Cells, Tissues, and Major Organs Systems Essay

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Introduction

A cell is the basic functional, structural, and biological unit of a living organism (Latham 2009). The element can reproduce independently. As such, cells are regarded as the building blocks of life. Cells are made up of cytoplasm, which is held within a membrane. In addition, they contain numerous bio-molecules.

In this paper, the author will analyze animal cells, tissues, and primary organ systems. The report will cover the structure and functions of animal cells and organelles. It will also address the structure and functions of tissues and main organs of the body.

The Structure and Function of Animal Cells and Organelles

The Main Structural Features of an Animal Cell

Animal cells are eukaryotic. Thibodeau and Patton (2003) note that their structure varies based on their type and function in the body. However, a typical animal cell has various distinct structural features.

Table 1: The main structural features of an animal cell.

Main Structural Features of an animal cell
Presence of a plasma membraneAn animal cell is enclosed by a plasma membrane. The cytoplasmic membrane is a biological feature separating the intracellular components from the outside environment (Martini & Timmons 2006).
Size and shapeAnimal cells are of different sizes and irregular shapes. However, most of them range between 1 and 100 micrometers (Marieb & Wilhelm 2014). Due to their minute dimension, they are only visible through a microscope.
Lack of a cell wallA cell wall is a tough rigid layer made of polysaccharides. It is found outside the plasma membrane of plants, bacteria, and fungi cells. The lack of a wall in animal cells is associated with their irregular shapes.

The Functions of the Main Parts of an Animal Cell

An animal cell is made up of a membrane-bound nucleus. Tortora and Nielsen (2012) note that the cell contains a number of cellular organelles. The numerous parts carry out distinct functions. The main components include the cell membrane and the extracellular matrix. Others are the nucleus, golgi apparatus, mitochondria, and endoplasmic reticulum. It also contains ribosome, lysosome, peroxisome, and cytoskeleton.

Table 2: The functions of the major parts of an animal cell.

StructureMolecular CompositionFunction
Cell membrane (plasma membrane)They comprise of a number of biological molecules, namely lipids and proteins. The ratio of proteins and lipids layers is 50:50.The membrane contains unambiguous systems, pumps, and channels. They are used to exchange nutrients and other vital materials between the cell and the environment (Marieb & Hoehn 2010). In addition, the membrane houses essential enzymes, which support the normal functioning of the cell.
MitochondriaThey are organelles surrounded by two layers, which are the inner and the outer membranes. The two have different protein and lipid compositions. The mitochondria are spherical or rod shaped. In terms of size, they are of equal dimension to bacteria. Animal cells contain hundreds of mitochondria. Light (2004) notes that the components occupy about one-fifth of the entire cell volume.The mitochondria act as the power house of eukaryotic cells. They oxidize fats, carbohydrates, and amino acids to CO2 and H2O.
NucleusIt is enclosed by a porous crust referred to as a nuclear membrane. Its DNA contains basic proteins, which form chromatin fibres. In addition, the nucleus houses numerous RNAs, which form the ribosome.The nucleus controls the functioning and chemical processes of the animal cell. Latham (2009) notes that it is the repository of genetic information found in DNA.
Extracellular matrixAnimal cells are characterised by layers of complex proteins, carbohydrates, and lipids (Fried & Hademenos 2013).Each cell has a distinct coating. The primary function of the extracellular matrix is to enable cell-to-cell communication and recognition.
Golgi apparatusThe apparatus are a set of flattened stacks of membrane-bound sacs. The component contains numerous minute vesicles.The apparatus carry out the packaging work. They modify rough endoplasmic reticulum molecules by dividing them into lesser entities.
Endoplasmic reticulumThere are two types of ER. They include rough and smooth ER. They are flattened tubes, sheets, and sacs that stretch to the cell cytoplasm.The ER acts as the transport system of an animal cell. Thibodeau and Patton (2003) note that ER carries molecules to different destinations within the cell.
RibosomeThey are attached to the rough ER.The primary function of ribosome is protein synthesis.
LysosomesLysososmes are membrane-bound. They have a diameter of between 0.2 and 0.5 µm. According to Clancy (2011), lysosomes contain hydrolytic enzymes, which help in cell detoxification.Lysosomes act as the digestive systems of a cell. They contain a number of enzymes that help in the digestion of carbohydrates, lipids, and proteins.
CytoskeletonIt comprises of numerous protein filaments. The fibres develop the structure function of the cytoskeleton.The primary function of the cytoskeleton is to determine the shape of the cell and allow mobility.
PeroxisomesThey are bound by a single membrane. In addition, they have similar dimensions to lysosomes. They are formed through the binding process in the smooth ER.The primary function of Peroxisomes is to oxidise different nutrients, such as amino acids (Fox 2011).

The Structure and Sub-Types of Body Tissues

A tissue is a group of cells that have the same functions and shapes. Light (2004) notes there are four primary forms of tissues in humans. They include connective, nervous, epithelial, and muscular tissues. Each of these has a number of sub-tissues.

