Results for "cytoplasm"

Cytoplasm

2.2. HET CYTOPLASMA

System Interactions in Animals Tools Finish System Interactions in Animals The human body is made of many different organ systems. Each system performs unique functions for the body, but the systems also interact with each other to perform more complex functions. Major Organ Systems Body Systems In humans, cells, tissues, and organs group together to form organ systems. These systems each perform different functions for the human body. The major organ systems and their functions in humans include: The Nervous System — The nervous systems consists of two parts. The central nervous system consists of the brain and spinal cord, while the peripheral nervous system consists of nerves that connect the central nervous system to other parts of the body. The brain plays an important role in interpreting the information picked up by the sensory system. It helps in producing a precise response to the stimuli. It also controls bodily functions such as movements, thoughts, speech, and memory. The brain also controls many processes related to homeostasis in the body. The spinal cord connects to the brain through the brainstem. From the brainstem, the spinal cord extends to all the major nerves in the body. The spinal cord is the origin of spinal nerves that branch out to various body parts. These nerves help in receiving and transmitting signals from various body parts. The spinal cord helps in reflex actions of the body The smallest unit of the nervous system is the nerve cell, or neuron. Neurons communicate with each other and with other cells by producing and releasing electrochemical signals known as nerve impulses. Neurons consist of the cell body, the dendrites, and the axon. The cell body consists of a nucleus and cytoplasm. Dendrites are specialized branch-like structures that help in conducting impulses to and from the various body parts. Axons are long, slender extensions of the neuron. Each neuron possesses just a single axon. Its function is to carry the impulses away from the cell body to other neurons. The Circulatory System — The circulatory (or cardiovascular) system is composed of the heart, arteries, veins, and capillaries. The circulatory system is responsible for transporting blood to and from the lungs so that gas exchange can take place. As the circulatory system pumps blood throughout the body, dissolved nutrients and wastes are also delivered to their destinations. The heart is a muscular organ roughly the size of an adult human's closed fist. It is present behind the breastbone, slightly to the left. It consists of four chambers: right atrium, left atrium, right ventricle, and left ventricle. The heart receives deoxygenated blood from the body and pumps this blood to the lugs, where it is oxygenated. The oxygen-rich blood reenters the heart and is then pumped back through the body. The circulatory system is responsible for transporting blood to and from the lungs so that gas exchange can take place. As the circulatory system pumps blood throughout the body, dissolved nutrients and wastes are also delivered to their destinations. Blood circulation takes place through blood vessels. Blood vessels are tubular structures that form a network within the body and transport blood to each tissue. There are three major types of blood vessels: veins, arteries, and capillaries. Veins carry deoxygenated blood from the body to the heart, except for pulmonary veins, which carry oxygenated blood from the lungs to the heart. Arteries carry oxygenated blood from the heart to different organs, except for the pulmonary artery, which carries deoxygenated blood from the heart to the lungs. The arteries branch out to form capillaries. These capillaries are thin-walled vessels through which nutrients and wastes are exchanged with cells. The Respiratory System — The main structures of the respiratory system are the trachea (windpipe), the lungs, and the diaphragm. When the diaphragm contracts, it creates a vacuum in the lungs that causes them to fill with air. During this inhalation, oxygen diffuses into the circulatory system while carbon dioxide diffuses out into the air that will be exhaled. The trachea branches out into two primary bronchi. Each bronchus is further divided into numerous secondary bronchi. These secondary bronchi further branch into tertiary bronchi. Finally, each tertiary bronchus branches into numerous bronchioles. Each bronchiole terminates into a tiny, sac-like structure known as an alveolus. The walls of each alveolus are thin and contain numerous blood capillaries. The process of gaseous exchange occurs in these alveoli. The diaphragm is a dome-shaped muscle situated at the lower end of the rib cage. It separates the abdominal cavity from the chest cavity. During inhalation, the diaphragm contracts, and the chest cavity enlarges, creating a vacuum that allows air to be drawn in. This causes the alveoli in the lungs to expand with air. During this process, oxygen diffuses into the circulatory system while carbon dioxide diffuses out into the air that will be exhaled. On the other hand, expansion of the diaphragm causes exhalation of air containing carbon dioxide. The Digestive System — The digestive system consists of