Notes, summaries, assignments, exams, and problems for Biology

Tendon Structure

Tendon: A structure composed of collagen fibers arranged parallel to the tendon's axis. These fibers are designed for low flexibility and resistance to extension. Within the tendon, we find loose connective tissue and cells called tenocytes.

The entire structure is termed the endotendon, enclosed within a sheath called the peritenon. The peritenon's extension is continuous with the periosteum at one end and the perimysium at the other.

Some tendinous fibers, known as Sharpey's fibers, penetrate the bone and calcify, forming a strong union between tendon and bone.

The tendon is protected by an outer sleeve consisting of a parietal layer and an inner visceral synovial layer. A space filled with synovial fluid separates these layers.... Continue reading "Tendon, Fascia, and Cranial Bones: Structure and Function" »

NADP⁺ acts as a powerful reducing agent, carrying hydrogen atoms essential for reducing carbon compounds and facilitating the formation of ATP and carbohydrates. NADP⁺ and ATP are also crucial for nitrogen assimilation during photosynthesis, leading to the synthesis of amino acids. Nitrogen, assimilated as nitrates and nitrites dissolved in the crude sap, is transported to plant tissues. Similarly, sulfur, obtained from sulfates and sulfites, is fixed to form the sulfhydryl (-SH) group of amino acids like cysteine. This process of incorporating bioelements, including phosphorus, into organic molecules is fundamental for plant life.

Carbon Fixation in the Dark Phase (Fig. 12, p. 184)

The fixation of carbon from CO₂ follows a cyclic pathway known... Continue reading "Photosynthesis Dark Reactions: Carbon & Nitrogen Assimilation" »

Nervous vs. Endocrine System Coordination

Living organisms utilize different systems for coordination. These include:

• Nervous System: Receives information and processes it for a fast response. It utilizes nerve impulses, and its effects are generally short-lasting.
• Endocrine System: Elaborates hormones for communication. Its response is typically very slow but durable.

Nervous System Response Pathway

The nervous system's response to stimuli involves several key components:

Receptor, Center, and Effector

• Receptor: The organ or structure responsible for perceiving stimuli from the internal or external environment.
• Nervous Center: Receives information from receptors and transmits processed information, producing a series of organized responses.
• Effector:

Understanding Kartagener Syndrome

Kartagener syndrome is a rare genetic disorder, believed to follow an autosomal recessive inheritance pattern, with an incidence of approximately 1 in 20,000 live births.

Key Characteristics and Manifestations

This condition is one of the primary ciliary dyskinesia (PCD) syndromes, a group of disorders characterized by structural or functional alterations of cilia. These changes affect all ciliated epithelia in the body, including the respiratory epithelium (found in the sinuses and Eustachian tube) and sperm. This leads to impaired mucus clearance and retention.

Typically, Kartagener syndrome is characterized by a classic triad of symptoms:

• Situs Inversus (complete or partial): A rare anatomical abnormality where

Cranial Bones

Frontal Bone

The Frontal Bone is an unpaired, flat bone located on the top and front of the head. It forms the "roof" of the orbits and the root of the nose.

Sphenoid Bone

The Sphenoid Bone is an unpaired bone located in the anterior base of the skull. It has a body and six extensions: two greater wings, two lesser wings, and two pterygoid processes. Through these, it is inserted like a wedge between the other bones of the skull.

Occipital Bone

The Occipital Bone is an unpaired bone located posteroinferiorly in the skull. Its lowest part, which forms part of the skull base, features the foramen magnum. This opening connects the cranial cavity, housing the brain, to the spinal canal, which contains the spinal cord, thus allowing the... Continue reading "Human Skull Bones: Anatomy and Functions" »

The Human Circulatory System

Blood Vessels: Arteries, Veins, and Capillaries

• Arteries: Blood flows from the heart to all other organs of the body. Walls are thicker and more elastic to withstand the high pressure with which blood flows, driven by the heart.
• Veins: Blood flows from the various organs back to the heart. The walls are thin and less elastic than the arteries as blood circulates under less pressure.
• Capillaries: Microscopic vessels that connect like a network, linking the endings of the arteries with the start of the veins.

Essential Components of Blood

There are three main blood types.

Plasma

The liquid, straw-colored component built of 90% water. It contains a variety of dissolved substances, including various proteins, carbohydrates... Continue reading "Anatomy and Function of the Human Circulatory System" »

Anatomical Planes

Anatomical planes are imaginary lines drawn through the body in the standard anatomical position. They serve to guide and define the position of organs and structures, providing a universal reference system for describing the human body.

Coronal (Frontal) Plane

This vertical plane divides the body into anterior (front) and posterior (back) sections.

Sagittal Plane

This vertical plane divides the body into left and right sections. A midsagittal (or median) plane specifically divides the body into equal left and right halves.

Transverse (Axial or Horizontal) Plane

This horizontal plane divides the body into superior (upper) and inferior (lower) sections.

Anatomical Directional Terminology

These terms describe the relative positions of... Continue reading "Essential Anatomical Planes, Terms, and Body Cavities" »

Vertebrate Nervous System: Structure and Components

Vertebrates possess a tubular nervous system, consisting of the brain and spinal cord.

Central Nervous System (CNS)

The Central Nervous System (CNS) consists of the brain and spinal cord. It is protected by two main types of envelopes:

• Bony Envelopes: The skull and vertebrae.
• Membranous Envelopes (Meninges): These consist of three layers: the dura mater, arachnoid mater, and pia mater. The cerebrospinal fluid (CSF) is located between the last two layers, functioning to cushion impacts.

Nerve fibers are grouped, forming the white matter. In the brain, the gray matter is located in the periphery (cortex), while the white matter is internal.

The Brain

The brain is composed of several major regions:

• Telencephalon

Nucleic Acids: Life's Genetic Blueprint

What Are Nucleic Acids?

Nucleic acids are vital macromolecules that store and transmit genetic information. They are polymers formed by the union of repeating monomeric units called nucleotides.

Understanding Nucleotides: Building Blocks

Nucleotides, the fundamental components of nucleic acids, are composed of three parts:

• Carbohydrate (Pentose Sugar): This is a five-carbon sugar. In RNA (Ribonucleic Acid), the sugar is ribose. In DNA (Deoxyribonucleic Acid), the sugar is deoxyribose.
• Phosphate Group (P): A molecule containing phosphorus and oxygen.
• Nitrogenous Base (BN): A nitrogen-containing molecule with basic properties. The main nitrogenous bases are:
  • Adenine (A)
  • Guanine (G)
  • Cytosine (C)
  • Thymine (T) - primarily