Notes for science olympiad | Cheat Sheet Biology

Muscular System The muscular system is comprised of three types of muscles: smooth muscles, skeletal muscles,

and cardiac muscles. Smooth muscles are found in the walls of internal organs and help with involuntary

contractions (sheets). Skeletal muscles are commonly attached to bones and are responsible for voluntary

movement (striated). Cardiac muscles, found only in the heart's walls, cause the heart to beat and pump

blood (striated, bundles).

Muscle Fibers: Type I (slow oxidative)- use oxygen to generate energy for muscle contractions over a long period

and are not easily tired. Type IIa (Fast Oxidative): Use oxygen to generate energy for contractions, but

contractions are higher tension than type 1 ﬁbers. Type IIx (Fast Glycotic): Do not use oxygen to generate energy.

Instead, store energy for short bursts of movement.

Contraction: Caused when the brain sends signals to motor neurons, inducing an action potential sent to the

neuromuscular junction. This propagates the diﬀusion of acetylcholine into muscle ﬁber receptors, initiating

contraction.

Neuromuscular junction: A type of synapse where neuronal signals from the brain or spinal cord interact with skeletal muscle ﬁbers, causing contraction.

Motor neurons transmit signals to the neuromuscular junction, and the brain sends signals via the spinal cord.

Musculoskeletal System: Skeletal and muscular systems work in tandem to support movement and strength across the body. Cartilage acts as a shock

absorber, ligaments stabilize joints, and tendons connect the skeletal system to the muscular system by connecting muscle to bone.

Muscle Origin and Insertion: Each muscle has an origin (attached to a ﬁxed bone) an insertion (attached to a movable bone)

and a function (the movement it causes when it contracts)

Exercise and aging: Exercise increases antioxidant response, decreases age-related oxidative stress and pro-inﬂammatory

signals, and promotes the activation of anabolic and mitochondrial biogenesis pathways in skeletal muscles. Muscles lose size

and strength as we age, which can contribute to fatigue, weakness, and reduced tolerance to exercise.

Poliomyelitis is a viral infection that targets motor neurons in the spinal cord and brainstem, leading to muscle weakness and

paralysis. Although largely eradicated, post-polio syndrome can cause new muscle weakness decades after the initial

infection. Muscular Dystrophies are a group of genetic disorders characterized by progressive muscle degeneration and

weakness. These conditions result from mutations aﬀecting proteins necessary for muscle health, leading to diﬃculties with

mobility and, in severe cases, respiratory and cardiac complications. Myasthenia Gravis is an autoimmune disorder where

antibodies block or destroy receptors for acetylcholine, a neurotransmitter essential for muscle contraction. This results in

muscle weakness that worsens with activity and improves with rest. Tetanus is caused by a toxin produced by the bacterium

Clostridium tetani. The toxin interferes with normal muscle contractions, leading to severe

and painful muscle spasms, often starting in the jaw (lockjaw) and spreading to other parts

of the body4. Myositis refers to inﬂammation of the muscles, often due to autoimmune

conditions. It causes muscle weakness and pain and can aﬀect various muscle groups,

including those involved in movement and breathing.

Muscle and tendon injuries such as strains and tendinitis can result from overuse or

sudden movements, causing pain, swelling, and reduced mobility. To prevent these

injuries, it's important to warm up, use correct techniques, and gradually increase exercise

intensity. Wearing proper footwear, maintaining overall ﬁtness, staying hydrated, and

allowing for adequate rest between workouts is also crucial for muscle and tendon health.

Skeletal system: The axial skeleton is composed of the bones in the head, neck, back, and

chest. The appendicular skeleton includes everything else.

Joints: Joints in the human body are classiﬁed into three main types based on their

structure and function. Fibrous joints include sutures, which are immovable joints found

in the skull; gomphoses, which hold teeth in place in the jaw; and syndesmoses, which

connect two bones, such as the tibia and ﬁbula. Cartilaginous joints are slightly movable

and include synchondroses, where bones are joined by hyaline cartilage, and symphyses,

where bones are joined by ﬁbrocartilage, providing strength and ﬂexibility. Synovial joints

are the most movable type and include hinge joints (e.g., elbow and knee) that allow

movement in one plane, ball-and-socket joints (e.g., shoulder and hip) that allow movement

in multiple planes, pivot joints (e.g., between the ﬁrst and second cervical vertebrae) that

allow rotational movement, saddle joints (e.g., thumb) that allow movement in two planes,

plane joints (e.g., carpals of the wrist) that allow sliding movements, and condyloid joints

(e.g., wrist) that allow movement but no rotation.