the mouth, stomach, small intestine, large intestine, and anus. It is responsible for taking in food, digesting it to extract energy and nutrients that cells can use to function, and expelling the remaining waste material. Mechanical and chemical digestion takes place in the mouth and stomach, while absorption of nutrients and water takes place in the intestines. The digestive system begins at the mouth, where food is taken in, and ends at the anus, where waste is expelled. The food taken into the mouth breaks into pieces by the grinding action of the teeth. Carbohydrate digestion starts in the mouth with the breakdown of carbohydrates into simple sugars with the help of salivary enzymes. The chewed food, known as a bolus, enters the stomach through the esophagus. The bolus mixes with acids and enzymes released by the stomach. Protein digestion starts in the stomach as proteins are broken down into peptides. This partially digested food is known as chyme. Chyme enters the small intestine and mixes with bile, a substance secreted by the liver, along with enzymes secreted by the pancreas. The digestion of fats starts in the small intestine as bile and pancreatic enzymes break down fats into fatty acids. The surface of the small intestine consists of hair-like projections known as villi. These villi help in absorbing nutrients from the digested food. The digested food enters the large intestine, or colon, where water and salts are reabsorbed. Any undigested food is expelled out of the body as waste. The Skeletal System — The skeletal system is made up of over 200 bones. It protects the body's internal organs, provides support for the body and gives it shape, and works with the muscular system to move the body. In addition, bones can store calcium and produce red and white blood cells. The Muscular System — The muscular system includes more than 650 tough, elastic pieces of tissue. The primary function of any muscle tissue is movement. This includes the movement of blood through the arteries, the movement of food through the digestive tract, and the movement of arms and legs through space. Skeletal muscles relax and contract to move the bones of the skeletal system. The Excretory System — The excretory system removes excess water, dangerous substances, and wastes from the body. The excretory system also plays an important role in maintaining body equilibrium, or homeostasis. The human excretory system includes the lungs, sweat glands in the skin, and the urinary system (such as the kidneys and the bladder). The body uses oxygen for metabolic processes. Oxygen metabolism results in the production of carbon dioxide, which is a waste matter. The lungs expel carbon dioxide through the mouth and nose. The liver converts toxic metabolic wastes, such as ammonia, into less harmful susbtances. Ammonia is converted to urea, which is then excreted in the urine. The skin also expels urea and small amounts of ammonia through sweat. The skin is embedded with sweat glands. These glands secrete sweat, a solution of water, salt, and wastes. The sweat rises to the skin's surface, where it evaporates. The skin maintains homeostasis by producing sweat in hot environments. Sweat production cools and prevents excessive heating of the body. Each kidney contains about a million tiny structures called nephrons, which filter the blood and collect waste products, such as urea, salts, and excess water that go on to become urine. The Endocrine System — The endocrine system is involved with the control of body processes such as fluid balance, growth, and sexual development. The endocrine system controls these processes through hormones, which are produced by endocrine glands. Some endocrine glands include the pituitary gland, thyroid gland, parathyroid gland, adrenal glands, thymus gland, ovaries in females, and testes in males. The Immune System — The immune system is a network of cells, tissues, and organs that defends the body against foreign invaders. The immune system uses antibodies and specialized cells, such as T-cells, to defend the body from microorganisms that cause disease. The Reproductive System — The reproductive system includes structures, such as the uterus and fallopian tubes in females and the penis and testes in males, that allow humans to produce new offspring. The reproductive system also controls certain hormones in the human body that regulate the development of sexual characteristics and determine when the body is able to reproduce. The Integumentary System — The integumentary system is made up of a person's skin, hair, and nails. The skin acts as a barrier to the outside world by keeping moisture in the body and foreign substances out of the body. Nerves in the skin act as an interface with the outside world, helping to regulate important aspects of homeostasis, such as body temperature. Interacting Organ Systems The organ systems work together to perform complex bodily functions. The functions of regulation, nutrient absorption, defense, and reproduction are only possible because of the interaction of multiple body systems. Regulation All living organisms must maintain homeostasis, a stable internal environment. Organisms maintain homeostasis by monitoring internal conditions and making adjustments