Anatomy and Physiology: Structure and Function

• The human body is made of billions of smaller structures of four major kinds
• Cell -> Tissue -> Organ -> System

Definition of Human Anatomy and Physiology (HAP)

• It refers to the study of the structure of individual body parts and how they function
• The study of the human body involves two major principles: Anatomy and Physiology

Anatomy

• It is the branch of biological science dealing with the study of the structure of different body parts
• Subdivisions include:
• Cell Biology / Cytology: Study of cellular structure
• Histology: Study of tissue structure
• Gross Anatomy: Study of structures visible to the naked eye
• Microscopic Anatomy: Study of very small structures
• Systemic Anatomy: Study of specific body systems
• Radiographic Anatomy: Study of structures with the help of X-rays
• Pathological Anatomy: Study of structural changes associated with disease

Physiology

• It is the branch of biological science dealing with the study of the function and mechanism of different body parts
• Subdivisions include:
• Respiratory Physiology: Study of the function of lungs
• Renal Physiology: Study of the function of kidneys
• Immunology: Study of the function of the defence mechanism
• Neurophysiology: Study of the function of the nervous system.
• Pathophysiology: Study of functional changes linked with disease
• Cardiovascular Physiology: Study of the function of the heart and blood vessels
• Endocrinology: Study of hormones and body functions

Scope of HAP

• It provides the base for understanding the anatomy and physiology of different body parts
• It helps in the study of human evolution and development
• It allows understanding of the pathology of disease and pathological changes

Level of Structural Organization

• Living things consist of several levels of structural organization that are associated with one another in various ways
• They include:
• Chemical Level
• Cellular Level
• Tissue Level
• Organ Level
• System Level
• Organism Level

Chemical Level

• It is the lowest level of organization
• It includes atoms and molecules, such as nitrogen and phosphorus

Cellular Level

• Atoms and molecules combine to form cells
• Cells represent the basic structural and functional unit of life

Tissue Level

• Structurally and functionally similar groups of cells combine to form tissue
• Four basic types of tissue in the body are:
• Epithelial
• Muscular
• Connective
• Nervous

Organ Level

• Different kinds of tissues join together to form a structure of the body called an organ
• Examples include the heart, liver, lungs, brain, and bladder

System Level

• It is the level where different organs are joined together to form a body system
• The human body contains 11 systems:
• Integumentary
• Skeletal
• Muscular
• Nervous
• Endocrine
• Circulatory
• Respiratory
• Digestive
• Reproductive
• Lymphatic
• Urinary

Organism Level

• It is the highest level of organizational structure where all parts of the body are functioning with one another to complete the total organism

Basic Life Processes

• Life is mainly based on certain functions and processes important for a living being to stay healthy and survive
• Basic life processes include:
• Metabolism
• Respiration
• Reproduction
• Responsiveness
• Movement
• Growth

Metabolism

• Refers to all the chemical processes taking place in the body, by which the body changes food and drinks into energy
• It is of two types:
• Catabolism: The breakdown of complex chemical substances into simpler components
• Anabolism: Building up of complex chemical substances from smaller, simpler components

Respiration

• It is the process where living beings obtain energy (in the form of ATP) by taking oxygen and releasing carbon dioxide

Reproduction

• Defined as the biological process by which an organism gives birth or rises to a new organism

Responsiveness

• The ability of a living being to respond to any changes in the external or internal environment

Movement

• It is the process of movement of the whole body, an individual organ, or a cell from one position to another

Growth

• Defined as an increase in the mass and size of body or organs
• It occurs due to an increase in the number or size of cells

Homeostasis

• It is made up of two words 'Homeo' (same) and 'stasis' (state)
• Defined as the ability of the human body to maintain a constant internal environment by maintaining and balancing pH, temperature, and acid-base level
• The regulation/maintenance of homeostasis is governed by the feedback systems of the body

Feedback System

• When changes take place in the internal environment of the body, the body's feedback system works to take it back into the normal/equilibrium condition
• A feedback system includes three basic components:
• Receptor
• Control Centre
• Effector

Receptor

• A body structure that monitors/detects changes in the internal environment of the body

Control Centre

• It receives input from receptors and generates output in the form of nerve impulses, hormones, or other chemical signals

Effector

• A body structure that receives output from the Control Centre and responds to the commands of the Control Centre
• There are two types of feedback systems: positive and negative