Muscles and ligaments surrounding the joints

Quadriceps: Structure: Group of four muscles (rectus femoris, vastus lateralis, vastus

medialis, vastus intermedius) located at the front of the thigh. Function: Extends the knee

and ﬂexes the hip. Hamstrings: Structure: Group of three muscles (biceps femoris,

semitendinosus, semimembranosus) located at the back of the thigh.Function: Flexes the

knee and extends the hip.Deltoid: Structure: Triangular muscle covering the

shoulder.Function: Abducts, ﬂexes, and extends the arm. Rotator Cuﬀ Muscles:

Structure: Group of four muscles (supraspinatus, infraspinatus, teres minor,

subscapularis) surrounding the shoulder joint.Function: Stabilizes the shoulder joint and

allows for rotation and lifting of the arm. Gastrocnemius: Structure: Calf muscle with two

heads (medial and lateral) that merge into the Achilles tendon.Function: Plantar ﬂexes the

foot and ﬂexes the knee. Ligaments.Anterior Cruciate Ligament (ACL) Structure:

Ligament inside the knee joint, connecting the femur to the tibia.Function: Prevents the

tibia from sliding out in front of the femur and provides rotational stability.Posterior

Cruciate Ligament (PCL): Structure: Ligament inside the knee joint, connecting the femur

to the tibia.Function: Prevents the tibia from sliding backward under the femur.Medial

Collateral Ligament (MCL): Structure: Ligament on the inner side of the knee, connecting

the femur to the tibia.Function: Provides stability to the inner knee.Lateral collateral

Ligament (LCL): Structure: Ligament on the outer side of the knee, connecting the femur

to the ﬁbula.Function: Provides stability to the outer knee.Achilles Tendon: Structure:

Tendon connecting the calf muscles (gastrocnemius and soleus) to the heel bone.Function:

Enables plantar ﬂexion of the foot.

Bone Structure: Bones are composed of an outer layer of compact bone and an inner layer

of spongy bone, which contains trabeculae and bone marrow. The diaphysis is the bone's

long axis, consisting of compact bone surrounding the medullary cavity, which contains

either red or yellow bone marrow. The ends of the bone are called epiphyses, covered with

articular cartilage. The metaphysis is where the diaphysis and the epiphysis meet and contain the epiphyseal line.

The periosteum, covering the external surface of bones, consists of a ﬁbrous layer and an osteogenic layer secured

by Sharpey's ﬁbers. The endosteum covers the internal surface of bones. Osteons are the structural units of long

bones, containing Haversian canals and perforating canals to supply nutrients.

Skeletal Cartilage: Cartilage, mainly composed of water, is strong, resilient, and heals poorly due to a lack of blood

vessels and nerves. Found in the epiphyseal plate and joints for shock absorption, it is replaced by bone as we age. Chondroblasts develop into chondrocytes, which maintain the cartilage’s extracellular matrix. Cartilage is surrounded by the

perichondrium, preventing outward expansion when compressed. It grows through appositional (new matrix at the surface) and interstitial (matrix expansion from within) growth. Hyaline cartilage is the most abundant, ﬂexible, and resilient,

found in various locations like joints and the respiratory tract. Elastic cartilage, with more elastic ﬁbers, is found in the ear and epiglottis. Fibrocartilage, strong and compressible, is found in the knee menisci, intervertebral disks, and pubic

symphysis.

Vertebrae: The vertebral column is comprised of 26 irregular bones that form a ﬂexible, curved structure, serving as the axial support for the trunk and transmitting its weight to the lower limbs. It also surrounds and protects the spinal cord

and provides attachment points for the ribs and muscles of the back and neck. In early development, it consists of 33 vertebrae, with nine of them fusing to form the sacrum and coccyx. The seven cervical vertebrae, from C1 to C7, support the

neck, with C1 (the atlas) and C2 (the axis) supporting the head and pivoting the neck, respectively.. The twelve thoracic vertebrae, T1 to T12, are attached to the ribs, while the ﬁve lumbar vertebrae, L1 to L5, provide ﬂexibility and stability to the

trunk. The sacrum is formed by the fusion of ﬁve vertebrae (S1 to S5) during adulthood, and the coccyx is a vestigial structure formed by the fusion of four vertebrae.