to the body systems as necessary. For example, as body temperature increases, skin receptors and receptors in a region of the brain called the hypothalamus sense the change. The change triggers the nervous system to send signals to the integumentary and circulatory systems. These signals cause the skin to sweat and blood vessels close to the surface of the skin to dilate, actions which dispel heat to decrease body temperature. Both the nervous system and the endocrine system are typically involved in the maintenance of homeostasis. The nervous system receives and processes stimuli, and then it sends signals to body structures to coordinate a response. The endocrine system helps regulate the response through the release of hormones, which travel through the circulatory system to their site of action. For example, the endocrine system regulates the level of sugar in the blood by the release of the hormones insulin, which stimulates uptake of glucose by cells, and glucagon, which stimulates the release of glucose by the liver. The nervous and endocrine systems interact with the excretory system in the process of osmoregulation, the homeostatic regulation of water and fluid balance in the body. The excretory system expels excess water, salts, and waste products. The excretion of excessive amounts of water can be harmful to the body because it reduces blood pressure. If the nervous system detects a decrease in blood pressure, it stimulates the endocrine system to release antidiuretic hormone. This hormone decreases the amount of water released by the kidneys to ensure appropriate blood pressure. Appropriate levels of carbon dioxide in the blood are also maintained by homeostatic mechanisms that involve several organ systems. Excess carbon dioxide, a byproduct of cellular respiration, can be harmful to an organism. As blood circulates throughout the body, it picks up carbon dioxide waste from cells and transports it to the lungs, where it is exhaled while fresh oxygen is inhaled. If the concentration of carbon dioxide in the blood increases above a certain threshold, the nervous system directs the lungs to increase their respiration rate to remove the excess carbon dioxide, which ensures that the levels of carbon dioxide in the blood are maintained at appropriate levels. In this way, the circulatory, respiratory, and nervous systems work together to limit the level of carbon dioxide in the blood. Nutrient Absorption To absorb nutrients from food, the nervous, digestive, muscular, excretory, and circulatory systems all interact. The nervous system controls the intake of food and regulates the muscular action of chewing, which mechanically breaks down food. As food travels through the stomach and intestines, the digestive system structures release enzymes to stimulate its chemical breakdown. At the same time, the muscular action, called peristalsis, of the muscles in the wall of the stomach help churn the food and push it through the digestive tract. In the intestines, nutrients from food travel across the surfaces of the villi. The nutrients are then picked up by the blood, and the circulatory system transports the nutrients throughout the cells of the body. The endocrine system releases hormones, such as insulin, that control the rate at which certain body cells use nutrients. Any excess minerals, such as calcium, in the blood are deposited in and stored by the skeletal system. Waste products produced by the use of nutrients, as well as the leftover solid waste from the digestion of food, exit the body through the excretory system. Throughout the process of nutrient absorption, the nervous system controls the muscles involved in digestion, circulation, and excretion. Defense Several body systems interact to defend the body from external threats. The body's first line of defense is the integumentary system, which provide a physical barrier that prevents pathogens from entering the body. The skin of the integumentary system also contains receptors for pain, temperature, and pressure. If an unpleasant stimulus is encountered, these receptors send signals to the central nervous system. In response, the central nervous system sends commands to the muscles to move the body part away from the stimulus. In this way, the integumentary, nervous, and muscular systems interact to prevent damage to the body. In the event of a break in the skin, the nervous, immune, lymphatic, and circulatory systems work together to repair the wound and protect the body from pathogens. When the skin is broken, specialized blood cells called platelets form a clot to stop the bleeding. These platelets also release chemicals that travel through the circulatory system and recruit cells, like immune system cells, to repair the wound. These immune cells, or white blood cells, are transported by the circulatory and lymphatic systems to the site of the wound, where they identify and destroy potentially pathogenic cells to prevent an infection. Some lymphocytes, white blood cells produced by the lymphatic system, also produce antibodies to neutralize specific pathogens. All of the white blood cells involved in the body's response were originally produced in the bone marrow of the skeletal system. If an infection does occur

