Human Body, What is Animal Cell, Functions of the cells of the human body, Cells in Human Body, Basic Tissue in the Human Body, Human Body Organization, Long Bone (Cartilage) Development, Bone Human Body.
Living organisms have cells and tissues. They are both structurally present in all organisms and both have equal importance. Cells are an important part of tissues, without cells there is no problem and cells form a variety of tissues in all multicellular organisms.
There is mainly one cell present in every living organism. Let us learn the difference between cell and tissue. Cells are found in every living organism. It is present in every living being. No organism exists on planet earth without cell.
It is known as the smallest structural and functional unit of life. Thus, cells are known as the fundamental unit of life. These minute cells are responsible for everything that happens in the body. Living organisms are further classified into unicellular and multicellular organisms.
Definition Cells and Tissues :
A cell is the smallest functional unit of living material and surrounded by cell membrane. The cells act like body building bricks. There are different types of cells which form different tissues.
A Typical Animal Cell Organ and Function :
- Plasma membrane – protection of inner parts, transport across membrane, hormone and chemical receptors and antigenic properties.
- Nucleus – control cell activities and hereditary characters
- Fat droplet – energy source
- Golgi body – protein synthesized in a cell are concentrated here for secretion.
- Lysosome – They are formed by Golgi body. They contain enzymes which help in breaking down of cell organelles and large molecules like DNA, RNA, carbohydrates and proteins.
- Mitochondria – They act as power house of a cell. They are involved in aerobic respiration and synthesis of ATP.
- Centro some (Centrioles) – They are involved in cell division.
- Endoplasmic reticulum – They are involved in proteins, lipids and steroid hormonessynthesis.
- Ribosomes – They synthesise proteins from amino acids.
- Vacuole – They collect waste products in a cell
- Protoplasm – It is viscid and translucent colloid material containing water. It includes cytoplasm and nucleus.
Functions of the Cells of the Human Body :
- Protection – Blood Cells
- Absorption – Cells in the GIT
- Secretory – Cells in glands
- Sensation – Skin, nerve cells
- Reproduction and growth – Germ cells (sperm, ovum)
Cells in Human Body :
- Blood cells – They are present in blood circulatory system and help in oxygen carrying, Human body defense and blood clotting.
- Muscle cells – They are present in skeletal, visceral organs and heart. They help in movements.
- Epithelial cells – They are present in skin, mucous membrane and glands. They give protection to inner organs and glands secrete different hormones and body fluids.
- Endothelial cells – They are present in hollow organs like intestines, lungs, heart, uterus and blood vessels. They form the inner lining of these organs.
- Nerve cells – They are present in nervous system and sense organs. They carry sensations to brain and carry out different body movements.
- Bone cells – They are present in bones. They form body skeleton and provide attachment for muscles. They protect vital organs like brain, heart, lungs, intestines, liver and store calcium.
- Cartilage cells – They are elastic in nature and present at the end of long bones, joints, trachea, bronchi, nose and ear lobes.
- Fat cells – They contain fat and they are distributed allover the body. They act as cushion and source of energy reservoir.
- Connective cells – They are present all over the body. They connect different body parts together.
- Special cells (Rods and cones and other cells) – They are present in sense organs like eyes, ears, nose and tongue.
- Germ cells – They are produced by testes and ovaries. The two germ cells sperm and ovum unite and form embryo (zygote) which form different body cells, tissues and organs.
Basic Tissue in the Human Body :
- Epithelium – skin, glands, mucous membranes elastic
- Connective – fat, blood collagen fibers
- Muscular – muscles in different organs
- Neuro-brain and nerve fibers
- Sclerous tissue – bones and cartilage
Description of Body Tissues :
Epithelial Tissue – They are present in organs that cover the surfaces of the body e.g. skin. These tissues are also present in hollow organs such as the digestive system, heart, blood vessels and organs of the urinary system.
Types of Epithelial Tissues :
simple epithelial tissue – squamous (pavement, single layer of cells), Columnar (cuboidal cells in thyroid), ciliated, goblet cells and cuboidal.
Compound epithelial tissue (multiple layers of cells) – (1) stratified squamous (skin)
(2) transitional epithelium (urinary bladder)
Membrane – Epithelial tissue along with connective tissue form a functional unit in the body called a membrane that is moistened and lubricated with fluid, called a serous membrane. pleura, pericardium, peritoneum.
Mucous membrane – It is formed by epithelial cells that line the hollow organs. Goblet cells secrete a sticky substance called mucus that lubricates the surface and keeps it moist. Synovial membrane lines the joint cavity.