Connective Tissue

Overview

They are fibrous in nature. They comprise of cells separated by extracellular matrix. Connective tissues are made up of three primary components. The constituents are fibres, cells, and ground substances. However, Clancy (2011) observes that blood and lymph do not contain the three major elements.

The drawing below is a depiction of a connective tissue:

Connective tissue.
Figure 1: Connective tissue.

Subtypes of connective tissues

There are diverse sub-types of connective tissues with different structures. They include blood, bone, fibrous connective tissue, adipose tissue, and cartilage.

Adipose tissue is one of the most important sub-tissues. It is made up of 80% fat and adipocytes (Martini & Timmons 2006). It is regarded as a primary endocrine organ. The reason is that it secretes several hormones. Such hormones include estrogen, cytokine, leptin, and resistin. The figure below is an illustration of adipose tissue:

Adipose tissue.
Figure 2: Adipose tissue.

Cartilage

The subtype is made up of specialised cells referred to as chondroblasts. According to Marieb and Hoehn (2010), the cells produce copious amounts of ground substance and extracellular matrix. The figure below is a depiction of this sub-tissue:

Cartilage.
Figure 3: Cartilage.

Blood

Blood is a special body fluid in animals. The subtype of connective tissue is made up of cells suspended in plasma. The figure below illustrates this connective tissue:

Blood.
Figure 4: Blood.

Epithelial Tissue

The tissue is formed by cells that cover the surfaces of different organs. Cells that make up the epithelial layer are joined by semi-permeable and rigid intersections (Manolis 2009).

Subtypes of epithelial tissue

There are numerous subtypes of epithelial tissues. They include simple squamous, cuboidal, columnar, stratified squamous, and stratified cuboidal tissues. Each subtype has a unique structure.

Simple squamous

They are thin, flat, and single layers tightly fit together. In addition, they are permeable and susceptible to damage. The figure below shows a simple squamous:

Simple squamous.
Figure 5: Simple squamous.

Simple Cuboidal

Fox (2011) notes that the epithelial subtypes are single layered and cube-shaped.

Simple cuboidal.
Figure 6: Simple cuboidal.

Simple columnar

The epithelial subtype is single layered, elongated, and nucleic (Mai 2012). In addition, it is comprised of microvillus and goblet cells.

Simple columnar.
Figure 7: Simple columnar.

Nervous Tissue

The nervous tissue is composed of specialised cells that receive stimuli and conduct pulses to and from all parts of the body. The cells making up the nervous tissues are long and string shaped.

Subtypes of nervous tissues

Neurons

They exist in different forms and sizes. According to Mai (2012), neurons are characterised anatomically. The structural classifications include unipolar, bipolar, multipolar, and anaxonic.

A neuron.
Figure 8: A neuron.

Glial cells

According to Latham (2009), these cells comprise of ample support systems. They ensure proper functioning of the nervous system.

A glial cell.
Figure 9: A glial cell.

Muscle Tissue

A muscle tissue is made of excitable cells with contraction abilities. In addition, it contains lots of microfilaments, which consist of contractile proteins. The muscle tissue is the most common of all the four subtypes.

A muscle tissue.
Figure 10: A muscle tissue.

Subtypes of muscle tissues

Cardiac muscle

It is made up of cardiomyocyte cells, which contain three nuclei. In addition, it has numerous cross-striations. The striations are formed by revolving fragments of protein fibres (Mohrman & Heller 2010).

A cardiac muscle.
Figure 11: A cardiac muscle.

Smooth muscle

Smooth muscles have a fusiform shape and a tensing and relaxing capability. In a relaxed state, the tissue is often spindle-shaped.

A smooth muscle.
Figure 12: A smooth muscle.

Skeletal muscle

The muscles are made up of myocytes (Thibodeau & Patton 2003). They contain collagen fibres referred to as tendons. The fibres help them append to the bones.

A skeletal muscle.
Figure 13: A skeletal muscle.

The Location and Function of the Four Main Tissues and Sub-Tissues 1.1. Connective Tissue

The tissues are located between other tissues found in the animal body (Martini & Timmons 2006). They cover most animal parts. The functions of connective tissues include providing a medium of diffusion for nutrients and oxygen into the cells from the capillaries. In addition, they prevent the overstretching and tearing of organisms.

Connective tissue subtypes: Location and functions

Adipose tissue

The tissue is located in the liver and other muscles (Manolis 2009). Its primary purpose is to store energy in form of lipids. In addition, it stifles and insulates the body.

Cartilage tissue

The tissue is found in various parts of the animal. The parts include ribcage, nose, ear, bronchial tubes, knee, and between the bones. Other areas are elbow and intervertebral discs. The main function of cartilage is to connect organs.

Blood

It is found in the entire body. Its primary purpose is to transport nutrients and oxygen to the cells (Clancy 2011). In addition, the component is responsible for carrying away metabolic waste.