Cytoplasm and Nuclear division

Cytoplasm

cytoplasm

5.1 Cytoplasm

WEEK 2:Cytology- The cytoplasm:

biology 2.1Unit 2.1: Mitosis and Meiosis Introduction By the end of this section, you should be able to: Define a chromosome. Define DNA as the genetic material. Define genes. Describe the structure of chromosomes. Describe the components of DNA. Define mitosis and describe its stages. Define meiosis and describe its stages. Relate the events of meiosis to the formation of sex cells. Compare mitosis and meiosis. Chromosomes, Genes, and DNA Almost all the cells of your body—except for mature red blood cells—contain a nucleus, which acts as the control center of the cell. The nucleus holds all the information needed to make a new cell and, ultimately, a new individual. Inside the nucleus are chromosomes, thread-like structures that store genetic information passed from parents to offspring. Chromosomes are made up of DNA (deoxyribonucleic acid), a molecule that carries the instructions needed to make all the proteins in your body. Many of these proteins are enzymes, which control the production of other chemicals and affect everything about how your body functions. Each species has a specific number of chromosomes: Humans have 46 chromosomes (23 pairs). Tomatoes have 24 chromosomes (12 pairs). Elephants have 56 chromosomes (28 pairs). Half of your chromosomes come from your mother, and the other half from your father. These chromosomes are arranged in homologous pairs, meaning they contain matching sets of genes. A karyotype is a special photograph that arranges chromosomes into their pairs. In humans, 22 pairs of chromosomes are called autosomes, which control most body functions. The 23rd pair is the sex chromosomes, which determine whether you are male or female: Females have two X chromosomes (XX). Males have one X and one Y chromosome (XY). DNA Structure DNA is a long, twisted molecule shaped like a double helix (a spiraled ladder). Each strand of DNA is made up of smaller molecules called nucleotides, which consist of: A phosphate group A sugar (deoxyribose) A nitrogen base The four nitrogen bases in DNA are: Adenine (A) → Always pairs with Thymine (T) Cytosine (C) → Always pairs with Guanine (G) Genes are small segments of DNA that carry instructions for making proteins. The sequence of these bases acts like a biological code, directing the cell to create specific proteins. In 1953, James Watson and Francis Crick, using data from Rosalind Franklin’s X-ray photographs, discovered the double-helix structure of DNA. Their discovery led to a huge increase in genetic research, including the Human Genome Project, which mapped all human genes. Mitosis (Cell Division for Growth and Repair) All body cells (somatic cells) divide using mitosis, a type of cell division that creates two identical daughter cells. Mitosis is essential for: Growth (producing new cells). Tissue repair (replacing damaged or old cells). Asexual reproduction (producing offspring with identical DNA). Stages of Mitosis Interphase The cell prepares for division by copying its DNA. Chromosomes are not visible under a microscope. Prophase Chromosomes condense and become visible. The nuclear membrane breaks down. Metaphase Chromosomes line up in the center of the cell. Spindle fibers attach to each chromosome. Anaphase The spindle fibers pull the sister chromatids apart to opposite ends of the cell. Telophase A new nuclear membrane forms around each set of chromosomes. The cell is almost ready to split. Cytokinesis The cytoplasm divides, forming two identical daughter cells. Mitosis is constantly occurring in areas like your skin and bone marrow, where new cells are needed regularly. Meiosis (Cell Division for Reproduction) Unlike mitosis, meiosis occurs only in the reproductive organs (testes in males, ovaries in females) and produces gametes (sperm and egg cells). Gametes have half the number of chromosomes (haploid, n=23) so that when fertilization occurs, the new cell has the correct chromosome number (diploid, 2n=46). Stages of Meiosis Meiosis consists of two rounds of cell division, resulting in four non-identical cells. Meiosis I: Prophase I – Chromosomes pair up and exchange genetic material (crossing over). Metaphase I – Chromosome pairs line up in the center of the cell. Anaphase I – Chromosome pairs separate and move to opposite ends of the cell. Telophase I & Cytokinesis – The cell splits into two haploid daughter cells. Meiosis II (similar to mitosis): 5. Prophase II – Chromosomes condense again. 6. Metaphase II – Chromosomes line up in the center. 7. Anaphase II – Sister chromatids separate and move to opposite sides. 8. Telophase II & Cytokinesis – Four unique haploid gametes are formed. Each gamete is genetically different due to crossing over and random chromosome distribution. Mitosis vs. Meiosis: Key Differences Importance of Mitosis and Meiosis Mitosis ensures that cells grow, repair damage, and replace old cells. Meiosis allows genetic diversity, which is essential for evolution and survival. Summary Chromosomes carry genetic information in the form of DNA. Genes are sections of DNA that code for proteins. Mitosis produces two identical daughter cells for growth and repair. Meiosis creates four non-identical sex cells for reproduction. Mitosis ensures genetic stability, while meiosis introduces genetic diversity

