TISSUES

[Audio] Tissues Good day students, I am (A-I ) SIR EARL EUGENE CASTRO, since physical Sir EARL EUGENE CASTRO having a difficulty and doesn't have a voice as of now, What is the reason why do we need to study Tissues ? It is a way of having KNOWLEDGE OF tissue STRUCTURE AND function IS IMPORTANT IN UNDERSTANDING How INDIVIDUAL CELLS ARE ORGANIZED TO ForM tissues A-N-D How tissues ARE ORGANIZED TO ForM ORGANS, ORGAN SYSTEMS, AND THE COMPLETE ORGANISM..

[Audio] Objectives. OBJECTIVES.

[Audio] ✓ Define the anatomy of the tissues; ✓Identify the different types of body tissues ✓Explain the levels of tissue repair..

[Audio] A Tissue (tish′ Ū ) Is A Group Of Cells With Similar Structure And Function That Have Similar Extracellular Substances Located Between Them. When we say tissue is a collection of cells that share a similar structure and perform related functions. These cells work together to carry out specific tasks in the body..

[Audio] The Microscopic Study Of Tissue Structure Is Called Histology (his-tol′ Ō -je; Histo-, Tissue Plus -ology, Study) In study tissue, it is called histology..

[Audio] In order for us to understand an organ, organ system and organism. We must know first the structure and function of tissue.

[Audio] Tissues The Structure of each tissue type is related to its function (Meaning, the shape and size of tissue have a reason and that is related to its function) Disease may be caused by changes in tissues. Every tissues has a corresponding size and shape which also corresponds to their respective reasons, however if they are being disturbed because of disease every may alter. Such as example Rheumatoid Arthritis Rheumatoid arthritis (R-A---) is an autoimmune disease in which the body's immune system mistakenly attacks its own tissues, primarily the synovium, the membrane that lines the joints. Cancer Cancer represents more than 200 different types of malignancies—diseases caused by the uncontrolled and destructive growth of cells. When cancer cells grow unregulated, they can develop into tumors, invade nearby parts of the body and spread throughout the body..

[Audio] Basic Types of Tissues. Basic Types of Tissues.

[Audio] Epithelial Tissue Covers external and internal surfaces throughout the body. Consists almost entirely of cells with very little extracellular material between them. May consist of a single layer of epithelial cells or multiple layers of epithelial cells between the free surface and the basement membrane. Found in different areas Body coverings Body linings Glandular tissue Functions Protection Absorption Filtration Secretion.

[Audio] Epithelial cells Three types of Epithelium (based on shapes): Squamous – cells are flat, scale like. Cuboidal – cells are cube shaped about as wide as they are tall, cube like. Columnar – cells tend to be taller than they are wide Epithelial Tissue: A Closer Look at Cell Shapes Epithelial tissue, a primary tissue type, is composed of sheets of cells that cover body surfaces, line body cavities, and form glands. Based on the shape of their cells, epithelial tissues can be classified into three main types: squamous, cuboidal, and columnar. 1. Squamous Epithelium Characteristics: Flat, scale-like cells. Thin for rapid diffusion. Found in areas where rapid diffusion is necessary. 2. Cuboidal Epithelium Characteristics: Cube-shaped cells. About as wide as they are tall. Involved in secretion and absorption. 3. Columnar Epithelium Characteristics: Taller than they are wide. Often contain cilia or microvilli for increased surface area. Involved in absorption, secretion, and movement of substances. Squamos Cuboidal Columnar Simple Stratified Simple Squamous Epithelium Secretion and absorption Keratinized Non-keratinized Histology Transitional epithelium Desmosomes Hemidesmosomes Epithelial Tissue Endothelium Filtering Absorption Secretion Protection Gap junctions.

[Audio] Classifications of Epithelia: Simple epithelium – consists of single layer of cells, with each cell extending from the basement membrane to free surface Stratified epithelium – consists of more than one layer of cells, but only the basal layer attaches the deepest layer to the basement membrane Free surface or dulo Classifications of Epithelia Based on Number of Layers Epithelial tissues can be further classified based on the number of cell layers. 1. Simple Epithelium Characteristics: Consists of a single (one) layer of cells. Each cell extends from the basement membrane (the underlying connective tissue) to the free surface. Functions: Often involved in absorption, secretion, and filtration. 2. Stratified Epithelium Characteristics: Consists of more than one layer of cells. Only the basal layer (the deepest layer) attaches to the basement membrane. The other layers are stacked on top of each other. Functions: Provides protection against abrasion, wear, and tear..