Fractures can be classiﬁed using the Salter-Harris classiﬁcation system. The mnemonic used for Salter-Harris fractures is “Straight across, Above, Lower (or below), Two (or Through), and ERasure of growth plate (or cRush).” Approximately 5%

of Salter-Harris fractures are classiﬁed as Type I. These fractures are the least concerning and heal the quickest. This occurs when the fracture passes through the growth plate. About 75% of Salter-Harris fractures are classiﬁed as Type II. This

involves fracturing of the growth plate, or physis, and the metaphysis. These fractures heal quickly and only minimally prohibit bone growth. About 10% of Salter-Harris fractures are classiﬁed as Type III. This involves fracturing of the growth

plate, or physis, and the epiphysis. When this occurs, the joint needs to be reduced and ﬁxated. These fractures may result in growth deformity. About 10% of Salter-Harris fractures are classiﬁed as Type IV. This occurs when the fracture

passes through the growth plate, or physis, the metaphysis, and the epiphysis. These fractures may result in growth

disturbances and angular deformities. Less than 5% of Salter-Harris fractures are classiﬁed as Type V. This involves

compression or crushing of the growth plate or physis. This usually results in growth deformities and disturbances.

Integumentary system The integumentary system is composed of the skin, hair, nails, and some glands. It is the body’s

ﬁrst line of defense against the outside world. It’s functions are to protect te body from injuries and pathogens, to

regulate heat exchange with the environment, to synthesize Vitamin D3 and store lipids, to facilitate sensory

reception, to excrete and secrete various substances, and to protect the body from dehydration.

Skin The skin has 3 layers: the epidermis (outer epithelial layer), the dermis (thicker connective tissue layer), and the

hypodermis (connective tissues that anchor skin and absorb shock). The epidermis consists mainly of keratinized

stratiﬁed squamous epithelium and has 4 major cell types: Keratinocytes produce keratin, hair, and nails. Melanocytes

produce melanin, determining skin color. Langerhans cells are macrophages involved in immune response. Merkel

cells function in touch sensation. Skin is classiﬁed as thin (hairy) or thick (hairless). Thin skin covers most body

regions except palms, ﬁngertips, and soles; it is 1-2 mm thick, has fewer receptors and sudoriferous glands, and

more sebaceous glands. Thick skin covers palms, ﬁngertips, and soles; it has more receptors and sudoriferous glands,

and fewer sebaceous glands. Skin ridges (e.g., ﬁngerprints) are due to well-developed dermal papillae and aid in grip

and object manipulation. The epidermis has four layers in thin skin and ﬁve in thick skin. Starting from the deepest,

the layers are the stratum basale, which is connected to the basement membrane by hemidesmosomes and contains

basal cells that continuously divide to produce keratinocytes, melanocytes that produce melanin, and nervous

receptors. The stratum spinosum is composed of 8-10 layers of keratinocytes connected by desmosomes, with many

melanosomes and dendritic cells. The stratum granulosum is where keratinization begins, producing keratin for

upper layers, and keratinocytes here start to die due to lack of nutrients. The stratum lucidum is present only in thick

skin (ﬁngertips, palms, soles) and is a thin, translucent layer. The outermost layer, the stratum corneum, is composed

of 20-30 layers of dead, ﬂattened keratinocytes (keratinized cells) that protect the dermis. These cells are tightly

attached by desmosomes, causing skin to peel in sheets after sunburn.. Skin color is inﬂuenced by three major

pigments: carotene, melanin, and hemoglobin. Carotene, a yellow-orange pigment, can turn light-skinned

individuals’ skin orange when consumed in large amounts and is synthesized into Vitamin A for epithelial cell

maintenance. Melanin, produced by melanocytes, varies from yellow to brown and protects against UV radiation. It

has two types: eumelanin (brownish-black) and pheomelanin (reddish-yellow). Melanin production increases with sun

exposure, peaking after about 10 days. Hemoglobin, a red pigment in blood, gives skin its red tint when oxygenated

and a blue-purple tint when deoxygenated. Conditions like vitiligo, where melanocytes stop producing melanin, aﬀect

skin color but are only cosmetic. The dermis, beneath the epidermis, has two layers: the papillary layer, which supplies

nutrients, and the reticular layer, which provides elasticity and strength. Collagen ﬁbers in the dermis degrade with UV

exposure, causing wrinkles. The integumentary system also synthesizes Vitamin D3, essential for calcium uptake in

bones, from a cholesterol-based steroid with the help of UV radiation.