Function of Epithelial Tissue : Human Body
Protection – The skin protects the internal organs from heat and cold and acts as a dressing. Secretions by glands like mucus, digestive juices, sputum, sweat, hormones etc. Glands are secretory organs made up of epithelial cells.
Organs such as the liver, pancreas, hormone secreting glands (endocrine) mammary glands, glands in the digestive system, sweat sebaceous and salivary glands (exocrine) are all composed of epithelial cells.
Types of Glands : Human Body
Exocrine – with tubules (ducts) that carry secretions to the surface of the body or to other organs. These include the liver, pancreas and sweating, sebaceous, salivary mammary glands.
Endocrine – they occur without tubules. Their secretions are directly absorbed into the blood. Hormones secreted by endocrine glands include the pituitary, thyroid, parathyroid, thymus, adrenals, testes, and ovaries.
Connective Tissues : Human Body
Connective tissue helps to connect organs and parts of the body together. They provide the outline of the body. There are several types of connective tissue.
- Alveolar Tissue
- Reticulated (Replica)
- Mucoid Tissue
- Adipose Tissue
- Elastic Tissue
- Fibrous Tissue
Alveolar Tissue – These are loosely woven tissues that are present throughout the body. They are placed under the skin and mucous membranes. Alveolar tissues form a sheath called fascia. binds and supports the fascia muscles, nerves, blood vessels and other organs.
Alveolar tissue is composed of matrix (inter-cellular substance) in which connective tissue cells are present. These include fibrillates, fat cells, macrophages, leukocytes, mast cells. There are two types of fibers in alveolar tissues. White fibers which are fine collagen fibers, give tensile strength and elastic (yellow) Fibers give elasticity.
Reticulated (Replica) Lymphoid or Adenoid Tissue – They are similar to alveolar tissue. They contain a large number of lymphocytes. they are held together by reticulated fibers.
Mucoid Tissue – These are present in the umbilical cord and vitreous humor of the eye.
Adipose (adipose) tissue – These tissues are present in almost every body part and organ. There are droplets of fat in the cell. Adipose tissue supports the body’s organs and acts as insulation against heat and cold. It is also a source of heat and energy during metabolism.
Elastic Tissues – These contain a large amount of elastic fibers. They are present in blood vessel, respiratory tract, ligaments and vertebral column ligaments. They help keep the respiratory tract and blood vessels open to air and blood flow.
Fibrous Tissue – They are made of white fibers and give good strength. They are present between blood vessels, nerves, lymphatic vessels, the periosteum that covers the bones, the muscular sheath, the pericardium, and the fascia separating the sclera of the eye.
Muscular Tissue :
The muscle cells are cylindrical in shape, with both ends tapering like a spindle (needle). These cells contract and relax, allowing movement to take place. The muscle cells form a bundle that contracts and relaxes as a unit.
There are skeletal, striated or voluntary muscles. They are present in the skeleton (limbs, neck of the head, pelvis of the abdomen). They have alternating dark and light markings called striations. They contract and relax when stimulated by the nervous system (as per the will of the individual i.e. deltoid in shoulder and gluteus in hip) region. Involuntary muscles present in the digestive tract Respiratory tract Urinary system Blood vessels Iris in the skin of the eyes.
Sphincter muscles are present at the junction of the stomach, esophagus, anus, urethra, ileum, and cecum. They are circular muscles that close or open the hole when necessary.
Cardiac Muscles – they are present only in the heart. It is a striated-like voluntary muscle. The fibers are intertwined and colored red. They are not controlled by will. They are autonomous.
Muscle Tone : Human Body
Muscles contract when excited. Contractions vary from muscle to muscle. Voluntary muscles contract at a variable frequency. In voluntary muscles (non-striated) contractions are slow. The heart muscle in a normal person has a constant frequency of contractions. Muscles are never at rest. They are in a constant state of partial contraction.
Energy for muscle activity (contraction and relaxation) is provided by the breakdown of glycogen with the help of sufficient oxygen. Glycogen is simply converted to lactic acid if the oxygen supply is not sufficient. It happens In athletes and individuals whose heart maintains blood circulation at a normal rate.
Cartilage : Human Body
Also called gristle, it is a clear, bluish white substance that is firm in nature. It is less hard than bone. It is commonly found in joints, ends of bone cavities, tubular structures
(eg respiratory system, acetabulum cavity in hip joint, knee cartilage.