[Audio] Classifications of Epithelia: Pseudostratified columnar epithelium is a special type of simple epithelium, that appears to be falsely stratified. It consists of one layer of cells, with all the cells attached to the basement membrane. Due to variations in the shape of the cells, the epithelia appears stratified. Free surface or dulo Pseudostratified Columnar Epithelium: A Closer Look Pseudostratified columnar epithelium is indeed a unique type of simple epithelium. Despite its name, it consists of only one layer of cells, all of which are attached to the basement membrane. Why does it appear stratified? Varying cell heights: The cells have different heights, with some reaching the free surface while others do not. This creates the illusion of multiple layers. Cilia: Many pseudostratified columnar epithelia have cilia on their free surface, which can further obscure the single-layer structure. Where is it found? Trachea: The lining of the trachea (windpipe) is a classic example of pseudostratified columnar epithelium. The cilia on these cells help to move mucus and trapped particles out of the respiratory tract. Bronchi: The larger airways leading to the lungs, the bronchi, are also lined with pseudostratified columnar epithelium. Reproductive system: Parts of the male and female reproductive systems, such as the vas deferens and the fallopian tubes, are lined with this tissue. Functions: Ciliary movement: In the respiratory system, cilia help to clear mucus and debris. Absorption: In the reproductive system, pseudostratified columnar epithelium can absorb nutrients or secretions. Secretion: Some cells in this tissue can secrete mucus or other substances. Overall, pseudostratified columnar epithelium is a specialized type of simple epithelium that plays important roles in various body systems..

[Audio] Simple Epithelium Simple Squamous Epithelium Structure: Function Location Single Layer of flat, Often hexagonal cells; the nuclei appear as bumps when viewed in cross section because the cells are so flat Diffusion, filtration, some secretion and some protection against friction Lining of blood vessels Lymphatic vessels Alveoli Kidney tubules Lining of serous membranes (pleural, pericardial, peritoneal) Some substances easily pass through this thin layer of cells, but other substances do not. In the lungs, simple squamous epithelium, allows for gas exchange. In the kidneys, simple squamous epithelium, helps filter wastes from the blood while keeping blood cells inside the blood vessels..

[Audio] Simple Cuboidal Epithelium Structure: Function Location Single layer of cube shape cells, some cells have microvilli or cilia Secretion and absorption Kidney tubules Glands Bronchioles of lungs Surface of the ovaries Simple cuboidal epithelium is a single layer of cube-like cells that carry out active transport, facilitated diffusion, or secretion. They have a greater secretory capacity than simple squamous epithelial cells..

[Audio] Simple Epithelium Simple Columnar Epithelium Structure: Function Location Single layer of tall narrow cells some cells have microvilli or cilia Movement of particles out of the bronchioles of the lungs by ciliated cells, partially responsible for the movement of oocytes through the uterine Secretion Kidney tubules Glands Bronchioles of lungs Uterine tubes Stomach Intestines Gall bladder Simple columnar epithelium is a single layer of tall, thin cells. The large size of these cells enables them to perform complex functions, such as secretion. The simple columnar epithelium of the small intestine produces and secretes mucus and digestive enzymes..

[Audio] Simple Epithelium Pseudostratified Columnar Epithelium Structure: Function Location Single layer of cells; some cells are tall and thin and reach the free surface, The cells are almost always ciliated and are associated with goblet cells that secrete mucus onto free surface Synthesize and secrete mucus onto the free surface Move mucus that contains foreign particles over the surface of the free surface Lining of nasal cavity Nasal sinuses Auditory tubes Pharynx Trachea Bronchi of lungs Pseudostratified columnar epithelium secretes mucus, which covers its free surface. Cilia in the airways move the mucus and accumulated debris toward the throat, where it is swallowed..