Negative Feedback System

• It responds to reverse/decrease the changes in the internal environment
• Blood pressure regulation is an example
• When there is an increase in heart rate, blood pressure increases
• Baroreceptors activate and send input to the control centre through nerve impulses
• The brain collects input and sends output
• Blood vessels receive output and get dilated
• Blood pressure decreases, returning blood pressure and the body to homeostasis

Positive Feedback System

• It increases the change in the internal environment
• Normal childbirth is an example:
• Contraction of the uterus wall forces the baby's body towards the cervix
• Stretching of the cervix
• Stretch-sensitive nerve cells send input to the Control Centre through nerve impulses
• The Brain collects input and sends output by releasing oxytocin
• Uterine muscles contract more forcefully
• The baby's body stretches the cervix more
• Increased stretching of the cervix causes the release of more oxytocin, which results in more stretching of the cervix

Cellular Level of Organization

• The cell is the basic structural and functional unit of life
• Robert Hooke first discovered and named the cell in 1665
• Anton van Leeuwenhoek discovered the first living cell
• There are 200 different types of cells present in the body
• Cell Biology or Cytology studies cellular structure and function

Parts of a Cell

• The cell is divided into two major parts: plasma membrane and cell organelles

Plasma Membrane

• The cell membrane is a thin, flexible, elastic barrier or outer covering that separates the internal components of the cell from the external environment.
• A selectively permeable membrane allows only a few substances to pass through it.
• It is made up of:
• Protein (60-80%)
• Lipids (20-40%, 75% being phospholipids)
• Carbohydrates (1-2%)
• It contains a bilayer of phospholipids
• Phospholipid molecules have two parts:
• Head (hydrophilic)
• Tail (hydrophobic or lipophilic)
• Functions:
• Protection of cells
• Acts as a barrier to separating the cell's internal environment from that external organism
• Gives a specific shape to cells
• Regulates and controls the movement of substances
• Prevents the movement of other substances that can be harmful to the cell

Cytoplasm

• A gel-like substance present in the whole cell from the nucleus to the plasma membrane
• The fluid portion of the cytoplasm in which other cell organelles are suspended is called cytosol or intracellular fluid
• Cytosol contains water (75-90%), ions, amino acids, proteins, and lipids plus different inorganic substances and salts

Ribosomes

• Tiny granules composed of RNA and protein
• Synthesize proteins from amino acids using RNA, and are known as the 'Factory of Protein'
• There are two types:
• Free ribosomes (present freely in the cytosol)
• Membrane-bound ribosomes (attached with the endoplasmic reticulum)

Endoplasmic Reticulum

• A network of membranes is attached to the nucleus, and helps transport materials between cell organelles
• There are two types:
• Smooth ER: Does not contain ribosomes, synthesizes fats and oils
• Rough ER: Contains ribosomes, synthesizes protein

Golgi Apparatus/Body/Complex

• Present near the nucleus
• Consist of 4-6 flattened sacs (a bag-like structure) called cisterns, placed upon each other
• Proteins move from the endoplasmic reticulum to the Golgi apparatus
• The Golgi apparatus stores, modifies, and transports proteins across the cell

Mitochondria

• Known as the 'Power House of The Cell'
• Consist of two membrane-bound structures:
• Outer membrane (smooth)
• Inner membrane (folded)
• It performs cellular respiration, and during this process, energy is released (ATP) used by/ utilized by the cell for performing various activities

Lysosomes

• Membrane-bound structures filled with digestive enzymes
• Help clean the cell by digesting foreign materials and damaged cell organelles
• Also known as 'suicidal bags of cells' because when cell organelles get damaged, lysosomes burst and digest the whole cell

Nucleus

• Generally spherical or oval in shape, and the largest structure in the cell
• It controls all the activities done by the cell and is known as the 'Brain of the Cell'
• Consists of two parts:
• Nuclear membrane/Nuclear envelope
• Nucleoplasm

Nuclear Membrane/Nuclear Envelope

• It separates the nucleus from the cytoplasm
• It contains pores/space that permits the transfer of materials between cytoplasm and nucleoplasm

Nucleoplasm

• It is the liquid ground substance covered by the nuclear envelope
• It contains 'nucleolus' and 'chromatin Fibres/Materials'
• The nucleolus forms ribosomes, and chromatin material forms centrosomes

Transfer of Materials Across Plasma Membrane

• Transferring substances across the cell membrane is necessary to maintain normal functioning, and cell survival
• Substances move through the cell/plasma membrane by two major processes: passive and active transport