Cartilage does not have bone-like blood vessels but is covered by a membrane perichondrium by which they get nourishment. During development in the embryo, cartilage is transformed into various bones. Cartilage covers the ends of long bones.
Types of Cartilage :
- Hyaline Cartilage
- White fibrocartilage
- Yellow elastic cartilage
Hyaline Cartilage – Consists of collagen fibers embedded in a ground substance called matrix. It is firm, elastic and is found covering the ends of long bones, nose, larynx, trachea and bronchi. It is a temporary cartilage from which bone Make. The cells of hyaline cartilage are arranged in small clusters surrounded by a tough matrix.
White Fibrocartilage – This type of cartilage cells are arranged in bundles of fibers where great strength is required. This cartilage is seen in cavities such as the acetabulum in the hip joint and the glenoid cavity of the shoulder joint.
It is also seen as ‘C’ Rings of shaped (crescent) cartilage in the knee joint. It is also seen in the inter vertebral discs of the vertebral column (back bone) and symphysis pubis (joint of the two hip bones front). They are present in ligaments connecting two bones.
Yellow Elastic Cartilage – consists of many yellow elastic fibers. They are seen in the ear, epiglottis and auditory tubes. When pressure is applied they twist and change the shape of the organ. The organ takes its original shape when there is pressure Removed.
Bone : Human Body
Bone is a connective tissue. It is made up of osteocytes. Cells are surrounded by collagen fibers in which inorganic salts especially calcium and phosphate are deposited. Salts provide hardness and strength to the bones. Bones grow until the age of twenty and regenerate throughout life. Bones consist of 25% water, 50% calcium and 25% cellular elements in the solid part.
Types of Bone :
- Long – Femur Tibia etc.
- Short – Carpal
- Irregular – Vertebrae and Skull
- Flat – Sternum and Skull
- Sesamoid – patella (knee cap – it is present in the quadriceps – tendon of the thigh muscle)
Macroscopic Bone Structure :
A long bone has a shaft called the diaphysis and two ends (upper and lower) called the epiphysis or extremity. The shaft is made up of compact bone that is hard and dense. The cavity muscle of the shaft is called the medullary cavity. The cavity is fatty yellow bone marrow.
A long bone has red bone marrow at two ends (the epiphysis). The outer surface of the bone is covered with a tough membrane by the periosteum, which is fibrous and vascular (rich in blood supply). The blood supply to the long bone is through the alimentary artery which enters the bone through a hole called the nutrient foramina.
Microscopic Bone Structure :
Hard (brief) bone – it looks solid but is made up of a large number of canals that make up the Haversian system. It contains veins of blood and lymphatic vessels. Haversian canal is located in the middle and is surrounded by rings or plates of A bone called lamellae. These rings contain thin spaces called lacunae that contain tissue fluid and spider-shaped bone cells called osteocytes. This tissue fluid nourishes the bone cells.
Spongy bone – it looks like a honey comb. Some rings (plates) or lamellae are present around the Haversian canal. All the osteoblasts are connected to each other by thin tubules called canaliculi. The red bone marrow present in the vacuole provides nutrition to the osteocytes.
Cartilage and Bone cells :
- Osteocyte – It is a mature bone cell present in lacunae after the growth of bone is complete.They help in calcium movement between blood and bone.
- Osteoblasts – They are bone forming cells. They are present in periosteum, centre of bone ossification, end of diaphysesand close to epiphyseal cartilage site.
- Osteoclasts – Their function is boneresorption which gives shape and size to the bone.They help in bone formation (size and shape) during growth and healing.
- Chondroblast – Cartilage forming cells. They develop from fibrous tissue cells.
- Chondrocyte – Cartilage cell in mature cartilage.
- Osteogenic cells – The cells which form bones are called osteogesiccells
Cell Mutation :
It is a condition in which changes occur in the genetic material (DNA) in the nucleus. Conditions are X-ray chemicals, radiation, ultraviolet rays etc. The mutation can kill the cell; Change its actions and characters. If there are genetic changes in the sperm and egg, then future generations are affected.
Cell Division : Human Body
Mitosis – This is the process in which body cell (somatic) divide into two and the number of chromosomes remain the same (46) in each daughter cell produced.
Meiosis – By this method the germ cells (sperm ovum) are produced, by this method the number of chromosomes in each sperm and ovum is halved (23).
Bone Development (Ossification) :
The flat bones develop from membranes. They are called membranous bones. Muco-polysaccharide matrix (osteoid) secreted by collagen fibers. 1. Calcification of Osteoid, 2. It gradually replaces cartilage and membranes. Long bones develop into cartilage. They are called cartilage bones.