[Audio] Stratified Squamous Epithelium Structure: Function Location Several layers of cells that are cuboidal in the basal layer Progressively flattened toward the surface Protects against abrasion Forms a barrier against infection Keratinized outer layer of the skin Non – Keratinized (Mouth, Throat, Larynx, Esophagus, Anus, Vagina, Inferior urethra) Stratified squamous epithelium forms a thick epithelium because it consists of several layers of cells. Though the deepest cells are cuboidal or columnar and are capable of dividing and producing new cells, the naming is based on the shape of the surface cells. There are two types of stratified squamous epithelia: keratinized stratified squamous and nonkeratinized stratified squamous epithelia. The outer layer of the skin is comprised of a keratinized squamous epithelium. The keratin reduces the loss of water from the body. Stratified squamous epithelium of the mouth is a moist nonkeratinized stratified squamous epithelium. This nonkeratinized stratified squamous epithelium provides protection against abrasion and acts as a mechanical barrier. Water, however, can move across it more readily than across the skin (keratinized stratified squamous)..

[Audio] Transitional Epithelium Structure: Function Location Stratified cells that appear cuboidal when the organ or tube is not stretched and squamous when the organ or tube is stretched by fluid Accommodates fluctuations in the volume fluid in an organ or a tube Protects against the caustic effects of urine Lining of urinary bladder, ureter and superior urethra Transitional epithelium is a special type of stratified epithelium that can be greatly stretched. The shape of the cells change as the epithelium is stretched. Transitional epithelium lines cavities that can expand greatly, such as the urinary bladder. It also protects underlying structures, like the urinary bladder, from the caustic effects of urine..

[Audio] Functional Characteristics Epithelial tissues have many functions, including forming a barrier between a free surface and the underlying tissues and secreting, transporting, and absorbing selected molecules. The structure and organization of cells within each epithelial type reflect these functions..

[Audio] Free surfaces Smooth – reduces friction as material moves across it (lined with microvilli or cilia) Endothelium – the lining of the blood vessels is a specialized type of simple squamous epithelium (smooth) Smooth – example blood vessels.

[Audio] Cell Connection Cells have structures that hold one cell to another or to the basement membrane. These structures do 3 things: Mechanically bind the cells together. Helps form a permeability barrier. Provides a mechanism for intercellular communication..

[Audio] Cell Connection Desmosomes (a band) – are mechanical links that bind cells together Hemidesmosomes (modified desmosomes) – also anchor cells to the basement membrane Tight junction – bind adjacent cells together Tight junctions are cell connection structures that form barriers and anchor cells to each other. Structures called adhesion belts are found just below the tight junctions, and help tight junctions anchor epithelial cells to each other. They prevent the passage of materials between epithelial cells because they completely surround each cell. Materials that pass through an epithelial layer with tight junctions must pass through the cells, so those cells regulate what materials can cross. Tight junctions are found in the lining of the intestines..

[Audio] Cell connection Gap junctions – small channels that allow small molecules and ions to pass from one epithelial cell to an adjacent one Most epithelial cells are connected to one another by gap junctions, and researchers believe that molecules or ions moving through the gap junctions act as communication signals to coordinate the activities of the cells..

[Audio] Glands Secretory Organs Composed of epithelium with a supporting network of connective tissue How do glands develop? By infolding or outfolding of epithelium in the embryo Secretory Organs are structures that produce and release substances called secretions. They are typically composed of epithelial tissue, which forms the functional part of the gland, and a supporting network of connective tissue. Gland development occurs during embryonic development. The process involves either infolding or outfolding of epithelial tissue. This means that the epithelial tissue can grow inward (infold) or outward (outfold) to form the gland's structure..

[Audio] If the gland maintains an open contact with the epithelium from which it develop, a duct is present. Exocrine glands – glands with duct Endocrine glands – glands without duct Hormones – cellular products of endocrine glands A hormone is any member of a class of signaling molecules produced by glands in multicellular organisms that are transported by the circulatory system to target distant organs to regulate physiology and behavior. Glands can be classified based on their connection to the epithelium from which they develop. Exocrine glands maintain an open contact with the epithelium, forming a duct that carries their secretions to a specific location. Examples of exocrine glands include sweat glands, salivary glands, and mammary glands. Endocrine glands have no duct and release their secretions directly into the bloodstream. These secretions, called hormones, travel throughout the body to target specific tissues or organs. Examples of endocrine glands include the thyroid gland, pituitary gland, and adrenal glands..

[image] Endocrine vs Exocrine svg.

