Module 4: Tissues

Connective tissue composed of

Cells Ground substance - matrix Protein fibres - matrix

Types of fibres embedded in the matrix between the cells of connective tissue

Collagen fibres Elastic fibres Reticular fibres

Perichondrium

Surrounds cartilage Dense irregular CT

Exocrine glands

Sweat, oil and digestive glands Secrete their products into ducts that empty at the surface of the covering and lining of the epithelium or directly onto free surface

Leukocytes

WBCs Phagocytosis, immunity, allergic reactions

Mast cells

Abundant alongside blood vessels and produce histamine

Matrix

Abundant with relatively few cells Tends to prevent tissue cells from touching one another Can be fluid, semifluid, gelatinous, fibrous, or calcified Usually secreted by connective tissue cells and adjacent cells and determines quality of tissues Most mature cells have a reduced capacity for cell division and matrix formation and are mostly involved in maintaining the matrix

Types of loose connective tissue

Areolar Adipose Reticular

Features of epithelial tissue

Arranged in sheets either in single or multiple layers Has an apical surface (free, exposed to body cavity), lateral surface, and basal surface attached to a base membrane Epithelia adhere firmly to nearby connective tissue through a thin extracellular layer called the basement membrane. Epithelia have a nerve supply and a high capacity for renewal Avascular, the exchange of materials between epithelium and adjacent connective tissue is by diffusion

Skeletal muscle tissue

Attached to bones, striated, voluntary

Nervous system

Composed of neurons and neuroglia

Collagen fibres

Composed of the protein collagen, are very tough and resistant to stretching, yet allow some flexibility in the tissue, are found in bone, cartilage, tendons, and ligaments

Elastic fibres

Composed of the protein elastin, provide strength and stretching capacity and are found in skin, blood vessels, and lungs

Lamella

Concentric rings of matrix that consist of mineral salts that give bone its hardness, and collagen fibres that give bone its strength

Neurons

Consist of a cell body and dendrites and axons Sensitive to stimuli, convert stimuli into nerve impulses, and conduct nerve impulses to other neurons, muscle fibres, or glands

Epithelial membrane

Consist of an epithelial layer and an underlying CT layer Mucous membranes Serous membranes Cutaneous membrane or skin

Epithelium

Consists mostly of packer cells with little extracellular material. Many cell junctions are present, providing secure attachments among cells

Cartilage

Consists of a dense network of collagen fibres (strength) and elastic fibres embedded in chondroitin sulfate (resilience) Chondrocytes occur within spaces called lacunae in the matrix Has no BVs or nerves (except periochondrium) Growth is through interstitial growth and appositional growth

Reticular connective tissue

Consists of a fine interlacing of reticular fibres and reticular cells Helps to bind together the cells of smooth muscle Forms the stroma of certain organs: liver, spleen...

Loose connective tissue

Consists of all three types of fibres, several types of cells, and a semi-fluid ground substance Areolar Adipose Reticular

Dense regular connective tissue

Consists of bundles of collage fibres in a regular orderly and parallel arrangement that confers great strength Provides strong attachments Forms tendons, ligaments and aponeuroses

Reticular fibres

Consists of collagen and glycoprotein, provide support in the walls of the blood vessels and form a strong, supporting network around fat cells, nerve fibres, and skeletal and smooth muscle fibres

Elastic connective tissue

Consists of elastic fibres and fibroblasts Quite strong and can recoil back to its original shape after being stretched Allows stretching of organs Lung tissue and elastic arteries

Areolar connective tissue

Consists of fibres arranged randomly and several kinds of cells embedded in a semifluid ground substance Mostly fibroblasts Strength, elasticity, support Combined with adipose tissue forms subcutaneous layer In and around nearly every body structure

Stratified squamous

Consists of several layers of cells in which the top layer of cells is flat and deeper layers of cells vary in shape from cuboidal to columnar Keratinized or nonkeratinized Keratin is protein resistant to friction with a capacity to repel bacteria, forms tough layer Nonkeratinized remains moist

Stratified columnar

Consists of several layers of cells of which only the top layer is columnar, somewhat rare Protection, secretion Urethra, excretory glands, anal mucous membrane, eye

Transitional

Consists of several layers of cells; appearance is variable Capable of stretching so allows distention of organ Urinary bladder, ureters, urethra

Ciliated simple columnar

Contain cells with cilia, some goblet cells Mucus forms film, cilia move particles Upper respiratory tract, fallopian tubes, uterus, nasal, SC

Nonciliated simple columnar

Contain microvilli to increase SA and goblet cells which secrete mucus Secretion and absorption GI tract, gland ducts, gallbladder

Elastic cartilage

Contains a threadlike network of elastic fibres within the matrix Perichondrium Provides strength and elasticity, maintains shape of organs Part of ear

Fibrocartilage

Contains bundles of collagen fibres in its matrix Does not have perichondrium Combined strength and rigidity = strongest Support and joining structures together Intervertebral disks

Dense irregular connective tissue

Contains collagen fibres that are irregularly arranged Usually occurs in sheets Found in parts of the body where tensions are exerted in various directions Provide tensile strength Dermis of skin, heart valves...

