Longitudinal Binary Fission
- Asexual Reproduction in Unicellular Organisms > Multiple Fission
- Asexual Reproduction in Unicellular Organisms > Budding
- Asexual Reproduction in Multicellular Organisms > Fragmentation
- Asexual Reproduction in Multicellular Organisms > Spore Formation
- Vegetative Reproduction or Vegetative Propagation
- Natural Vegetative Propagation
- Artificial Vegetative Propagation
- Sexual Reproduction
- Flower
- Structure and Development of Anther
- Microsporogenesis
- Structure and Development of Male Gametophyte
- Structure and Development of Ovule
- Types of Ovules (Based on Orientation)
- Types of Ovules (Based on Integuments)
- Megasporogenesis
- Development of Female Gametophyte or Embryo Sac
- Pollination
- Autogamy
- Cross-pollination
- Geitonogamy
- Agents and Types of Cross-pollination
- Anemophily
- Hydrophily
- Entomophily
- Ornithophily
- Cheiropteriphily
- Malacophily
- Outbreeding Devices
- Fertilization
- Pollen Pistil Interaction
- Artificial Hybridization or Artificial Fertilization
- Double Fertilization and Triple Fusion
- Endosperm
- Embryo
- Seed and Fruit Development
- Dormancy
- Apomixis
- Parthenocarpy
- Polyembryony
- Overview of Reproduction in Lower and Higher Plants
Reproduction in Lower and Higher Animals
- Reproduction
- Asexual Reproduction
- Asexual Reproduction in Animals > Gemmule Formation
- Asexual Reproduction in Multicellular Organisms > Budding
- Asexual Reproduction in Multicellular Organisms > Regeneration
- Sexual Reproduction
- Human Reproduction
- The Male Reproductive System
- Basic Concept of Testes
- Duct system of Male Reproductive Tract
- Accessory Glands of Male Reproductive System
- Semen (Seminal fluid)
- External Genitalia: Penis
- The Female Reproductive System
- Ovaries
- Female Reproductive Duct System
- External Genitalia: Vulva
- Mammary Glands
- Puberty
- Menstrual Cycle (Ovarian Cycle)
- Major Events of Menstrual Cycle
- Menstrual Hygiene
- Gametogenesis
- Spermatogenesis
- Structure of Sperm
- Oogenesis
- Structure of Secondary Oocyte
- Fertilization in Human
- Embryonic Development in Human
- Fate of Germ Layers in Embryonic Development
- Stem Cells
- Pregnancy in Humans
- Placenta (Growth) in Human
- Parturition (Birth) in Human
- Lactation in Human
- Concept of Reproductive Health
- Birth Control
- Natural Contraceptive Methods
- Artificial Contraceptive Methods
- Amniocentesis
- Sexually Transmitted Diseases (STD) or Sexually Transmitted Infections (STI)
- Infertility
- Assisted Reproductive Technology (ART)
- Overview of Reproduction in Lower and Higher Animals
Inheritance and Variation
- Heredity
- Gregor Johann Mendel – Father of Genetics
- Mendel's Experiments on Inheritance
- Reasons for Mendel's Success
- Genetic Terminology
- Monohybrid Cross
- Dihybrid Cross
- Mendel's Laws > The Law of Dominance
- Mendel's Laws > The Law of Segregation (Law of Purity of Gametes)
- Mendel's Laws > The Law of Independent Assortment
- Back Cross and Test Cross
- Deviations from Mendel’s Findings
- Exceptions to Mendel's Principles > Incomplete Dominance
- Exceptions to Mendel's Principles > Co-Dominance
- Exceptions to Mendel's Principles > Multiple alleles
- Exceptions to Mendel's Principles > Pleiotropy
- Chromosomal Theory of Inheritance
- Chromosomes - The Carriers of Heredity
- Types of Chromosomes
- Linkage and Crossing Over
- Autosomal Inheritance
- Sex Linked Inheritance
- Colour blindness
- Haemophilia
- Sex Determination
- Sex Determination in Humans
- Sex Determination in Birds
- Sex Determination in Honey Bees
- Human Genetic Disorders
- Thalassemia
- Down's syndrome (Mongolian Idiocy)
- Turner's Syndrome
- Klinefelter's Syndrome
- Overview of Inheritance and Variation
Molecular Basis of Inheritance