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[Audio] Nervous tissues Forms the brain, spinal cord and nerves Responsible for coordinating and controlling many body activities Conscious control of skeletal muscles and unconscious regulation of cardiac muscle are all accomplished by nervous tissue Nervous tissue is the primary component of the nervous system. It is responsible for coordinating and controlling various bodily functions. Here are some key functions of nervous tissue: Forms the brain, spinal cord, and nerves: These structures are essential for processing information, transmitting signals, and coordinating responses. Conscious control of skeletal muscles: The nervous system allows us to consciously move our skeletal muscles, such as when walking or lifting objects. Unconscious regulation of cardiac muscle: The nervous system also controls involuntary functions, like heart rate and blood pressure. In summary, nervous tissue plays a crucial role in enabling our bodies to function effectively and respond to both internal and external stimuli..

[Audio] Nervous tissue Nervous Tissue Structure: Function Location A neuron consists of dendrites A cell body and a long axon, glia or support cells surround neuron Neurons transmit information in the form of action potentials Store information Integrate and evaluate data Protect and form specialized sheaths around axons In the brain Spinal cord ganglia A ganglion is a nerve cell cluster or a group of nerve cell bodies located in the autonomic nervous system and sensory system, mostly outside the central nervous system except certain nuclei..

[Audio] Nervous Tissue Dendrite – cell processes (Extensions) dendrites usually receive stimuli leading to electrical changes that either increase or decrease action potentials(Electrical signals) in the neuron's axon Nucleus/neuron – responsible for conducting action potentials Axon – are nerve cell processes (Extensions).

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[Audio] Muscle Tissues Is to contract or shorten, making movements possible Muscle contraction results from contractile proteins located within the muscle cells Function is to produce movement Three types Skeletal muscle Cardiac muscle Smooth muscle Muscle contraction occurs primarily due to the interaction of contractile proteins found within muscle cells. The main proteins involved are actin and myosin. Importance of muscle contraction Movement: Muscle contraction is essential for all forms of movement, from walking and running to more subtle actions like blinking. Posture and Stability: Continuous muscle contractions help maintain posture and stabilize the body. Circulation: Cardiac muscle contractions pump blood throughout the body, delivering oxygen and nutrients..

[Audio] Muscle tissue Skeletal Muscle Structure: Function Location Skeletal muscle cells or fibers appear striated (banded) Cells are large, long and cylindrical with many nuclei Movement of the body under voluntary control Attach to bone or other connective tissue Striated – stripe, marble, smear Identification: Appearance: Striated (striped) appearance due to the arrangement of actin and myosin filaments. Cell Structure: Long, cylindrical, multinucleated fibers. Control: Voluntary control (under conscious control). Function: Responsible for the movement of bones and the body. Facilitates locomotion, posture, and body movements. Contributes to heat production through muscle activity..

[Audio] Muscle tissue Cardiac Muscle Structure: Function Location Cardiac muscle cells are cylindrical and striated and have single nucleus Branched and connected to one another by intercalated disks which contain gap junctions Pumps the blood Under involuntary (Unconscious) control In the heart Striated – stripe, marble, smear Cardiac Muscle Identification: Appearance: Striated, but with a more branched structure compared to skeletal muscle. Cell Structure: Short, branched cells with a single nucleus; connected by intercalated discs. Control: Involuntary control (not under conscious control). Function: Pumps blood throughout the body via the heart. Maintains rhythmic contractions to ensure continuous blood circulation. Regulates heart rate and responds to physiological demands..

[Audio] Muscle tissue Smooth Muscle Structure: Function Location Smooth muscle cells are tapered at each end, are not striated Have single nucleus Regulate the size of the organs Forces fluid through tubes Controls the amount of light entering the eye Produces goosebumps in the skin In hollow organs such as the stomach and the intestines Skin eyes Striated – stripe, marble, smear Identification: Appearance: Non-striated (smooth) appearance. Cell Structure: Spindle-shaped cells with a single nucleus. Control: Involuntary control (not under conscious control). Function: Controls movements within internal organs (for example, digestive tract, blood vessels). Facilitates processes such as digestion, blood flow regulation, and respiratory function. Contracts slowly and can sustain contractions for longer periods compared to skeletal muscle..

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[Audio] Connective Tissues Is a diverse primary tissue type that make up every organ in the body. Connective tissue differs from the other 3 tissue types in that it consist of cells separated from each other by abundant extracellular matrix Connective tissue includes various types such as bone, cartilage, adipose (fat), blood, and tendons, each serving specific roles in the body. Composition: Unlike epithelial, muscle, and nervous tissues, connective tissue consists of cells that are widely spaced apart. This separation is due to the abundant extracellular matrix, which is a network of proteins and substances that provide structural and functional support. Functions: Support and Structure: Connective tissue provides support to organs and helps maintain their shape. Binding: It connects different tissues and organs, facilitating communication and transport within the body. Storage: Some connective tissues store energy (for example, adipose tissue) and nutrients (for example, blood)..