Central (Haversian) canal

Contains the BVs and nerves Spongy bone has trabeculae rather than osteons

Dense connective tissue

Contains thicker, denser and more numerous fibres that LCT but considerably fewer cells

Types of epithelia

Covering and lining Glandular

Epithelial tissue

Covers body surfaces; lines hollow organs, body cavities, and ducts; and forms glands. Provides external protection for underlying tissue

Macrophages or histocytes

Develop from monocytes and are phagocytic

Endocrine glands

Ductless; secretory products enter the ECF and diffuse into blood

Types of tissue

Epithelial - protection Connective - support Muscle - movement Nervous - transmit impulses

Formed elements

Erythrocytes Leukocytes Thrombocytes

Muscle tissue consists of

Fibres that are modified for contraction, and provide motion, maintenance of posture, and heat production

Types of cells found in connective tissue

Fibroblasts Macrophages or histocytes Mast cells Adipocytes or fat cells

Membranes

Flat sheets of pliable tissue that cover or line part of the body

Cardiac muscle tissue

Forms wall of heart, striated, usually involuntary

Smooth (visceral) muscle tissue

Found in walls of hollow internal structures (BVs and viscera), is nonstriated, usually involuntary Provides motion

Tissue

Group of similar cells that usually have a similar embryological origin and are specialized for a particular function

Pseudostratified columnar

Has only one layer but gives appearance of many All cells are attached to basement membrane but some do not reach apical surface In ciliated, cells that reach surface secrete mucus (goblet cells) or bear cilia that sweep away mucus and trapped foreign particles Nonciliated have no cilia or goblet cells, function in absorption and protection Upper respiratory tract (ciliated), gland ducts, epididymis, male urethra (nonciliated)

Types of cartilage

Hyaline Fibrocartilage Elastic

Substances in ground substance

Hyaluronic acid, chondroitin sulfate, dermatan sulfate, and keratan sulfate

Epithelial layer of a mucous membrane

Important aspect of body's defence mechanisms, acting as a barrier to pathogens and a trapping surface for particles

Nervous tissue

Initiates and transmits action potentials that help coordinate body activities, monitors the external environment, and contributes to homeostasis

Lymph

Interstitial fluid flowing in the lymph vessels

Connective tissue characteristics

Is the most abundant and widely distributed tissue in the body Do not occur on free surfaces Highly vascular (except for cartilage and tendons) Nerve supply (except cartilage)

Connective tissue layer of a mucous membrane

Lamina propria

Mucous membrane

Line cavities that open to the exterior, such as the GI tract

Synovial membrane

Line joints, bursae, and tendon sheaths and contain only connective tissue Do not contain epithelium Secrete lubricating synovial fluid

Endothelium

Lines heart, blood vessels, and lymphatic vessels

Mesothelium

Lines the thoracic and abdominopelvic cavities, and covers the organs with them

Types of connective tissue

Loose connective tissue Dense connective tissue Cartilage Bone Liquid (blood and lymph)

Adipose connective tissue

Loose connective tissue consisting of adipocytes, which are specialized for storing triglycerides Reduces heat loss through the skin, serves as E reserve, supports protects and generates heat to help maintain proper body T in newborns Wherever areolar CT is located, around heart and kidneys

Basement membrane

Made up of a cellular layer of collagen and glycoproteins called the basal lamina; often, it is underlain with a layer of reticular fibres and glycoproteins called the reticular lamina

Canaliculi

Minute canals containing the processes of osteocytes which provide routes for nutrient and waste transport

Stratified

More durable and protective tissue

Hyaline cartilage

Most abundant but weakest Fine collagen fibres embedded in gel-type matrix Provides flexibility and support At joints reduces friction and absorbs shock

Blood

Vascular tissue Consists of a liquid matrix called plasma, and formed elements

Bone

Osseous tissue Consists of a matrix containing mineral salts and collagenous fibres and cells called osteocytes Classified as either compact or spongy depending on how matrix and cells are organized Supports, protects, helps to provide movement, stores minerals, and houses blood forming tissue

Basic unit of compact bone

Osteon/Haversian system 1. Lamella 2. Lacunae 3. Canaliculi 4. Central (Haversian canal)

Thrombocytes

Platelets Blood clotting

Tissue repair

Process of replacing dead or damaged cells Can only occur when inflammation is complete

Neuroglia

Protect and support neurons and are often the sites of tumours of the NS

Functions of epithelia

Protection, filtration, lubrication, secretion, digestion, absorption, transportation, excretion, sensory reception, and reproduction

Connective tissue

Protects and supports the body and its organs, binds organs together, stores E reserves as fat, and provide immunity

Erythrocytes

RBCs Transport respiratory gases

Stratified cuboidal

Rare tissue that consists of two or more layers of cube shaped cells Protective Sweat gland ducts, esophageal glands, male urethra

Muscle tissue

Responsible for movement and generation of F

Fibroblasts

Secrete fibres and matrix

Serous membrane

Serosa Lines a body cavity that does not open directly to the exterior and covers organs that lie within the cavity Pleura (thoracic cavity), pericardium (heart cavity), peritoneum (abdominal cavity) Epithelial layer secretes a lubricating serous fluid that reduces friction between organs and the walls of the cavities Parietal layer attaches to wall, visceral to organs

Classification of epithelia

Simple Stratified Pseudostratified Squamous Cuboidal Columnar Transitional

Simple cuboidal

Simple layer of cube shaped cells Secretion and absorption Kidneys, glands, ovary, eye

Gland

Single cell or mass of epithelial cells adapted for secretion

Simple squamous

Single layer of flat, scalelike cells Diffusion and filtration Lungs, kidneys, heart, blood vessels, lymphatic vessels Mesothelium and endothelium

Simple columnar

Single layer of rectangular cells 1. Nonciliated simple columnar epithelium 2. Ciliated simple columnar epithelium

Lacunae

Small spaces between the lamellae that contain mature bone cells called osteocytes

Adipocytes or fat cells

Store E in the form of fat

Ground substance aids in...

passage of nutrients from the BVs of connective tissue to adjacent cells and tissues Found in subcutaneous layer