Hair, Nails, and Glands: Hair, made of keratin, develops before birth. Hair shaft shapes determine texture: ﬂat and

ribbonlike for kinky hair, oval for silky and wavy hair, and round for straight and coarse hair. There are three main

types of body hair: terminal (thick, coarse hairs growing during puberty), lanugo (ﬁne, soft hairs on infants,

Partial preview of the text

Download Notes for science olympiad and more Cheat Sheet Biology in PDF only on Docsity!

Muscular System The muscular system is comprised of three types of muscles: smooth muscles, skeletal muscles, and cardiac muscles. Smooth muscles are found in the walls of internal organs and help with involuntary contractions (sheets). Skeletal muscles are commonly attached to bones and are responsible for voluntary movement (striated). Cardiac muscles, found only in the heart's walls , cause the heart to beat and pump blood (striated, bundles).

Muscle Fibers: Type I (slow oxidative)- use oxygen to generate energy for muscle contractions over a long period and are not easily tired. Type IIa (Fast Oxidative): Use oxygen to generate energy for contractions, but contractions are higher tension than type 1 fibers. Type IIx (Fast Glycotic): Do not use oxygen to generate energy. Instead, store energy for short bursts of movement.

Contraction: Caused when the brain sends signals to motor neurons, inducing an action potential sent to the neuromuscular junction. This propagates the diffusion of acetylcholine into muscle fiber receptors, initiating contraction. Neuromuscular junction: A type of synapse where neuronal signals from the brain or spinal cord interact with skeletal muscle fibers, causing contraction. Motor neurons transmit signals to the neuromuscular junction, and the brain sends signals via the spinal cord. Musculoskeletal System: Skeletal and muscular systems work in tandem to support movement and strength across the body. Cartilage acts as a shock absorber, ligaments stabilize joints, and tendons connect the skeletal system to the muscular system by connecting muscle to bone. Muscle Origin and Insertion: Each muscle has an origin (attached to a fixed bone) an insertion (attached to a movable bone) and a function (the movement it causes when it contracts) Exercise and aging: Exercise increases antioxidant response, decreases age-related oxidative stress and pro-inflammatory signals, and promotes the activation of anabolic and mitochondrial biogenesis pathways in skeletal muscles. Muscles lose size and strength as we age, which can contribute to fatigue, weakness, and reduced tolerance to exercise. Poliomyelitis is a viral infection that targets motor neurons in the spinal cord and brainstem, leading to muscle weakness and paralysis. Although largely eradicated, post-polio syndrome can cause new muscle weakness decades after the initial infection. Muscular Dystrophies are a group of genetic disorders characterized by progressive muscle degeneration and weakness. These conditions result from mutations affecting proteins necessary for muscle health, leading to difficulties with mobility and, in severe cases, respiratory and cardiac complications. Myasthenia Gravis is an autoimmune disorder where antibodies block or destroy receptors for acetylcholine, a neurotransmitter essential for muscle contraction. This results in muscle weakness that worsens with activity and improves with rest. Tetanus is caused by a toxin produced by the bacterium Clostridium tetani. The toxin interferes with normal muscle contractions, leading to severe and painful muscle spasms, often starting in the jaw (lockjaw) and spreading to other parts of the body 4. Myositis refers to inflammation of the muscles, often due to autoimmune conditions. It causes muscle weakness and pain and can affect various muscle groups, including those involved in movement and breathing.

Muscle and tendon injuries such as strains and tendinitis can result from overuse or sudden movements, causing pain, swelling, and reduced mobility. To prevent these injuries, it's important to warm up, use correct techniques, and gradually increase exercise intensity. Wearing proper footwear, maintaining overall fitness, staying hydrated, and allowing for adequate rest between workouts is also crucial for muscle and tendon health.