Passive Transport

• Substances move across the cell membrane from the area of higher concentration to the area of lower concentration
• No energy is required to move substances across the cell membrane
• There are three types: simple diffusion, facilitated diffusion, and osmosis

Simple Diffusion

• Substances simply move across the cell membrane from the area of higher concentration to the area of lower concentration
• It does not require any carrier protein

Facilitated Diffusion

• Molecules move from high concentration to low concentration with the help of carrier proteins
• Includes the movement of large molecules, glucose, and vitamins

Osmosis

• Defined as the movement of solvent molecules across a semi-permeable membrane
• The solvent is basically water; hence, osmosis can be defined as the movement of water molecules in and out of the semi- cell membrane/plasma membrane from a higher concentration to a lower concentration

Active Transport

• Defined as a process involving the movement of molecules from a region of lower concentration to a region of higher concentration using external energy
• The energy (ATP) is mainly obtained by the breakdown/hydrolysis of ATP
• There are two types: primary and secondary active

Primary Active Transport

• The energy is utilized by the breakdown of ATP
• Requires a carrier protein
• 40% of ATP consumed by body is used in primary active transport
• The sodium-potassium pump is an example

Secondary Active Transport

• The energy is used from the electrochemical gradient generated by active transport
• There are two types: symporter and antiporter

Symporter

• An active transport protein that transports two different molecules across the cell membrane in the same direction

Antiporter

• An active transport protein that transports two different molecules in opposite directions

Cell Division

• A process by which a parent cell divides into two daughter cells
• Also known as cell reproduction or cell multiplication
• Cell division takes place approximately every 24 hours
• There are two types of cell division: somatic cell division (mitosis) and reproductive cell division (meiosis)

Cell Cycle

• During cell division, DNA replication and cell growth take place
• It is a sequence of events or changes that takes place during the division of the cell into daughter cells

Need for Cell Division

• For the growth of an organism
• To replace old, dead, and injured cells
• For gamete formation

Phases of Cell Division/Cell Cycle

• A cell cycle or cell division involves two basic phases: Interphase and M-phase

Interphase

• The longest phase of cell division, taking almost 23 hours (95% of the cell division time)
• It is basically the preparation phase for cell division
• Consists of three phases: G1 phase, S phase, and G2 phase

G1 Phase

• Simply known as the 'First Growth Phase'
• In this phase, the cell is metabolically active and replicates most of its cell organelles except DNA
• The G1 phase lasts for 8-10 hours

S Phase

• Known as the 'Synthesis Phase'
• The interval between the G1 and G2 phases
• The cell makes an entire copy/replicates its DNA and centrosomes
• The S phase lasts about 8 hours

G2 Phase

• Termed as the 'Second Growth Phase'
• During this phase, cell growth continues, enzymes and other proteins are synthesized
• G2 phase lasts for 4-6 hours

M-Phase

• Is the final step in cell division, and is composed of two types: mitosis and meiosis

Mitosis/Somatic Cell Division

• Somatic cell division or mitosis is the type of cell division where the daughter cells produced are exactly similar to the parent cell, having the same number of chromosomes as the parent cell
• Mitosis occurs in whole-body cells except for germ cells and neuron cells
• It is also known as the 'Equational Division'
• Mitosis occurs in two stages: karyokinesis and cytokinesis

Karyokinesis

• It is the process of 'nuclear division'
• Occurs in four phases: Prophase, Metaphase, Anaphase, and Telophase

Prophase

• In early prophase, the chromatin fibre condenses and forms chromosomes in which two sister chromatids are attached together at the centromere
• Centrosomes replicate in the S-Phase and move toward opposite poles of the cell and start forming the 'Mitotic spindle' or 'Spindle Fibre'
• In late prophase, the nucleolus, endoplasmic reticulum, and other cell organelles start disappearing

Metaphase

• During metaphase, the nuclear envelope completely disintegrates
• Spindle fibres of the centrosome align the centromere of the sister chromatids at the centre of the cell

Anaphase

• The centromere splits and thus the two sister chromatids get separated and move towards the opposite pole of the cell
• Once separated, the chromatids are again termed as 'chromosomes'

Telophase

• The daughter chromosomes reach the opposite poles and spindle fibres disappear
• Chromosomes again start converging into 'chromatin fibres'

Cytokinesis

• It is the division of the cell's cytoplasm and organelles in newly formed cells
• Each new daughter cell again enters into the 'Interphase Stage', and cell division continues