- Deoxyribonucleic Acid (DNA)
- Griffith’s Experiment
- Avery, McCarty and MacLeod’s Experiment
- The Hershey-Chase Experiment
- Packaging of DNA Helix
- DNA Replication
- Mechanism of DNA Replication
- Semi-Conservative Replication
- Protein Synthesis
- Transcription
- Transcription Unit and the Gene
- Genetic Code
- Characteristics of the Genetic Code
- Mutations and Genetic Code
- tRNA – the Adapter Molecule
- Translation
- Mechanism of Translation
- Regulation of Gene Expression
- Operon Concept
- The Lac Operon
- Genomics
- Human Genome Project
- DNA Fingerprinting
- Overview of Molecular Basis of Inheritance
Origin and Evolution of Life
- Origin of Life on Earth
- Redi's and Louis Pasteur’s Experiment
- Chemical Evolution of Life
- Urey and Miller’s Experiment
- The RNA World
- Organic Evolution
- Darwin’s Theory of Natural Selection (Darwinism)
- Basic Postulates of Darwinism
- Drawbacks and Criticism of Darwinism
- Mutation Theory
- Modern Synthetic Theory of Evolution
- Modern Synthetic Theory of Evolution > Genetic Variations
- Modern Synthetic Theory of Evolution > Natural Selection
- Modern Synthetic Theory of Evolution > Isolation
- Mechanism of Organic Evolution
- Hardy Weinberg’s Principle
- Adaptive Radiation
- Evidences of Organic Evolution
- Evidences of organic evolution > Palaeontology
- Connecting Links
- Homology and Homologous Organs
- Analogy and Analogous Organs
- Vestigial Organs
- Molecular (Genetic) Evidences
- Speciation
- Geological Time Scale
- Human Evolution
- Stages of Human Evolution
- Overview of Origin and Evolution of Life
Plant Water Relation
- Properties of Water
- Water Absorbing Organ
- Water Available to Roots for Absorption
- Diffusion
- Osmosis
- Imbibition
- Osmotic Pressure
- Water Potential (ψ)
- Turgidity and Flaccidity (Plasmolysis)
- Path of Water Across the Root
- Mechanism of Absorption of Water
- Translocation of Water
- Root Pressure Theory (Vital Theory)
- Capillarity Theory (physical force theory)
- Cohesion-Tension Theory (Transpiration pull theory)
- Transport of Mineral Ions
- Transportation of Food and Other Substances
- Concept of Transpiration
- Types of Transpiration > Cuticular Transpiration
- Types of Transpiration > Lenticular Transpiration
- Types of Transpiration > Stomatal Transpiration
- Structure of Stomatal Apparatus
- Significance of Transpiration
- Overview of Plant Water Relation
Plant Growth and Mineral Nutrition
- Plant Growth
- Phases of Plant Growth
- Conditions for Plant Growth
- Plant Growth Rate
- Types of Plant Growth
- Plant Growth Curve
- Differentiation, De-differentiation, Re- Differentiation
- Plant Development
- Plant Plasticity
- Plant Hormones
- Auxins
- Gibberellins
- Cytokinins
- Ethylene
- Abscisic Acid (ABA)
- Photoperiodism
- Vernalization (Yarovization)
- Plant Mineral Nutrition
- Roles of Mineral Elements in Plants
- Minerals Salt Absorption
- Nitrogen Cycle
- Overview of Plant Growth and Mineral Nutrition
Respiration and Circulation
- Respiration
- Gaseous Exchange in plants
- Respiration in Animals
- Human Respiratory System
- Mechanism of Respiration > Breathing
- Mechanism of Respiration > External Respiration
- Mechanism of Respiration > Internal Respiration
- Cellular Respiration
- Regulation of Breathing / Respiration
- Disorders of Respiratory System
- Transportation in Living Organisms
- Circulation in Animals
- Circulatory System Or Blood Vascular System
- Composition of Blood > Cellular Elements: Red Blood Cells (Erythrocytes)
- Composition of Blood > Cellular Elements: White Blood Cells (Leukocytes)
- Composition of Blood > Cellular Elements: Blood Platelets (Thrombocytes)
- Human Heart
- Working Mechanism of Human Heart
- Blood Vessels
- Blood Pressure (B.P.)