[Audio] Connective tissue Areolar Connective Tissue Structure: Function Location Fine network of fibers with spaces between Loose packing Support Nourishment for the structures with which it is associated Widely distributed throughout the body Substances in which epithelial basement membrane rest Muscles Nerves Attaches skin to underlying tissues Fiber – Bundles of protein Most widely distributed connective tissue Soft, pliable tissue Contains all fiber types Can soak up excess fluid.

[Audio] Connective tissue Adipose Tissue Structure: Function Location Little extracellular matrix surrounding cells Fat cells are so full of lipids that the cytoplasm is pushed to the periphery of the cell Packing material Thermal insulator Energy storage Protection of organs against injury from being bumped or jarred Widely distributed throughout the body Substances in which epithelial basement membrane rest Muscles Nerves Attaches skin to underlying tissues Matrix is an areolar tissue in which fat globules predominate Many cells contain large lipid deposits Functions Insulates the body Protects some organs Serves as a site of fuel storage.

[Audio] Connective tissue Reticular Tissue Structure: Function Location Fine network of reticular fibers irregularly arranged Provides a superstructure for lymphatic and hemopoietic tissues Within lymph nodes Spleen Bone marrow Reticular fibers, reticular fibres or reticulin is a type of fiber in connective tissue composed of type I-I-I collagen secreted by reticular cells. Reticular fibers crosslink to form a fine meshwork (reticulin). The lymphatic system is part of the vascular system and an important part of the immune system, comprising a large network of lymphatic vessels that carry a clear fluid called lymph directionally towards the heart. Hemopoietic cells Function: pluripotential stem cell that give rise to all of the blood cell lines found in the bone marrow. The spleen plays multiple supporting roles in the body. It acts as a filter for blood as part of the immune system. Old red blood cells are recycled in the spleen, and platelets and white blood cells are stored there. The spleen also helps fight certain kinds of bacteria that cause pneumonia and meningitis. Lymph nodes (erroneously called lymph glands) are a part of the lymphatic system, a component of the body's immune system. Swollen lymph nodes may signal an infection. There are several groups of lymph nodes, which are small, bean-shaped, soft nodules of tissue..

[Audio] Connective tissue Dense Regular Collagenous Connective Tissues Structure: Function Location Matrix composed of collagen fibers running in somewhat the same direction in tendons and ligaments Run in several directions in the dermis of the skin and in organs capsules Withstand great pulling forces exerted in the direction of fiber orientation due to great tensile strength and stretch resistance Tendons Ligaments Collagen is the main structural protein in the extracellular space in the various connective tissues in the body. As the main component of connective tissue, it is the most abundant protein in mammals, making 25% to 35% of the whole-body protein content. Dense connective tissue Main matrix element is collagen fibers Cells are fibroblasts Examples Tendon – attach muscle to bone Ligaments – attach bone to bone.

[Audio] Structure: Function Location Matrix composed of collagen fibers running in somewhat the same direction in elastic ligaments Elastic fiber run in connective tissue of blood vessels wall Capable of stretching and recoiling like a rubber band with strength in the direction of fiber orientation Elastic ligaments between the vertebrae and along the dorsal aspect of the neck Vocal cords Blood vessel walls Dense Regular Collagenous Connective Tissue Dense regular collagenous connective tissue is a type of connective tissue characterized by its tightly packed, parallel arrangement of collagen fibers. This arrangement gives the tissue its strength and resilience, making it well-suited for structures that require resistance to tension and pulling forces. Key characteristics: Densely packed collagen fibers: The predominant component is collagen, a protein that forms strong, fibrous strands. Parallel arrangement: The collagen fibers are aligned in a parallel fashion, providing maximum strength in a specific direction. Minimal ground substance: The amount of ground substance (the non-cellular material between cells) is relatively small, allowing for efficient transmission of forces. Examples of locations: Tendons: Connect muscles to bones. Ligaments: Connect bones to other bones. Fascia: Sheets of connective tissue that surround and support muscles and organs. Dermis: The deeper layer of the skin. Functions: Provides structural support: The tissue's strength and resilience enable it to withstand mechanical stress. Facilitates movement: Tendons and ligaments play crucial roles in enabling movement. Protects organs: Fascia provides protection and support for internal organs. Contributes to skin elasticity: The dermis helps maintain skin elasticity and tension. In essence, dense regular collagenous connective tissue is a versatile tissue that plays essential roles in various body structures, providing strength, support, and protection..