BIO207 Extranuclear/ Cytoplasmic/Organelle Inheritance

Lecture 3: Gram stain, Plasma membrane, and Cytoplasm

Lecture 6- Cytoplasm

BASIC STRUCTURE AND PROMINENT FUNCTIONS OF VERTEBRATE INTEGUMENT INTRODUCTION The integument or the outer cover of the body is commonly referred to as the skin. Together with its derivatives it makes up the integumentary system. It is continuous with the mucous membrane lining the mouth, eyelids, nostrils, rectum and the openings of the urino-genital ducts. The skin functions primarily to cover and protect the tissues lying beneath it. In other words, it forms the external protective covering of an animal. Forms interface between organism and external environment. Part that the predator sees first, and which offers the first line of defense. Abundantly supplied with sensory nerve endings, which are affected by environmental stimuli and play an important role in communication. General metabolism of the body, temperature regulation and water loss. Character of the skin and its derivatives shows variation in different regions of the body, in different individuals, in the same individual as age advances and in different groups of vertebrates. The type of environment whether aquatic or terrestrial is of importance in connection with these variations. The evolution of vertebrate integument is correlated with the transition of vertebrates from an aquatic to a terrestrial environment. Nevertheless, basic similarities exist in the integument of all vertebrates. INTEGUMENT PROPER In Annelids, Arthropods, integument consists of single layer of cells, the EPIDERMIS, together with an outer non-cellular CUTICLE, secreted by the cells. Annelids have a body covered with an external thin collagenous cuticle (never shed or molted). In Arthropods, the chitinous and rigid cuticle makes up the exoskeleton. Periodic shedding of this cuticle is termed Ecdysis. THE VERTEBRATE SKIN DIFFERS FROM INVERTEBRATE SKIN TWO LAYERS – Outer epidermis derived from ectoderm Inner dermis or corium of mesodermal origin. The relative amount of the two layers varies with the environment. EPIDERMIS – the epidermis is made of stratified epithelium (several layers of columnar epithelium cells). These cells are held together tightly by minute intercellular bridges found on the surface of cells. The innermost layer is stratum Malpighii or stratum germinativum placed over a thin basement membrane. These cells divide constantly to produce new cells. Move upwards, tend to become flattened, protoplasm becomes horny (keratinisation). In fishes and amphibians, this keratinised layer forms a cuticle, but in amniotes, it forms stratum corneum, of hard, horny, flat, cornified cells made largely of keratin, which is tough, waterproof and insoluble protein. It affords protection against mechanical injuries, fungal and bacterial attacks and prevents desiccation. In many Tetrapoda, this layer is shed periodically in pieces or all at once. No stratum corneum in cyclostomes and fishes (since they are fully aquatic) here the epidermis has mucous glands, secreting mucus to keep the skin slimy and protects it from bacteria. The epidermis has no blood vessels and is nourished by capillaries in the dermis. The epidermis rests on a thin basement membrane which separates it from the dermis Dermis has an outer loose layer and inner dense layer Made up of dense connective tissue having cells, muscles, blood vessels, lymph vessels, collagen and elastic fibres, and nerves. Amphibians and reptiles -collagen fibres at right angles in three planes Birds and mammals, they have an irregular arrangement. Substances pass by diffusion from the dermis to the epidermis. Skin contains pigment, if present in epidermis, it occurs as a diffuse substance or as granules. If in dermis, then in the form of granules in special branching cells called chromatophores. The pigment can either collect as a central ball making the skin lighter or spread out into all the branches making the skin darker, thus, chromatophores bring about colour variations. Chromatophores are of many kinds, Melanophores that contain brown to black pigment Lipophores or xanthophores which contain yellow red fatty pigments Iridocytes or guanophores contain crystals of guanine which reflect light. Under dermis, the skin has subcutaneous loose areolar tissue which separates the skin from the underlying muscles, it may contain fat and muscles, especially in mammals. Integument of Anamnia shows a decrease in thickness and also a decrease in the degree of ossification. These are of advantage in allowing greater mobility and in amphibians, they permit respiration by the skin. But in Amniota, the skin becomes progressively thicker to prevent loss of water and to retain body heat. STRUCTURE OF INTEGUMENT IN CYCLOSTOMATA Epidermis is multi-layered (stratified) but has no keratin. It has three types of unicellular gland cells: mucus glands (secrete mucus), club cells (scab-forming cells) and granular cells (unknown function). Below epidermis is the cutis formed of collagen and elastin fibres. Star- shaped pigment cells are also present in the cutis. STRUCTURE OF INTEGUMENT IN PISCES The epidermis has several layers of simple and thin cells, but there is no dead stratum corneum. The outermost cells are nucleated and living. The stratum Malpighii replenishes the outer layers of cells which have some keratin. Unicellular goblet or mucous gland cells are found in the epidermis, as in all aquatic animals. The mucous makes the skin