Meiosis/Reproductive Cell Division

• Reproductive cell division or meiosis is the type of cell division where the daughter cells receive only half the chromosomes of the parental cell
• Meiosis occurs in germ cells/sex cells/reproductive cells founded in the male gonad (testes) and female gonad (ovary) to form gametes (sperm and ovum)
• It is also known as 'Reductional Division'
• Meiosis occurs in two successive stages: Meiosis I and Meiosis II

Meiosis I

• It consists of four phases: Prophase I, Metaphase I, Anaphase I, and Telophase I

Prophase I

• Firstly chromatin fibre is condensed which transforms into chromosomes which exist in a pair called “Homologous Chromosome Pair”
• In the last phase of Prophase I- there is an exchange of DNA ( genetic material) between paired Chromosomes For genetic Recombination

Metaphase I

• Metaphase - I Spindle fibre of Centrosome align the “Homologous chromosomes” at the centre of the Cell

Anaphase I

• Homologous Chromosome becomes Separated to move towards opposite Pole of the Cell

Telophase I

• A nuclear membrane forms around homologous Chromosome where Spindle fibre is disappeared which causes formation of two haploid cell Forms during The process of Cytokinesis

Meiosis II

• The process, starting where two new Daughter cells forms from Meiosis , immediately enters into Meiosis -II with 4 stages- -Prophase - II -Methaphase -II -Anaphase -II -Telophase -II

Prophase II

• The stages are prophase – II or newly formed daughter cell’s Nuclear membrane disappears with centromeres which formed Motitic Spindle

Metaphase II

• Metaphase-II stages are alignment in where the spindle fibers along with chromosomes (sister chromatids ) with centrosome at the centre of the Cell where the

Anaphase II

• Anaphase-II Centromers separate and sister chromatids also moves apart and towards opposite poles of the Cell

Telophase II

• At Telophase –II Stage where Spindle fibers disappears along with Nucleur Membrane which forms by separation of chromatids leading to process of Cytokinesis which causes Formation of four new Haploid

Cell Junctions

• A cell junction is simply the connection between two plasma membranes or two cells
• It can be observed between two cells or between a cell and the basement membrane
• It consists of multi-protein complexes that provide contact between two neighbouring cells
• Functions: helps in the attachment of cells, transfer of ions/substances, prevents movement of unwanted substances, and helps in cell communication

Types of Cell Junctions

• There are five different types of cell junctions:
• Tight junctions
• Adherens junctions
• Desmosomes
• Hemi-desmosomes
• Gap junctions

Tight Junctions

• Act as a barrier to prevent the movement of unwanted ions/substances across cells
• Cells of epithelial tissues that are found in the stomach, intestine, and urinary bladder, contain many tight junctions that prevent the leaking of components into blood

Adherens Junctions

• These are also called Belt desmosomes
• Contain plaque (a dense layer of protein)
• Glycoprotein helps to join the cells

Desmosomes

• These junctions keep neighbouring cells together
• Contain plaque and intermediate filaments (made of keratin)
• Glycoprotein helps in the attachment of cells

Hemidesmosomes

• Resemble desmosomes but do not attach to adjacent cells
• Basically attached to the basement membrane

Gap Junctions

• Specialized intercellular connections between cells and helps transfer of required ions/substances between two or more cells
• Allow the cells to communicate with one another

Cell Communication

• Also known as 'cell signalling'
• The ability of a cell to receive and send signals from and to another cell
• Important for the growth and development of cells, and maintaining homeostasis
• Communication includes:
• Ligand: the signalling molecule
• Receptors: the site where the receptors bind

Types of Cell Signalling

• Paracrine
• Autocrine
• Endocrine
• Direct

Paracrine Signalling

• Signalling in which the "target cell" is very close to "signaling cell" but not directly attached
• Plays an important role in growth and development

Autocrine Signalling

• The Cell signals to itself, releasing a ligand that binds to the receptor on its own surface
• Plays a key role in metastasis

Endocrine Signalling

• The target cell is too far from the signalling cell then releases its signals (ligands) into the bloodstream and act on target cells which this is called Endocrine signalling
• Signals are in the form of Hormones

Direct Signalling

• It occurs by transferring signal molecules across gap junctions between neighbouring cells

Tissue Level of Organization

• Tissue is defined as a group of cells having a similar structure and functions
• Histology is the branch of science that deals with the study of tissues

Types of Body Tissues

• According to structure and function, body tissues can be classified into four basic categories:
• Epithelial tissue
• Connective tissue
• Muscular tissue
• Nervous tissue