Skeletal system: The axial skeleton is composed of the bones in the head, neck, back, and chest. The appendicular skeleton includes everything else. Joints: Joints in the human body are classified into three main types based on their structure and function. Fibrous joints include sutures, which are immovable joints found in the skull; gomphoses, which hold teeth in place in the jaw; and syndesmoses, which connect two bones, such as the tibia and fibula. Cartilaginous joints are slightly movable and include synchondroses, where bones are joined by hyaline cartilage, and symphyses, where bones are joined by fibrocartilage, providing strength and flexibility. Synovial joints are the most movable type and include hinge joints (e.g., elbow and knee) that allow movement in one plane, ball-and-socket joints (e.g., shoulder and hip) that allow movement in multiple planes, pivot joints (e.g., between the first and second cervical vertebrae) that allow rotational movement, saddle joints (e.g., thumb) that allow movement in two planes, plane joints (e.g., carpals of the wrist) that allow sliding movements, and condyloid joints (e.g., wrist) that allow movement but no rotation. Muscles and ligaments surrounding the joints Quadriceps: Structure : Group of four muscles (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius) located at the front of the thigh. Function : Extends the knee and flexes the hip. Hamstrings: Structure : Group of three muscles (biceps femoris, semitendinosus, semimembranosus) located at the back of the thigh. Function : Flexes the knee and extends the hip.Deltoid: Structure : Triangular muscle covering the shoulder. Function : Abducts, flexes, and extends the arm. Rotator Cuff Muscles: Structure : Group of four muscles (supraspinatus, infraspinatus, teres minor, subscapularis) surrounding the shoulder joint. Function : Stabilizes the shoulder joint and allows for rotation and lifting of the arm. Gastrocnemius: Structure : Calf muscle with two heads (medial and lateral) that merge into the Achilles tendon. Function : Plantar flexes the foot and flexes the knee. Ligaments.Anterior Cruciate Ligament (ACL) Structure : Ligament inside the knee joint, connecting the femur to the tibia. Function : Prevents the tibia from sliding out in front of the femur and provides rotational stability. Posterior Cruciate Ligament (PCL): Structure : Ligament inside the knee joint, connecting the femur to the tibia. Function : Prevents the tibia from sliding backward under the femur. Medial Collateral Ligament (MCL): Structure : Ligament on the inner side of the knee, connecting the femur to the tibia. Function : Provides stability to the inner knee .Lateral collateral Ligament (LCL): Structure : Ligament on the outer side of the knee, connecting the femur to the fibula. Function : Provides stability to the outer knee. Achilles Tendon: Structure: Tendon connecting the calf muscles (gastrocnemius and soleus) to the heel bone. Function : Enables plantar flexion of the foot. Bone Structure: Bones are composed of an outer layer of compact bone and an inner layer of spongy bone, which contains trabeculae and bone marrow. The diaphysis is the bone's long axis, consisting of compact bone surrounding the medullary cavity, which contains either red or yellow bone marrow. The ends of the bone are called epiphyses, covered with articular cartilage. The metaphysis is where the diaphysis and the epiphysis meet and contain the epiphyseal line. The periosteum, covering the external surface of bones, consists of a fibrous layer and an osteogenic layer secured by Sharpey's fibers. The endosteum covers the internal surface of bones. Osteons are the structural units of long bones, containing Haversian canals and perforating canals to supply nutrients. Skeletal Cartilage: Cartilage, mainly composed of water, is strong, resilient, and heals poorly due to a lack of blood vessels and nerves. Found in the epiphyseal plate and joints for shock absorption, it is replaced by bone as we age. Chondroblasts develop into chondrocytes, which maintain the cartilage’s extracellular matrix. Cartilage is surrounded by the perichondrium, preventing outward expansion when compressed. It grows through appositional (new matrix at the surface) and interstitial (matrix expansion from within) growth. Hyaline cartilage is the most abundant, flexible, and resilient, found in various locations like joints and the respiratory tract. Elastic cartilage, with more elastic fibers, is found in the ear and epiglottis. Fibrocartilage, strong and compressible, is found in the knee menisci, intervertebral disks, and pubic symphysis. Vertebrae: The vertebral column is comprised of 26 irregular bones that form a flexible, curved structure, serving as the axial support for the trunk and transmitting its weight to the lower limbs. It also surrounds and protects the spinal cord and provides attachment points for the ribs and muscles of the back and neck. In early development, it consists of 33 vertebrae, with nine of them fusing to form the sacrum and coccyx. The seven cervical vertebrae, from C1 to C7, support the neck, with C1 (the atlas) and C2 (the axis) supporting the head and pivoting the neck, respectively.. The twelve thoracic vertebrae, T1 to T12, are attached to the ribs, while the five lumbar vertebrae, L1 to L5, provide flexibility and stability to the trunk. The sacrum is formed by the fusion of five vertebrae (S1 to S5) during adulthood, and the coccyx is a vestigial structure formed by the fusion of four vertebrae.