slimy reducing friction between the body surface and water, protects the skin from bacteria and fungi and assists in the control of osmosis. Multicellular epidermal glands like poison glands and light producing organs may also be found. The epidermis rests on a delicate basement membrane. The dermis contains connective tissue, smooth muscles, blood vessels, nerves, lymph vessels and collagen fibres. The connective tissue fibres are generally not arranged at right angles but run parallel to the surface. Scales are embedded in the dermis and projected above the epidermal surface. The colours of fishes are due to chromatophores and iridocytes. STRUCTURE OF INTEGUMENT IN AMPHIBIA: The epidermis has several layers of cells, six to eight cells in thickness and is divisible into three layers: stratum corneum, stratum germinativum and a basal portion in contact with the basement membrane. The outermost layer is a stratum corneum, made of flattened, highly keratinised cells. Such a dead layer appears first in amphibians and is best formed in those which spend a considerable time on land. The stratum corneum is an adaptation to terrestrial life (protects body and prevents excessive loss of moisture). In ecdysis, stratum corneum is cast off in fragments or as a whole in some. (moulting / desquamation i.e., removal of unicellular sheet of stratum corneum). The dermis is relatively thin in amphibians, it is made of two layers - upper loose stratum spongiosum and a lower dense and compact stratum compactum. Connective tissue fibres run both vertically and horizontally. Blood vessels, lymph spaces, glands and nerves are abundant in the stratum spongiosum. There are two kinds of glands, multicellular mucous glands and poison glands in the dermis, but they are derivatives of the epidermis. Mucous gland produces mucus (slimy protective covering, helps in respiration). Amphibian skin is an important organ of respiration. Poison glands produce a mild but unpleasant poison which is protective. In the upper part of the dermis are chromatophores. (melanophores and lipophores) Ability of the skin for changing colour to blend with the environment is well developed. INTEGUMENT IN REPTILIA. The integument is thick and dry, it prevents any loss of water, it has almost no glands. The only glands present are scent glands for sexual activity. The epidermis has a well-developed stratum corneum well adapted to terrestrial life. The horny scales of reptiles are derived from this layer. Ecdysis is necessary to remove dead outer layers, hence scales are shed periodically in fragments or cast in a single slough as in snakes and some lizards Scales often form spines or crests. Below the epidermal scales are dermal bony plates or osteoderms in tortoises, crocodiles and some lizards (Heloderma). The dermis is thick and has an upper layer and a lower layer, upper layer has abundance of chromatophores in snakes and lizards. Lower layer has bundles of connective tissue in which collagen fibres lie at right angles. Leather of high commercial value can be prepared from the skin of many reptiles like lizards, snakes and crocodiles. Many lizards and snakes have elaborate colour patterns, they may be for concealment or as warning colours. There is marked colour change in certain lizards such as chameleon, the colour may change with the environment for concealment or it may change in courtship or threat. The ability of chameleons and some other animals to change colour is known as metachrosis. (metachromatism) In Calotes, chromatophores are controlled by the posterior lobe of pituitary whereas in chameleons they are controlled by the Autonomic Nervous System. INTEGUMENT IN BIRDS Thin, loose, dry and devoid of glands. There is only a uropygial gland at the base of the tail, its oil is used for preening (to clean and tidy its feathers with its beak) and waterproofing the feathers (aquatic birds) Epidermis is delicate except on shanks and feet where it is thick and forms epidermal scales. The rest of the body has a protective covering of epidermal feathers. The keratin producing powers of the epidermis are devoted to producing feathers and scales. The dermis is thin and has interlacing connective tissue fibres, abundant muscle fibres for moving feathers, blood vessels and nerves. The dermis has an upper and lower compact layer, between which is a vascular layer, the dermis also contains fat cells. The skin has no chromatophores. Pigment is found only in feathers and scales. Colour patterns in birds are vivid (concealment, recognition and sexual stimulation) Colours are produced partly by pigments and partly by reflection and refraction from the surface of the feathers. INTEGUMENT IN MAMMALS Skin is elastic and waterproof, much thicker than in other animals, especially the dermis is very thick and is used in making leather. Epidermis is thickest in mammals. Outer stratum corneum containing keratin, cells not dead as believed before. Below this is stratum lucidum (barrier layer), chemical called eleidin Below this stratum granulosum, darkly staining granules of keratohyalin Below this is stratum spinosum whose cells are held together by spiny intercellular bridges. Lastly stratum germinativum which rests on a basement membrane Dermis is best developed in mammals. Upper layer is papillary layer made up of elastic and collagen fibres with capillaries in-between, thrown into folds called dermal papillae, especially in areas of friction Greater lower part of dermis is reticular layer, having