By Theophilus Bhatti BSc (hons) MLT, MS (Micro & Immuno) Human Tissues By Theophilus Bhatti BSc (hons) MLT, MS (Micro & Immuno)

Tissue Biological tissue is a collection of interconnected cells that perform a similar function within an organism. Cells in a Tissue have common embryonic origin Morphological features Arrangement

Types of Tissues Although there are many types of cells in the human body, they are organized into four broad categories of tissues

Task: How these Ts. are formed?

Epithelial Tissue Epithelial cells cover or line all body surfaces, cavities and tubes. So, These are called covering epithelia. Epithelial cells form the functional units of secretory glands. So, These are called glandular epithelia.

Functions:  Protection of underlying tissues from radiation, desiccation, toxins, invasion by pathogens, and physical trauma. The regulation and exchange of chemicals Secretion of hormones Secretion of sweat, mucus, enzymes etc Sensation Absorption Filtration

Classification of Epithelia Based on thickness simple stratified Pseudostratified Based on shape squamous cuboidal columnar

Simple Squamous Epithelium Description: Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia. Function: Passive transport of gases and fluids. Location: Alveoli of lungs, lining body cavities (mesothelium), lining blood vessels (endothelium)

Simple Cuboidal Epithelia Description : Single layer of cubelike cells with large, spherical central nuclei. Function : Secretion and absorption. Location: Kidney tubules; ducts and secretory portions of small glands; ovary surface.

Simple Columnar Epithelia Description: Single layer of tall cells with round to oval nuclei. Types: (i)Ciliated columnar epithelia. (ii)Non-ciliated columnar epithelia. Function: Absorption; secretion of mucus, Enzymes and other substances. Location: Digestive tract, gall bladder etc.

Stratified Squamous Epithelia Description: Multilayered, surface cell are squamous, basal cells are cuboidal and divided constantly. Function: Protection. Location: Oral cavity, cervix, anal canal.

Stratified Cuboidal Epithelia Description: Generally two layers of cube-like cells. Function: Protection. Location: Large ducts of sweat glands, mammary glands and salivary glands.

Stratified Columnar Epithelia Description: Multilayered, superficial cells elongated and columnar. Function: Protection; secretion. Location: Rare in the body; small amount in the male urethra.

Pseudo Stratified Columnar Epithelia Description: Single cell layered, all cell attach to the basement membrane but not all reach the free surface. Nuclei at varying depth. Function: Secretion of mucus, propulsion of mucus by ciliary action. Location: Lines of trachea.

Transitional Epithelia Description: Characterized by domelike cells that are neither squamous nor columnar. The form of the cells changes. Function: Stretching and protection. Location: Bladder and part of urethra.

Connective Tissue As the name implies, connective tissue serves a "connecting" function. Unlike epithelial tissue which has cells that are closely packed together, connective tissue typically has cells scattered throughout an extracellular matrix of fibrous proteins and glycoproteins attached to a basement membrane. Most abundant & widely distributed tissue

Functions: Connects, binds and supports structures, Tendons, ligaments, etc. Protects & cushions organs and tissues, Insulates (fat) and Transports substances (blood). Storing reserve fuel

Types: Loose Connective Tissue Dense Connective Tissue Adipose Blood Cartilage Bone

Loose Connective Tissue  Description: Loose, most common type Function: holds organs in place and attaches epithelial tissue to other underlying tissues. Location: under skin, most epithelia

Loose Connective Tissue There are three main types: Collagenous fibers are made of collagen and consist of bundles of fibrils that are coils of collagen molecules. Elastic Fibers are made of the protein elastin and are stretchable. Reticular Fibers join connective tissues to other tissues.

Dense Connective Tissue Description: composed of large amounts of closely packed collagenous fibers. Function: help attach muscles to bones and link bones together at joints i.e. support, elasticity Location: Tendons, ligaments, skin, kidney capsule

Adipose Description: form of loose connective tissue that stores fat. Function: lines organs and body cavities to protect organs, insulate the body,  produces endocrine hormones. Location: Under Skin, around kidney, heart

Blood Description: fluid connective tissue, the matrix consists of the plasma and red blood cells, white blood cells & platelets Function: transport gases, nutrition; removal of waste; immunity

Cartilage Description: a form of fibrous connective tissue composed of closely packed collagenous fibers Function: flexible support, cushion between the bones of joints Location: nose, trachea,  ears, joints

Bone Description:  mineralized connective tissue that contains collagen and calcium phosphate, a mineral crystal Function: skeleton, support, movement

Muscle Tissues Muscle tissue is made of "excitable" cells that are capable of contraction. Associated with the bones of the skeleton, the heart and in the walls of the hollow organs of the body.

Muscle Tissue Functions: Movement Locomotion Maintains posture Produces heat Facial expressions Pumps blood Peristalsis Types Cardiac Muscles Skeletal Muscles Smooth Muscles

Cardiac Muscle Description: branched, striated muscle, Cells are joined to one another by intercalated discs Location: wall of heart Function: pumping of heart through electric impulses

Skeletal Muscles Description: not branced, long, striated cells with multiple nuclei, carry Blood vessels and nerves Location: attached to bones Function: Contraction (voluntary movement) Locomotion Head and neck movement Body posture

Smooth(Visceral) Muscles Description: long, spindle shaped single nucleated cells Location:  blood vessels, the bladder, digestive tract, hollow organs. Function: involuntary contraction Rhythmic  movement Propulsion

Nervous Tissues Description:  Groups of organized cells in the nervous system Function: controls the body’s movements, sends and carries signals to and from the different parts of the body, and has a role in controlling bodily functions  location: Nervous system (brain, spinal cord, and nerves)

Hope you are not nervous!