Fractures can be classified using the Salter-Harris classification system. The mnemonic used for Salter-Harris fractures is “ S traight across, A bove, L ower (or below), T wo (or T hrough), and ER asure of growth plate (or c R ush).” Approximately 5% of Salter-Harris fractures are classified as Type I. These fractures are the least concerning and heal the quickest. This occurs when the fracture passes through the growth plate. About 75% of Salter-Harris fractures are classified as Type II. This involves fracturing of the growth plate, or physis, and the metaphysis. These fractures heal quickly and only minimally prohibit bone growth. About 10% of Salter-Harris fractures are classified as Type III. This involves fracturing of the growth plate, or physis, and the epiphysis. When this occurs, the joint needs to be reduced and fixated. These fractures may result in growth deformity. About 10% of Salter-Harris fractures are classified as Type IV. This occurs when the fracture passes through the growth plate, or physis, the metaphysis, and the epiphysis. These fractures may result in growth disturbances and angular deformities. Less than 5% of Salter-Harris fractures are classified as Type V. This involves compression or crushing of the growth plate or physis. This usually results in growth deformities and disturbances.

Integumentary system The integumentary system is composed of the skin, hair, nails, and some glands. It is the body’s first line of defense against the outside world. It’s functions are to protect te body from injuries and pathogens, to regulate heat exchange with the environment, to synthesize Vitamin D3 and store lipids, to facilitate sensory reception, to excrete and secrete various substances, and to protect the body from dehydration. Skin The skin has 3 layers: the epidermis (outer epithelial layer), the dermis (thicker connective tissue layer), and the hypodermis (connective tissues that anchor skin and absorb shock). The epidermis consists mainly of keratinized stratified squamous epithelium and has 4 major cell types: Keratinocytes produce keratin, hair, and nails. Melanocytes produce melanin, determining skin color. Langerhans cells are macrophages involved in immune response. Merkel cells function in touch sensation. Skin is classified as thin (hairy) or thick (hairless). Thin skin covers most body regions except palms, fingertips, and soles; it is 1-2 mm thick, has fewer receptors and sudoriferous glands, and more sebaceous glands. Thick skin covers palms, fingertips, and soles; it has more receptors and sudoriferous glands, and fewer sebaceous glands. Skin ridges (e.g., fingerprints) are due to well-developed dermal papillae and aid in grip and object manipulation. The epidermis has four layers in thin skin and five in thick skin. Starting from the deepest, the layers are the stratum basale , which is connected to the basement membrane by hemidesmosomes and contains basal cells that continuously divide to produce keratinocytes, melanocytes that produce melanin, and nervous receptors. The stratum spinosum is composed of 8-10 layers of keratinocytes connected by desmosomes, with many melanosomes and dendritic cells. The stratum granulosum is where keratinization begins, producing keratin for upper layers, and keratinocytes here start to die due to lack of nutrients. The stratum lucidum is present only in thick skin (fingertips, palms, soles) and is a thin, translucent layer. The outermost layer, the stratum corneum, is composed of 20-30 layers of dead, flattened keratinocytes (keratinized cells) that protect the dermis. These cells are tightly attached by desmosomes, causing skin to peel in sheets after sunburn.. Skin color is influenced by three major pigments: carotene, melanin, and hemoglobin. Carotene , a yellow-orange pigment, can turn light-skinned individuals’ skin orange when consumed in large amounts and is synthesized into Vitamin A for epithelial cell maintenance. Melanin , produced by melanocytes, varies from yellow to brown and protects against UV radiation. It has two types: eumelanin (brownish-black) and pheomelanin (reddish-yellow). Melanin production increases with sun exposure, peaking after about 10 days. Hemoglobin , a red pigment in blood, gives skin its red tint when oxygenated and a blue-purple tint when deoxygenated. Conditions like vitiligo, where melanocytes stop producing melanin, affect skin color but are only cosmetic. The dermis, beneath the epidermis, has two layers: the papillary layer, which supplies nutrients, and the reticular layer, which provides elasticity and strength. Collagen fibers in the dermis degrade with UV exposure, causing wrinkles. The integumentary system also synthesizes Vitamin D3, essential for calcium uptake in bones, from a cholesterol-based steroid with the help of UV radiation. Hair, Nails, and Glands: Hair, made of keratin, develops before birth. Hair shaft shapes determine texture: flat and ribbonlike for kinky hair, oval for silky and wavy hair, and round for straight and coarse hair. There are three main types of body hai r: terminal (thick, coarse hairs growing during puberty), lanugo (fine, soft hairs on infants,