elastic and collagen fibres. In both layers there are blood vessels, nerves smooth muscles, certain glands tactile corpuscles and connective tissue fibres in all directions. Below dermis the subcutaneous tissue contains a layer of fat cells forming adipose tissue In the lowest layer of epidermis there are pigment granules, no pigment bearing chromatophores in mammaIs (in man, branching dendritic cells or melanoblasts) FUNCTIONS OF THE INTEGUMENT ▪ PROTECTION ▪ TEMPERATURE CONTROL ▪ FOOD STORAGE ▪ SECRETION ▪ EXCRETION ▪ SENSATION ▪ RESPIRATION ▪ LOCOMOTION ▪ DERMAL ENDOSKELETON ▪ SEXUAL SELECTION 1. Protection: The integument forms a covering of the body and is protective. It protects the body against entry of foreign bodies and against mechanical injuries. It protects the tissues against excessive loss of moisture, this is very important because both aquatic and terrestrial animals are dependent upon water in their bodies for various metabolic activities. The integument forms protective derivatives, such as scales, bony plates, layer of fat, feathers and hair which reduce the effect of injurious contacts. In some animals the skin shows protective colouration which makes the animals resemble their environment, thus, making them almost invisible to their enemies. Poison glands of toads, slippery skin of aquatic animals and an armour of spines of some mammals are protective devices of the integument. The skin forms a covering which prevents the passage of water and solutes in one of the following ways: (a) By formation of cuticle in Protochordata and embryos of fishes and amphibians, (b) By secreting a coat of mucus in fishes and aquatic amphibians, and (c) By formation of keratin layers in the epidermis of tetrapoda. Keratin is formed from the cytoplasm of degenerating cells of the epidermis which finally form a layer of horny stratum corneum. 2. Temperature Control: Heat is produced constantly by oxidation of food stuffs in tissues. This heat is distributed evenly by the circulating blood. The body heat is lost constantly with expired breath, with faeces and urine, and from the surface of the skin. The integument regulates heat and maintains a constant temperature in endothermal animals. In birds the heat is regulated by adjustment of feathers which retain a warm blanket of air, when feathers are held close to the body, they remove warm air and body cooled, when feathers are fluffed out, they keep the warm air enclosed. In mammals, constant evaporation of sweat regulates the body heat. In cold weather contraction of skin’s blood capillaries reduces the loss of body heat. In some animals, fat in the skin prevents loss of heat because it is a non-conductor of heat. 3. Food Storage: The skin stores fat in its layers as reserve food material which is used for nourishment in times of need. In whales and seals the fat of the skin forms a thick layer, called blubber which is not only reserve food but also maintains the body temperature. 4. Secretion: The skin acts as an organ of secretion. Glands of the skin are secretory. In aquatic forms there are secretory mucous glands whose secretions keep the skin moist and slippery. In mammals, sebaceous glands secrete oil which lubricates the skin and hairs. Mammary glands produce milk for nourishment of the young. In birds uropygial glands secrete oil for preening the feathers. Odours of scent glands attract the opposite sex. Lacrymal glands’ secretion wash the conjunctiva of eyeball in mammals. Ear wax (cerumen) secreted by the glands of auditory meatus greases the eardrums and avoids insects to enter the canal. 5. Excretion: The integument acts as an organ of excretion. Shedding of the corneal layer during ecdysis removes some waste substances. In mammals metabolic waste (salts, urea and water) is removed from the blood by means of sweat. Chloride secreting cells are found in gills of marine fishes. 6. Sensation: The skin is an important sense organ because it has various kinds of tactile cells and corpuscles which are sensory to touch, temperature changes, heat, cold, pressure and pain. 7. Respiration: In amphibians, the moist skin acts as an organ of respiration, in frogs the respiratory function of the skin is greater than that of the lungs. 8. Locomotion: Derivatives of the integument bring about locomotion in some animals, such as the fins of fishes aid in locomotion in water, the web of skin in the feet of frogs and aquatic birds aid in swimming, feathers of the wings and tail of birds are used for flying, and extensions of the integument forming “wings” of flying lizards, extinct pterodactyls, flying squirrels and bats. 9. Dermal Endoskeleton: The skin contributes to the endoskeleton. It forms the dermal bones of vertebrates and also forms parts of the teeth. Endoskeleton of head protects the brain and sense organs. In the body it protects the soft, tender viscera. 10. Sexual Selection: The skin acts as an organ of sexual selection. It provides the feathers of birds which often have brilliant colours which are for sexual attraction. Some integumentary glands of mammals produce odours far attracting the opposite sex. Antlers of male deer distinguish it from female. Besides the above functions, mammalian skin synthesizes the vitamin D with the help of Sebum of sebaceous glands. Brood pouches beneath skin in some fishes and amphibians protect unhatched eggs. Nasal glands of tetrapods, keep the nostrils free of dirt and water. Skin also has the power of absorption of oils, ointments, etc