- Electrocardiogram (ECG)
- Lymph and Lymphatic System
- Overview of Respiration and Circulation
Control and Co-ordination
- Need for Control and Coordination in Organisms
- Nervous System in Hydra
- Nervous System in Planaria (Flatworm)
- Neural Tissue
- Synapse
- Transmission and Generation of Nerve Impulse
- Central Nervous System (CNS)
- The Human Brain
- The Spinal Cord
- Peripheral Nervous System (PNS)
- Reflex Action
- Autonomic Nervous System (ANS)
- Sensory Receptors
- Human Eye
- Structure of the Eyeball
- Human Ear
- Internal Ear and the Mechanism of Balance
- Disorders of Nervous System
- Human Endocrine System
- Concept of Hormone
- General Properties of Hormones
- Mechanism of Hormone Action
- The Hypothalamus
- Pituitary Gland or Hypophysis Gland
- The Pineal Gland
- Thyroid Gland
- Parathyroid Gland
- Thymus Gland
- Adrenal Gland (Suprarenal Gland)
- Pancreas (Islets of Langerhans)
- Reproductive Glands (Gonads)
- Diffuse Endocrine Glands
- Overview of Control and Co-ordination
Human Health and Diseases
- Health
- The Immune System
- Immunity
- Types of Immunity > Innate Immunity
- Types of Immunity > Acquired Immunity
- Cells of Immune System
- Vaccination and Immunization
- Structure of Antibody
- Formation of Antigen-Antibody Complex
- Blood Transfusion and Blood Groups (ABO and Rh system)
- Disease
- Diseases Caused by Protozoa > Malaria
- Diseases Caused by Protozoa > Amoebiasis (Amoeboic dysentery)
- Diseases Caused by Helminths > Ascariasis
- Diseases Caused by Helminths > Filariasis (Elephantiasis)
- Diseases Caused by Bacteria > Typhoid
- Diseases Caused by Bacteria > Pneumonia
- Diseases Caused by Viruses > Common Cold
- Diseases Caused by Fungi > Ringworm
- Diseases Caused by Viruses > Dengue Fever
- Cancer
- Types of Cancer
- Causes of Cancer
- Organs Commonly Affected by Cancer
- Prevention/Treatment of Cancer
- Acquired Immuno Deficiency Syndrome (AIDS)
- Concept of Adolescence
- Addiction
- Drug Abuse
- Addiction and Dependence
- Effects of Drug and Alcohol Abuse
- Prevention and Control of Drugs and Alcohol Abuse
- Overview of Human Health and Diseases
Human Reproduction
Enhancement of Food Production
- Improvement in Food Production
- Plant Breeding
- Hybridization and its Technique
- Mutation Breeding
- Tissue Culture
- Single Cell Protein (SCP)
- Biofortification
- Animal Husbandry (Livestock)
- Animal Husbandry (Livestock) > Animal Breeding
- Animal Husbandry (Livestock) > Dairy (Livestock) Farm Management
- Animal Husbandry (Livestock) > Poultry Farm Management
- Animal Husbandry (Livestock) > Apiculture (Bee Farming)
- Animal Husbandry (Livestock) > Pisciculture (Fish Farming)
- Animal Husbandry (Livestock) > Sericulture
- Animal Husbandry (Livestock) > Lac Culture
- Microbes in Human Welfare
- Microbes in Industrial Products
- Microbes in Sewage Treatment
- Microbes in Energy Generation
- Microbes as Biocontrol Agents
- Microbes as Biofertilizers
- Microbial Role in Dairy Products
- Overview of Enhancement of Food Production
Biotechnology
- Concept of Biotechnology
- Principles of Processes of Biotechnology
- Technique of Gene Cloning and rDNA Technology
- Methodology for rDNA Technology
- Applications of Biotechnology in Health and Medicine
- Applications of Biotechnology in Agriculture
- Gene Therapy
- Crop Biotechnology > Genetically Modified Organisms (GMOs)
- Transgenic Plants
- Transgenic Animals
- Bioethics
- Effects of Biotechnology on the Environment
- Effects of Biotechnology on Human Health
- Biopatent
- Biopiracy
- Overview of Biotechnology
Organisms and Populations
- Organisms and Their Environment
- Habitat
- Niche
- Habitat Vs Niche
- Climatic Factors > Temperature
- Climatic Factors > Precipitation
- Climatic Factors > Light
- Soil Factors (Edaphic Factors)
- Adaptations
- Population
- Population Age Distribution
- Population Growth
- Population Interactions
- Positive Interactions > Mutualism (Symbiosis)
- Negative Interactions > Competition
- Negative Interactions > Parasitism
- Negative Interactions > Predation
- Positive Interactions > Commensalism
- Overview of Organisms and Populations
Ecosystems and Energy Flow
Biodiversity, Conservation and Environmental Issues
- Biodiversity
- Levels of Biodiversity
- Patterns of Biodiversity
- Importance of Species Diversity to the Ecosystem
- Biodiversity Current Scenario
- Loss of Biodiversity
- Threatened Species
- Conservation of Biodiversity
- Biodiversity Conservation Methods
- Biological Diversity Act, 2002
- Environmental Issues
- Air Pollution
- Effects of Air Pollution
- Major Air Pollutants
- Prevention and Control of Air Pollution
- Noise Pollution
- Water Pollution
- Sources of Water Pollution
- Prevention and Control of Water Pollution
- Solid Waste Management
- Greenhouse Effect
- Global Warming
- Ozone Layer Depletion
- Deforestation and Its Causes
- Mission Harit Maharashtra
- Overview of Biodiversity, Conservation and Environmental Issues
Estimated time: 22 minutes
- Structure of the Heart
- Layers of the Heart Wall
- Chambers of the Heart
- Definition: Pericardium
- Key Points: The Heart
Maharashtra State Board: Class 8
Structure of the Heart
The heart is located almost at the centre of the thoracic cage. It is situated behind the ribs, between the two lungs, and slightly inclined to the left side.