indicating anorexia nervosa in adults), and vellus (short, fine hairs on most of the body, thinner than lanugo). Hair follicles extend from the epidermis into the dermis or hypodermis, forming a hair bulb at the deep end. The hair bulb contains a hair papilla with capillaries supplying nutrients. The follicle’s outer wall is a connective tissue sheath, with a glassy membrane in the middle and an epithelial root sheath inside. The hair matrix, originating from the hair bulge, produces new hair cells. Arrector pili muscles attached to follicles cause goosebumps when contracted. Hair grows about 2.5 mm per week, with each follicle undergoing growth (anagen), regressive (catagen), and resting (telogen) phases. Scalp hair has longer anagen phases than eyebrow hair, explaining the length difference. Each nail has a free edge , also known as a nail plate , as well as a proximal root. The deeper layers of the epidermis extend beneath the nail to form the nail bed. The thickened portion of the nail bed is the nail matrix , which is responsible for nail growth. As nail cells are produced in the matrix, they keratinize and slide distally over the nail bed. Nails are mostly pink because of the capillaries supplying the nail bed. The white crescent that lies over the nail matrix is the lunula. The borders of the nails are overlapped by skin folds, called nail folds. The eponychium , or cuticle , is the projection of the proximal nail fold onto the nail body. Below the free edge is the hyponychium , which is where dirt and debris accumulate. The integumentary system has two main types of glands: sebaceous glands, which produce oil, and sudoriferous glands, which produce sweat. Thin skin has more sebaceous glands and fewer sudoriferous glands, while thick skin has the opposite. Sebaceous glands secrete sebum to lubricate hair and skin and are found everywhere except thick skin areas like palms and soles. Acne is caused by inflammation of these glands. Sudoriferous glands, found mostly in thick skin, include apocrine and eccrine glands. Apocrine glands, developing during puberty, are located in areas like the ear canal, underarms, and pubic regions, and include modified glands like mammary and ceruminous glands. Eccrine glands, present from birth, secrete sweat composed of water and sodium chloride and are found everywhere except thick skin. Homeostatic Imbalances: Burns are integumentary disorders caused by intense heat, radiation, electricity, or friction, and are classified as first, second, or third-degree based on damage depth. First-degree burns affect the epidermis and papillary dermis, appearing dry and red with small blisters. Second-degree burns destroy the epidermis and involve all dermal layers, making the skin look shiny and wet. Third-degree burns damage all skin layers, appearing charred and often requiring skin grafts. Allergens trigger rapid immune responses, while infections invade dermal tissue. Dermatitis is skin inflammation, with eczema causing itchy, inflamed skin, often hereditary and exacerbated by environmental factors. Contact dermatitis results from allergens or irritants, and seborrheic dermatitis causes scaly patches and itching. Psoriasis, a condition with red, flaky patches, has types like plaque, guttate, inverse, pustular, and erythrodermic, with various triggers and treatments. Skin cancer, the most common US cancer, includes basal cell carcinoma, squamous cell carcinoma, and melanoma, caused by DNA damage from sunlight. The ABCD test helps identify skin cancer: asymmetry, uneven borders, color variations, and diameter over 6 mm.canal, underarms, and pubic regions, and include modified glands like mammary and ceruminous glands. Eccrine glands, present from birth, secrete sweat composed of water and sodium chloride and are found everywhere except thick skin.

Notes for science olympiad, Cheat Sheet of Biology

Related documents

Partial preview of the text

Download Notes for science olympiad and more Cheat Sheet Biology in PDF only on Docsity!