A&P Cytoplasmic Organelles

endomembrane system Semi-autonomous organelles Protein sorting to organelles Systems biology of cells Cell Biology & Cell Theory Cell biology: The study of individual cells and their interactions. Cell Theory (Schleiden & Schwann, with contributions from Virchow): All living organisms are composed of one or more cells. Cells are the smallest units of life. New cells arise only from pre-existing cells through division (e.g., binary fission). Origins of Life: Four Overlapping Stages Stage 1: Formation of Organic Molecules Primitive Earth conditions favored spontaneous organic molecule formation. Hypotheses on the origin of organic molecules: Reducing Atmosphere Hypothesis: Earth's early atmosphere (rich in water vapor) facilitated molecule formation. Stanley Miller’s experiment simulated early conditions, producing amino acids and sugars. Extraterrestrial Hypothesis: Organic carbon (amino acids, nucleic acid bases) may have come from meteorites. Debate exists over survival after intense heating. Deep-Sea Vent Hypothesis: Molecules formed in the temperature gradient between hot vent water & cold ocean water. Supported by experimental evidence. Alkaline hydrothermal vents may have created pH gradients that allowed organic molecule formation. Stage 2: Formation of Polymers Early belief: Prebiotic synthesis of polymers was unlikely in aqueous solutions (water competes with polymerization). Experimental evidence: Clay surfaces facilitated the formation of nucleic acid polymers and polysaccharides. Stage 3: Formation of Boundaries Protobionts: Aggregates of prebiotically produced molecules enclosed by membranes. Characteristics of a protobiont: Boundary separating the internal & external environments. Polymers with information (e.g., genetic material, metabolic instructions). Catalytic functions (enzymatic activities). Self-replication. Liposomes: Vesicles surrounded by lipid bilayers. Can enclose RNA and divide. Stage 4: RNA World Hypothesis RNA was likely the first macromolecule in protobionts due to its ability to: Store information. Self-replicate. Catalyze reactions (ribozymes). Chemical Selection & Evolution: RNA mutations allowed faster replication & self-sufficient nucleotide synthesis. Eventually, RNA world was replaced by the DNA-RNA-protein world due to: DNA providing more stable information storage. Proteins offering greater catalytic efficiency and specialized functions. Microscopy Microscopy Parameters Resolution: Ability to distinguish two adjacent objects. Contrast: Difference between structures (enhanced by special dyes). Magnification: Ratio of image size to actual size. Types of Microscopes Light Microscope: Uses light; resolution = 0.2 micrometers. Electron Microscope: Uses electron beams; resolution = 2 nanometers (100x better than light microscopes). Light Microscopy Subtypes Bright Field: Standard; light passes directly through. Phase Contrast: Amplifies differences in light phase shifts. Differential Interference Contrast (DIC): Enhances contrast for internal structures. Electron Microscopy Subtypes Transmission Electron Microscopy (TEM): Thin slices stained with heavy metals. Some electrons scatter while others pass through to create an image. Scanning Electron Microscopy (SEM): Heavy metal-coated sample. Electron beam scans the surface, producing 3D images. Cell Structure & Function Determined by matter, energy, organization, and information. Genome: The complete set of genetic material. Prokaryotic vs. Eukaryotic Cells Feature Prokaryotic Cells Eukaryotic Cells Nucleus ❌ Absent ✅ Present Membrane-bound organelles ❌ None ✅ Yes Size Small (1-10 µm) Large (10-100 µm) Examples Bacteria, Archaea Plants, Animals, Fungi, Protists Prokaryotic Cell Structure Plasma Membrane: Lipid bilayer barrier. Cytoplasm: Internal fluid. Nucleoid Region: DNA storage (no nucleus). Ribosomes: Protein synthesis. Cell Wall: (Some) Provides structure & protection. Glycocalyx: Protection & hydration. Flagella: Movement. Pili: Attachment. Eukaryotic Cell Structure Nucleus: Contains DNA & controls cell functions. Organelles: Rough ER: Protein synthesis & sorting. Smooth ER: Lipid synthesis, detoxification. Golgi Apparatus: Protein modification & sorting. Mitochondria: ATP production (Powerhouse of the Cell™). Lysosomes: Digestive enzymes for breakdown & recycling. Peroxisomes: Breakdown of harmful substances. Cytoskeleton: Provides structure (microtubules, actin filaments, intermediate filaments). Plasma Membrane: Regulates transport & signaling. Endomembrane System Includes: Nucleus, ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane. Nuclear Envelope: Double membrane structure. Nuclear pores allow molecule transport. Golgi Apparatus: Modifies & sorts proteins/lipids. Packages proteins into vesicles for secretion (exocytosis). Lysosomes: Contain acid hydrolases for macromolecule breakdown. Perform autophagy (organelle recycling). Semi-Autonomous Organelles Mitochondria Function: ATP production (cellular respiration). Structure: Outer & inner membrane (inner folds = cristae for increased surface area). Mitochondrial matrix houses metabolic enzymes. Chloroplasts (Plants & Algae) Function: Photosynthesis (light energy → chemical energy). Structure: Outer & inner membrane. Thylakoid membrane (site of photosynthesis). Contains chlorophyll. Endosymbiosis Theory Mitochondria & chloroplasts evolved from free-living bacteria that were engulfed by an ancestral eukaryotic cell. Protein Sorting & Cell Organization Co-translational sorting: Proteins destined for ER, Golgi, lysosomes, vacuoles, or secretion. Post-translational sorting: Proteins sent to nucleus, mitochondria, chloroplasts, peroxisomes. Systems Biology Studies how cellular components interact to form a functional system

Histology Cytoplasm

Prok. Cells: Gram Stain, PM & Cytoplasm

Cytoplasmic Organelles

BIOLOGY - CYTOPLASM

Lecture 6: Nucleo-Cytoplasmic Transport Part II