- The size of our heart is approximately equal to one's own fist, and it weighs about 360 grams. It is covered by a double-layered peritoneal membrane.
- A fluid is present between the two membranes, which protects the heart from friction and mechanical shocks.
- The human heart is a muscular organ composed of involuntary cardiac muscles. These muscles contract and relax with a definite rhythm, known as the beating of the heart.
The human heart is a four-chambered muscular organ, about the size and shape of a closed fist. Two-thirds of the heart's mass is positioned to the left of the midline of the body. The heart is enclosed in a pericardial sac, providing protection and support. The sac is lined with the parietal layer of a serous membrane. The visceral layer of this serous membrane forms the epicardium, which is the outer layer of the heart.
Structure of Heart and Blood Circulation
Maharashtra State Board: Class 8
Layers of the Heart Wall
- Epicardium (Outer Layer): The epicardium is the outermost layer of the heart wall. It serves as a protective layer and is made up of connective tissue. It also contains blood vessels and nerves that supply the heart.
- Myocardium (Middle Layer): The myocardium is the thickest and most muscular layer of the heart wall. It is composed of cardiac muscle tissue that contracts to pump blood. This layer is responsible for the heart's powerful beating action.
- Endocardium (Inner Layer): The endocardium is the innermost layer of the heart wall. It is a thin, smooth layer that lines the inside of the heart chambers. It helps to prevent blood from sticking to the heart walls and keeps the heart functioning smoothly.
Maharashtra State Board: Class 8
Chambers of the Heart
The internal cavity of the heart is divided into four chambers:
- Right atrium
- Right ventricle
- Left atrium
- Left ventricle
The atria are the upper, thin-walled chambers of the heart. They receive blood from veins: the right atrium gets deoxygenated blood from the body, and the left atrium gets oxygenated blood from the lungs.
The ventricles are the lower, thick-walled chambers of the heart. They pump blood forcefully: the right ventricle sends deoxygenated blood to the lungs, and the left ventricle pumps oxygenated blood to the entire body.
The thickness of the chamber walls varies because thicker walls (more myocardium) are needed to generate more force for pumping blood.
CISCE: Class 10
Definition: Pericardium
Maharashtra State Board: Class 12
Heart Valves
| Valve | Location |
|---|---|
| Tricuspid | Right atrium → Right ventricle |
| Bicuspid/Mitral | Left atrium → Left ventricle |
| Semilunar | Pulmonary artery & Aorta |
| Eustachian | Opening of inferior vena cava |
| Thebesian | Opening of coronary sinus → Right atrium |
Maharashtra State Board: Class 12
CISCE: Class 10
CISCE: Class 10
Key Points: The Heart
- Heart is conical-shaped, of mesodermal origin, located in mediastinum (between two lungs), tilted slightly to the left. Enclosed in pericardium (a double-walled membrane with pericardial fluid to reduce friction).
- Three layers — Epicardium (outer, protective), Myocardium (middle, contraction/relaxation), Endocardium (inner, protective).
- Four chambers — 2 atria (thin-walled, receiving blood) + 2 ventricles (thick-walled, pumping blood). Left ventricle is the thickest as it pumps blood to the entire body.
- Septa & External Features — Atria separated by inter-atrial septum (has fossa ovalis). Ventricles are separated by the interventricular septum. Atria and ventricles are separated externally by the coronary sulcus. Aorta = ascending → aortic arch → descending.
- Blood Flow & Conducting System — Right ventricle → deoxygenated blood → lungs | Left ventricle → oxygenated blood → body. Heart is myogenic; pacemaker (SA node) → AV node → Bundle of His → Purkinje fibres → coordinated contraction.
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