Epithelial Tissue

• Also known as 'Epithelium'
• Forms the outer covering of the body and internal organs/internal cavity
• Cells are closely packed in the form of continuous sheets having to intercellular space
• Cells are connected to the basement membrane by Hemidesmosomes
• Functions: protection, secretion, absorption, and excretion

Types of Epithelial Tissue

• Simple Epithelial Tissue

• Simple Cuboidal: Single layer of cube-shaped cells arranged on the basement membrane. Located in the lining of kidney tubules, pancreas, and covering ovaries. Functions in the transportation secretion and filtration

• Simple Squamous: Single layer of flattened cells arranged on the basement membrane. Located in the lining of the heart, blood vessels and air sacs of the lungs. Functions in absorption and filtration.

• Simple Columnar- single layer of rectangular-shaped cells arranged on the basement membrane. located in lining of entire digestive tractor, reproductive system, eyes, ears. functions in secretion, protection

• Stratified Epithelial Tissue

• Stratified Cuboidal: Consists of two or more layers of cube shaped cells attached on basement membrane. Located in the lining of sweat glands, male urethra. Functions in secretion, protection

• Stratified Squamous: Consists of multiple layers of flattened shape ceils located in the skin, mouth, throat, vagina. Functions in protection and because there is keratin the skin is waterproof

• Stratified Columnar: Consists of several layers of rectangular. Located in Mucous membrane, lining of eyelids. Functions in protections and secretion

Connective Tissue

• Connects, supports, and binds different tissues and organs of the body
• Most abundant and widely distributed system in the body
• Cells are loosly packed huge inter cellular space

Composition of Connective Tissue

• Consists of Cells, Fibres, and Ground Substances

Connective Tissue

• Consist of Fibroblast, Macrophages, Plasma Cells, Mast Cells and WBCs and Adipocytes

Types of fibres

• There are 3 in Total Collagen, Elastic and Reticular fibres

Collagen Fibres

• Collagen fibres made of Collagen type 1 is non- branched provides Very Strong

Elastic Fibres

• Made of elastin branched as well in elastic nature to make thin and provide elasticity

Reticular Fibres

• The Reticular fibre made of Collagen type III that also branched along with glycoprotein coatings to make thin to provide support

Ground Substances

• Gel like substance contains cells fibres are suspended. Also compose water and sulphate water and glycoproteins

Function of Connective Tissue

• Connect several body tissues while provides protection to body organs giving support for structural framework as well as transportation for fat storage

Types of Connective Tissue

• Connective tissue have loose, and Special tissues

Loose Connective Tissue

• loose connect contain over the body loose fibre semi fluid matrix that helps in Proportion helps with ground cell that are further classified

There are 3 types classified Under loose connective tissues

• Areoral: collagen fiber elastic fibre and kind that also consist of cells to located belo skin to provide support to muscle structure
• Adipose: tissue contains fibroblast that protect organ from heat near kind with collagen structure
• Reticular Fibres: forms from organ blood vessel

Dense Connective Tissue

• closely packed to show higher content while cell have to main sub categories that make Irregular and regular dense Tissue

Regular Tissue

• Fiber is parallel to attach muscle with a bone to give attachment

Specialized Connective Tissue

• The tissues help to maintain organ in form. Support system

• Cartilage

• Is supportive in correct posture to maintains system organs helps too

• Bone

• Made bone matrix supports collagen organic salt and its hardness and main of body

• Blood

• The blood is fluid for type that is made of plasma to transport in Cell

Muscular Tissue

• Also is known as ‘Muscle Fibres” that make energy by using elongated cells and force
• Those Muscle made for moving for stability posture and production heat

Types of cell

• There are three main types of tissue such -skeletal (voluntary), -smooth, tissues, -cardiac Tissues

Skeletal

• Cylinder (shaped) tissues are mostly connected and multi for volentuntary

Smooth

• Involuntary- the spindle that contains one single is uninucleated that is striked

Cardiac tissues

• Found with out single in heart that is involuntary when strained

Nervous Tissue

• Is one of the human body main tissues is more than million (100,000,000) is main tissue . Consist if Nerve Cells Neurons Or Glial Cells

Functions of nervous system

• The Main function to produce protect neuron for support impulse impulse where is main function is maintain transmot nervous

Nerve Cell or Neuron

• main fundamental brain that makes body sell also terminals

Neurons can defined by

• Cell body- Nucleus
• Dentrites-Structure to Nervous to main receiver with other messages -Ation - The carrier (impulses)
• Axial Terminals - The Axion is signals with main signals