Flat (Membranous) Bone Development :
The connective tissue membrane is rich in blood supply. The bones of the skull are flat and they develop from membranes. Osteogenesis begins at a certain center and bone cells membrane and multiply within a fragile bone has been made.
After some time a flat bone is formed which is made up of two hard layers and is covered with periosteum which is a hard membrane that covers the bone. The spongy bone lies between two layers of hard bone plates.
Long Bone (Cartilage) Development :
All long bones in the developing embryo first develop as a cartilage rod covered with perichondrium. A primary center of ossification develops in the middle of the cartilage called the diaphysis. This will become the shaft of a long bone.
Calcium is laid down in the matrix. Osteocytes (bone cells) develop under the periosteum. Perichondrium converts into periosteum. As the age increases, the size of the bones increases in length and thickness. During the process of development, a secondary center of ossification appears at each end. This is called epiphysis.
In the epiphysis the fracture extends in both directions towards the shaft (diaphysis) and the end (extremity) of the bone. The hormones that control bone growth are growth hormone (pituitary), testosterone (testes), estrogen (ovaries), calcitonin (thyroid).
Nervous Tissues :
Is made up of three types of matter. 1. White matter – Nerve fibers 2. Gray matter – Nerve cells 3. Neurological – Supporting cells hold together nerve cells and fibers. Each nerve cell with process is called neuron.The nerve cell has following characteristics
- Irritability – To start the impulse.
Conductivity – To transmit the impulse :
Neurons respond to stimuli such as touch, light, smell, sound, cold, hot and taste. Stimulation can be mechanical, electrical, chemical or mental. The stimulus will induce an impulse that travels through nerve fibers to the brain or target organ.
A nerve impulse will start from the dendrite to the cell, from the cell to the axon (nerve fiber). This impulse will pass through many cells before reaching the target organ.
Types of Impulses :
- Motor impulse – results in movement or locomotion (brain to organs).
- Sensory impulse – Results in sensations like touch pain or special sensations like taste, hearing vision etc. (From organs to brain)
Types of Nerve fibers :
- Motor (Efferent) Nerves – They carry impulses from Brain to spinal and peripheral organs. (motor pathway)
- Sensory (Efferent) – from peripheral organs to Brain.
- Mixed – They carry both motor and sensory impulses.
Fluid Connective tissue :
- Blood = blood cells + plasma
- Lymph = Tissue fluid + Lymphocytes
Tissue Regeneration :
- Labile cells – replication is continuously taking place in epithelium in skin, glands, spleen, blood, lymphoid, bone, neurons.
- Stable cells – liver, kidney, pancreas, fibroblasts, smooth muscle cells, osteoblasts and osteoclasts.
- Permanent cells – They are unable to regenerate- nerve cells skeletal and cardiac muscles.
Human Body Organization :
- Body parts
Central –
- Chest (Thorax)
- Abdomen
- Vertebral Column
- Pelvis
Peripheral –
- Upper Limbs
- Lower Limbs
Body Cavities :
- Cranial
- Chest
- Abdomen
- Pelvis
Basic Anatomical Terms :
Directional Terms and Their Meaning –
- Medial – The structure is nearer to midline of the body i.e. heart is medial to arm.
- Lateral – The part is away from midline i.e. arm is lateral to heart.
- Proximal – The part is near to the origin or attachment i.e. femur is proximal to tibia.
- Distal – The part is away from the origin or attachment i.e. ulna is distal to humerus.
- Anterior or Ventral – Part or organ of the body is close to front of the body i.e. clavicle is anterior to vertebrae.
- Posterior or Dorsal – Part or organ of the body is close to back of the body.
- Superior – Part or organ is close to head i.e. skull superior to sternum.
- Inferior – Part or organ is away from head i.e. Pelvis is inferior to skull
Questions for practice : Human Body
- Define anatomy.
- Write the scope of anatomy in MLT program.
- Define different anatomical terms.
- Draw diagrams of different cells and label them.
- What are the functions of each cell part?
- Name the different body tissues, draw and label them and write their function.
- Name the different glands and write their functions.
- Name the different cells and write their functions
- Draw and label different body cells
- Describe and draw different tissues.
- Write the function of each tissue.
- Name the different glands and write their function.
- Write the function of Bones.
- Draw the structure of a long bone.
- What is human in human body?
- What are the 4 major parts of human body?
- What are the 7 systems of the human body?
- Are there 78 organs in the human body?
- What are the important organs of the human body?
- What are the different systems of our body?
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