Tissue

• Tissue refers to groups of similar cells working together to perform specific functions, includes connective, epithelial, muscle, nervous
• Biological tissue is a group of cells in an organism that perform similar or related function to improve efficiency of operation by sharing the task among various specialised cells
• The study of tissue is called histology
• Muscle Tissue: mostly formed by the mesoderm and consisting of highly specialised cells called fibres. Their main feature is voluntary and involuntary movement through contraction using contractile proteins like actin and myosin
• Muscle tissues are highly adaptive and heavily vascularised to meet large energy requirements. They are highly vascularised as they require high energy consumption and are in constant use
• Muscle cells create ATP through cellular respiration, increasing the amount of glucose and oxygen and resulting in more energy production
• Muscle Tissue Functions: movement, motion, posture, stability, reinforcement, thermoregulation
• Functional Characteristics of Muscle Tissue: excitability, contractibility, extensibility, elasticity
• Muscle Tissue Types: cardiac muscle, skeletal muscle, smooth muscle
• Cardiac Muscle: cylindrical, branching cells, intercalated discs
• Skeletal Muscle: long, large, multiple peripheral nuclei
• Smooth Muscle: no striations, spindle-shaped, single central nucleus
• Epithelial Tissue: single or layered sheets of cells originating from all three germ layers that are developed line internal and external surfaces with classification determined by number of layers and the morphology of the surface cells
• Epithelial Tissue Functions: protection, absorption, excretion, secretion, filtration, sensory reception
• Epithelial tissues are polarised and rest on a basement membrane with one free unattached surface called the apical layer and one attached surface called the basal layer. The layers are held together by a glue-like intercellular substance
• Epithelial Tissue Characteristics: supported by connective tissue, avascular, polarity, regeneration
• Sheets of epithelial tissue are held together by specialised junctions
• Epithelial tissues are arranged in sheets for tissue integrity, barrier function, selective permeability, communication and physiological processes. They have one of the fastest rates of cell death and multiple layers ensure cell death does not create gaps or vulnerabilities in their protection of organs
• Specialised Features of Epithelial Tissues: cilia, goblet cells, villi, microvilli, keratin
• Cilia (or cilium singular) are hair-like appendages attached to the apical surface to produce movement and provide a sensory structure
• Goblet cells in epithelial tissues produce mucus to protect and lubricate the surface of organs
• Villi (or villus singular) are finger-like projections on the epithelial layer of some organs designed to increase surface area for faster and more efficient absorption. Their smaller counterparts are microvilli
• Epithelial Tissues are identified by their arrangements and shapes. They can be arranged as simple (single layer), stratified (multiple layers), pseudo stratified (single layer that appears to be multiple), or transitional (moving from one shape to another). Shapes include squamous, cuboidal and columnar
• Connective Tissue: developed from the mesoderm and consisting of variations of collagen, elastic and reticular fibres. Composed of extracellular matrix including ground substance, cells, and fibres. The most abundant and widely distributed tissue type found in the human body
• Connective Tissue Functions: connection, binding, protection, insulation, storage, transportation
• Epithelial Tissue Characteristics: most are vascular, made up of many specialised cell types, made up of cellular matrix including a large amount of non-living material
• Connective tissue are made up of mature and immature cells. Mature cells end in -cyte; e.g. fibrocyte, chondrocyte, osteocyte. Immature cells end in -blast; e.g. fibroblast, chondroblast, osteoblast and are not yet fully specialised
• Specialised Connective Tissue: adipose (energy storage), cartilage, bone (osseous tissue), blood, lymphatic tissue
• There are five types of connective tissue found in the human body
• Loose Connective Tissue: areolar, adipose, reticular
• Dense Connective Tissue: dense regular, dense irregular, elastic
• Cartilage: hyaline, elastic, fibrocartilage
• Bone is a form of Connective Tissue
• Blood is a form of Connective Tissue
• Connective tissue is the most abundant tissue and has many subclasses with their own unique structure and diverse function. Connective tissue is the most versatile of the four main tissues and plays essential roles in maintaining structure, function and intensity of the organism