Epithelial Tissue

The tissue is found in the skin. Its primary function is to cover surfaces found inside the organism and body cavities.

Epithelial tissue: Location and function of subtypes

Simple squamous

They are located in the walls of capillaries, air sacs, and blood vessels. Their primary function is filtration and diffusion (Marieb & Wilhelm 2014).

Simple Cuboidal

They are located in the kidney tubules, liver, salivary glands, and pancreas. Their main function is secretion and absorption.

Simple columnar

They are found in the lining of the digestive tract and uterus (Thibodeau & Patton 2003). Their primary function is the secretion of such substances like mucus and enzymes.

Nerve Tissues

The tissues are located in the brain, heart, lungs, and kidneys. Their primary functions include controlling, supporting, and protecting neurons.

Nerve tissues: Location and function of subtypes

Neurons

They are found in the brain and the spinal cord. The primary function of neurons is the transmission of information (Carter & Aldridge 2009).

Glial cells

They are located in the brain and the spinal cord. Their main function is to insulate neurons.

Muscle Tissues

The tissues are located in the heart, bones, and hollow organs. Their main function is to facilitate the movement of the organ walls and the skeleton.

Location and function of muscle sub-tissues

Cardiac muscles

They are located in the heart. Their primary function is to synchronize the heartbeat.

Skeletal muscles

They are found in the bones. They are intended to move bones (Manolis 2009).

Smooth muscles

They are located in the arteries, digestive tract, and bladder. Their primary function is to facilitate movement in hollow organs.

Location, Size, and Function of the Main Organs of the Body

Table 3: Main organs of the body.

OrganLocationSizeFunction
BrainHead, protected by the skullIn humans, the brain of the average adult is 1130cm3 for females and 1260cm3 for males (Thibodeau & Patton 2003).Control the actions of the entire body.
LungsBoth sides of the chestSurface area ranges from 30-50 to 70-100 square meters (Martini & Timmons 2006).Enable oxygen get into the red blood cells. Help the human body get rid of CO2.
HeartMiddle section of the mediastinum in the chest.315g for males and 265g for femalesPump blood and oxygen to all parts of the body (Mohrman & Heller 2010).
LiverUpper right compartment of the abdominal cavity7cm for females and 10.5cm for males (Tortora & Nielsen 2012).Production of bile and proteins for blood plasma.
PancreasBack of the abdomenAbout 6 inches longProduction of digestive juices and insulin.
StomachLeft side of the upper abdomen45-75 millimetres when relaxed for adults and 30 millimetres for newbornsStore and break down liquids and foods (Thibodeau & Patton 2003).
Small intestineBetween the stomach and the large intestineAbout 6 to 7 meters long (Fox 2011).Absorption of minerals and nutrients from food
Large intestineLower right abdomenAbout 1.5 meters longStorage of waste, absorption of vitamins, and reclaiming of water.

Three Major Organs with Reference to Tissue Types and Subtypes

Table 4: Three major organs.

OrganTissueTissue structureTissue subtypeSystem incorporating the organ
BrainNervousMade of nerve cells referred to as neurons (Light 2004).Neurons and glialsLimbic, cerebrum, and cerebellum
Small intestinesEpitheliumMade of cells packed in one or more layers.Simple, stratified, and transitionalDuodenum, ileum, and Ileocecal valve.
HeartMuscleMade of elongated cells (Mohrman & Heller 2010).Cardiac, skeletal, and smooth.Cardiovascular system

The table above shows three main organs with reference to their tissues, sub-tissues, and system.

References

Carter, R & Aldridge, S 2009, The human brain book, DK Pub., London.

Clancy, J 2011, The human body close-up, Firefly Books: Richmond Hill, Ontario.

Fox, S 2011, Human physiology, 12th edn, McGraw-Hill, New York.

Fried, G & Hademenos, G 2013, Biology, 4th edn, McGraw-Hill Education, New York.

Latham, D 2009, Cells, tissues, and organs, Raintree, Chicago, Illinois.

Light, D 2004, Cells, tissues, and skin, Chelsea House, Philadelphia.

Mai, J 2012, The human nervous system, 3rd edn, Elsevier Academic Press, Amsterdam.

Manolis, K 2009, The skeletal system, Bellwether Media, Minneapolis.

Marieb, E & Hoehn, K 2010, Human anatomy & physiology, 8th edn, Benjamin Cummings, San Francisco.

Marieb, E & Wilhelm, P 2014, Human anatomy, 7th edn, Pearson, Boston.

Martini, F & Timmons, M 2006, Human anatomy, 5th edn, Pearson/Benjamin Cummings, San Francisco.

Mohrman, D & Heller, L 2010, Cardiovascular physiology, 7th edn, McGraw-Hill Medical, New York.

Thibodeau, G & Patton, K 2003, Anatomy & physiology, 5th edn, Mosby, St. Louis.

Tortora, G & Nielsen, M 2012, Principles of human anatomy, 12th edn, John Wiley & Sons, Hoboken.

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