[Audio] Connective tissue Hyaline Cartilage Structure: Function Location Collagen fibers are small and evenly dispersed in the matrix Chondrocytes are found in spaces Allows growth of long bones Provides rigidity with some flexibility in trachea, bronchi, ribs and nose Growing long bones Cartilage rings of the respiratory system Costal cartilage of ribs Nasal cartilage ma·trix /ˈmātriks/ noun noun: matrix; plural noun: matrices; plural noun: matrixes 1. an environment or material in which something develops; a surrounding medium or structure. "free choices become the matrix of human life" Chondrocytes a cell which has secreted the matrix of cartilage and become embedded in it. Rigidity unable to bend or be forced out of shape; not flexible..

[Audio] Connective tissue Fibrocartilage Structure: Function Location Collagen fibers similar to those in hyaline cartilage Fibers are more numerous than in other cartilages and are arranged in thick bundles Somewhat flexible and capable of withstanding considerable pressure connects structures subjected to great pressure Inverted disks pubic symphysis and articular disks (Knee and temporomandibular (Jaw) joints) Function: Support and Strength: Provides support to structures under considerable pressure. Shock Absorption: Capable of withstanding and distributing compressive forces, making it ideal for areas subject to heavy loads..

[Audio] Connective tissue Elastic Cartilage Structure: Function Location Similar to hyaline cartilage, but matrix also contains elastic fibers Provides rigidity with even more flexible than hyaline cartilage because elastic fibers return to their original shape after being stretched External ears Epiglottis Auditory tubes Epiglottis a flap of cartilage at the root of the tongue, which is depressed during swallowing to cover the opening of the windpipe. (Base of tongue).

[Audio] Connective tissue Supporting Connective Tissue Structure: Function Location Hard Bony matrix Many osteocytes Provides great strength and support and protects internal organs such as brain Bone also provides attachment sites for muscles and ligaments All bones of the body Osteocytes a bone cell, formed when an osteoblast becomes embedded in the matrix it has secreted..

[Audio] Connective tissue Fluid Connective Tissue: Blood Structure: Function Location Formed elements Fluid matrix Transport oxygen, carbon dioxide, hormones, nutrients, waste products and other substances Protects body from infection Within the blood vessels White blood cells frequently leave the blood vessels and enter extracellular spaces Osteocytes a bone cell, formed when an osteoblast becomes embedded in the matrix it has secreted..

[Audio] Tissue Membranes Is a thin sheet or later of tissue that covers structure or lines a cavity (consist of epithelium) There are 4 membranes in the body 1 external and 3 internal External tissue membrane is the skin Smooth – example blood vessels A tissue membrane is a thin sheet or layer of tissue that serves to cover structures or line cavities within the body, primarily consisting of epithelial tissue. There are four main types of membranes in the body: one external and three internal. The external tissue membrane is the skin, which protects the body from external elements and helps regulate temperature. The three internal membranes include mucous membranes, which line body cavities that open to the exterior; serous membranes, which line closed body cavities and cover organs; and synovial membranes, which line joint cavities. Each type of membrane plays a vital role in protecting and supporting various functions within the body..

[Audio] Tissue Membranes Mucous Membrane Line cavities that open to the outside of the body such as: Digestive Respiratory Reproductive tracts Outside meaning within the cells there is space/ diffusion/ osmosis can take place or absorption.

[Audio] Serous Membrane Line cavities that do not open to exterior of the body such as: Pleural Pericardial Peritoneal Do not open meaning no diffusion, osmosis, or absorption Pleural Membrane: Lines the thoracic cavity and surrounds the lungs, facilitating smooth movement during breathing. Pericardial Membrane: Encases the heart, allowing it to move freely within the chest cavity while protecting it from friction. Peritoneal Membrane: Lines the abdominal cavity and covers the abdominal organs, providing support and reducing friction as the organs move. Serous membranes are essential for maintaining the proper function of internal organs by providing a lubricated surface that prevents damage and allows for movement..